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<pre>Internet Engineering Task Force (IETF)                           W. Wang
Request for Comments: 6956                 Zhejiang Gongshang University
Category: Standards Track                                  E. Haleplidis
ISSN: 2070-1721                                     University of Patras
                                                                K. Ogawa
                                                         NTT Corporation
                                                                   C. Li
                                                         Hangzhou DPtech
                                                              J. Halpern
                                                                Ericsson
                                                               June 2013


           <span class="h1">Forwarding and Control Element Separation (ForCES)</span>
                  <span class="h1">Logical Function Block (LFB) Library</span>

Abstract

   This document defines basic classes of Logical Function Blocks (LFBs)
   used in Forwarding and Control Element Separation (ForCES).  The
   basic LFB classes are defined according to the ForCES Forwarding
   Element (FE) model and ForCES protocol specifications; they are
   scoped to meet requirements of typical router functions and are
   considered the basic LFB library for ForCES.  The library includes
   the descriptions of the LFBs and the XML definitions.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in <a href="./rfc5741#section-2">Section&nbsp;2 of RFC 5741</a>.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   <a href="http://www.rfc-editor.org/info/rfc6956">http://www.rfc-editor.org/info/rfc6956</a>.












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Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   <a href="#section-1">1</a>. Introduction ....................................................<a href="#page-3">3</a>
   <a href="#section-2">2</a>. Terminology and Conventions .....................................<a href="#page-4">4</a>
      <a href="#section-2.1">2.1</a>. Requirements Language ......................................<a href="#page-4">4</a>
      <a href="#section-2.2">2.2</a>. Definitions ................................................<a href="#page-4">4</a>
   <a href="#section-3">3</a>. Overview ........................................................<a href="#page-6">6</a>
      <a href="#section-3.1">3.1</a>. Scope of the Library .......................................<a href="#page-6">6</a>
      <a href="#section-3.2">3.2</a>. Overview of LFB Classes in the Library .....................<a href="#page-8">8</a>
           <a href="#section-3.2.1">3.2.1</a>. LFB Design Choices ..................................<a href="#page-8">8</a>
           <a href="#section-3.2.2">3.2.2</a>. LFB Class Groupings .................................<a href="#page-9">9</a>
           <a href="#section-3.2.3">3.2.3</a>. Sample LFB Class Application .......................<a href="#page-10">10</a>
      <a href="#section-3.3">3.3</a>. Document Structure ........................................<a href="#page-11">11</a>
   <a href="#section-4">4</a>. Base Types .....................................................<a href="#page-11">11</a>
      <a href="#section-4.1">4.1</a>. Data Types ................................................<a href="#page-13">13</a>
           <a href="#section-4.1.1">4.1.1</a>. Atomic .............................................<a href="#page-13">13</a>
           <a href="#section-4.1.2">4.1.2</a>. Compound Struct ....................................<a href="#page-13">13</a>
           <a href="#section-4.1.3">4.1.3</a>. Compound Array .....................................<a href="#page-14">14</a>
      <a href="#section-4.2">4.2</a>. Frame Types ...............................................<a href="#page-14">14</a>
      <a href="#section-4.3">4.3</a>. Metadata Types ............................................<a href="#page-15">15</a>
      <a href="#section-4.4">4.4</a>. XML for Base Type Library .................................<a href="#page-16">16</a>
   <a href="#section-5">5</a>. LFB Class Descriptions .........................................<a href="#page-41">41</a>
      <a href="#section-5.1">5.1</a>. Ethernet-Processing LFBs ..................................<a href="#page-42">42</a>
           <a href="#section-5.1.1">5.1.1</a>. EtherPHYCop ........................................<a href="#page-42">42</a>
           <a href="#section-5.1.2">5.1.2</a>. EtherMACIn .........................................<a href="#page-44">44</a>
           <a href="#section-5.1.3">5.1.3</a>. EtherClassifier ....................................<a href="#page-46">46</a>
           <a href="#section-5.1.4">5.1.4</a>. EtherEncap .........................................<a href="#page-48">48</a>
           <a href="#section-5.1.5">5.1.5</a>. EtherMACOut ........................................<a href="#page-50">50</a>
      <a href="#section-5.2">5.2</a>. IP Packet Validation LFBs .................................<a href="#page-52">52</a>
           <a href="#section-5.2.1">5.2.1</a>. IPv4Validator ......................................<a href="#page-52">52</a>
           <a href="#section-5.2.2">5.2.2</a>. IPv6Validator ......................................<a href="#page-54">54</a>





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      <a href="#section-5.3">5.3</a>. IP Forwarding LFBs ........................................<a href="#page-55">55</a>
           <a href="#section-5.3.1">5.3.1</a>. IPv4UcastLPM .......................................<a href="#page-56">56</a>
           <a href="#section-5.3.2">5.3.2</a>. IPv4NextHop ........................................<a href="#page-58">58</a>
           <a href="#section-5.3.3">5.3.3</a>. IPv6UcastLPM .......................................<a href="#page-60">60</a>
           <a href="#section-5.3.4">5.3.4</a>. IPv6NextHop ........................................<a href="#page-62">62</a>
      <a href="#section-5.4">5.4</a>. Redirect LFBs .............................................<a href="#page-64">64</a>
           <a href="#section-5.4.1">5.4.1</a>. RedirectIn .........................................<a href="#page-64">64</a>
           <a href="#section-5.4.2">5.4.2</a>. RedirectOut ........................................<a href="#page-65">65</a>
      <a href="#section-5.5">5.5</a>. General Purpose LFBs ......................................<a href="#page-66">66</a>
           <a href="#section-5.5.1">5.5.1</a>. BasicMetadataDispatch ..............................<a href="#page-66">66</a>
           <a href="#section-5.5.2">5.5.2</a>. GenericScheduler ...................................<a href="#page-68">68</a>
   <a href="#section-6">6</a>. XML for LFB Library ............................................<a href="#page-69">69</a>
   <a href="#section-7">7</a>. LFB Class Use Cases ............................................<a href="#page-97">97</a>
      <a href="#section-7.1">7.1</a>. IPv4 Forwarding ...........................................<a href="#page-98">98</a>
      <a href="#section-7.2">7.2</a>. ARP Processing ...........................................<a href="#page-101">101</a>
   <a href="#section-8">8</a>. IANA Considerations ...........................................<a href="#page-102">102</a>
      <a href="#section-8.1">8.1</a>. LFB Class Names and LFB Class Identifiers ................<a href="#page-103">103</a>
      <a href="#section-8.2">8.2</a>. Metadata ID ..............................................<a href="#page-105">105</a>
      <a href="#section-8.3">8.3</a>. Exception ID .............................................<a href="#page-106">106</a>
      <a href="#section-8.4">8.4</a>. Validate Error ID ........................................<a href="#page-107">107</a>
   <a href="#section-9">9</a>. Security Considerations .......................................<a href="#page-108">108</a>
   <a href="#section-10">10</a>. References ...................................................<a href="#page-108">108</a>
      <a href="#section-10.1">10.1</a>. Normative References ....................................<a href="#page-108">108</a>
      <a href="#section-10.2">10.2</a>. Informative References ..................................<a href="#page-108">108</a>
   <a href="#appendix-A">Appendix A</a>.  Acknowledgements ....................................<a href="#page-110">110</a>
   <a href="#appendix-B">Appendix B</a>.  Contributors ........................................<a href="#page-110">110</a>

<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>.  Introduction</span>

   [<a id="ref-RFC3746">RFC3746</a>] specifies the Forwarding and Control Element Separation
   (ForCES) framework.  In the framework, Control Elements (CEs)
   configure and manage one or more separate Forwarding Elements (FEs)
   within a Network Element (NE) by use of a ForCES protocol.  [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>]
   specifies the ForCES protocol.  [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>] specifies the Forwarding
   Element (FE) model.  In the model, resources in FEs are described by
   classes of Logical Function Blocks (LFBs).  The FE model defines the
   structure and abstract semantics of LFBs and provides XML schema for
   the definitions of LFBs.

   This document conforms to the specifications of the FE model
   [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>] and specifies detailed definitions of classes of LFBs,
   including detailed XML definitions of LFBs.  These LFBs form a base
   LFB library for ForCES.  LFBs in the base library are expected to be
   combined to form an LFB topology for a typical router to implement IP
   forwarding.  It should be emphasized that an LFB is an abstraction of
   functions rather than implementation details.  The purpose of the LFB
   definitions is to represent functions so as to provide
   interoperability between separate CEs and FEs.



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   More LFB classes with more functions may be developed in the future
   and documented by the IETF.  Vendors may also develop proprietary LFB
   classes as described in the FE model [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>].

<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>.  Terminology and Conventions</span>

<span class="h3"><a class="selflink" id="section-2.1" href="#section-2.1">2.1</a>.  Requirements Language</span>

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [<a href="./rfc2119" title="&quot;Key words for use in RFCs to Indicate Requirement Levels&quot;">RFC2119</a>].

<span class="h3"><a class="selflink" id="section-2.2" href="#section-2.2">2.2</a>.  Definitions</span>

   This document follows the terminology defined by the ForCES protocol
   in [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>] and by the ForCES FE model in [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>].  The
   definitions below are repeated for clarity.

      Control Element (CE) - A logical entity that implements the ForCES
      protocol and uses it to instruct one or more FEs on how to process
      packets.  CEs handle functionality such as the execution of
      control and signaling protocols.

      Forwarding Element (FE) - A logical entity that implements the
      ForCES protocol.  FEs use the underlying hardware to provide per-
      packet processing and handling as directed/controlled by one or
      more CEs via the ForCES protocol.

      ForCES Network Element (NE) - An entity composed of one or more
      CEs and one or more FEs.  To entities outside an NE, the NE
      represents a single point of management.  Similarly, an NE usually
      hides its internal organization from external entities.

      Logical Function Block (LFB) - The basic building block that is
      operated on by the ForCES protocol.  The LFB is a well-defined,
      logically separable functional block that resides in an FE and is
      controlled by the CE via the ForCES protocol.  The LFB may reside
      at the FE's data path and process packets or may be purely an FE
      control or configuration entity that is operated on by the CE.
      Note that the LFB is a functionally accurate abstraction of the
      FE's processing capabilities but not a hardware-accurate
      representation of the FE implementation.

      FE Model - The FE model is designed to model the logical
      processing functions of an FE, which is defined by the ForCES FE
      model document [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>].  The FE model proposed in this document
      includes three components: the LFB modeling of individual Logical
      Functional Blocks (LFB model), the logical interconnection between



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      LFBs (LFB topology), and the FE-level attributes, including FE
      capabilities.  The FE model provides the basis to define the
      information elements exchanged between the CE and the FE in the
      ForCES protocol [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>].

      FE Topology - A representation of how the multiple FEs within a
      single NE are interconnected.  Sometimes this is called inter-FE
      topology, to be distinguished from intra-FE topology (i.e., LFB
      topology).

      LFB Class and LFB Instance - LFBs are categorized by LFB classes.
      An LFB instance represents an LFB class (or type) existence.
      There may be multiple instances of the same LFB class (or type) in
      an FE.  An LFB class is represented by an LFB class ID, and an LFB
      instance is represented by an LFB instance ID.  As a result, an
      LFB class ID associated with an LFB instance ID uniquely specifies
      an LFB existence.

      LFB Metadata - Metadata is used to communicate per-packet state
      from one LFB to another but is not sent across the network.  The
      FE model defines how such metadata is identified, produced, and
      consumed by the LFBs.  It defines the functionality but not how
      metadata is encoded within an implementation.

      LFB Component - Operational parameters of the LFBs that must be
      visible to the CEs are conceptualized in the FE model as the LFB
      components.  The LFB components include, for example, flags,
      single parameter arguments, complex arguments, and tables that the
      CE can read and/or write via the ForCES protocol (see below).

      LFB Topology - Representation of how the LFB instances are
      logically interconnected and placed along the data path within one
      FE.  Sometimes it is also called intra-FE topology, to be
      distinguished from inter-FE topology.

      Data Path - A conceptual path taken by packets within the
      forwarding plane inside an FE.  Note that more than one data path
      can exist within an FE.

      ForCES Protocol - While there may be multiple protocols used
      within the overall ForCES architecture, the term "ForCES protocol"
      and "protocol" refer to the Fp reference points in the ForCES
      framework in [<a href="./rfc3746" title="&quot;Forwarding and Control Element Separation (ForCES) Framework&quot;">RFC3746</a>].  This protocol does not apply to CE-to-CE
      communication, FE-to-FE communication, or to communication between
      FE and CE managers.  Basically, the ForCES protocol works in a
      master-slave mode in which FEs are slaves and CEs are masters.





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      Physical Port - A port refers to a physical media input port or
      output port of an FE.  A physical port is usually assigned with a
      physical port ID, abbreviated with a PHYPortID.  This document
      mainly deals with physical ports with Ethernet media.

      Logical Port - A conceptually virtual port at the data link layer
      (L2) or network layer (L3).  A logical port is usually assigned
      with a logical port ID, abbreviated with a LogicalPortID.  The
      logical ports can be further categorized with an L2 logical port
      or an L3 logical port.  An L2 logical port can be assigned with an
      L2 logical port ID, abbreviated with an L2PortID.  An L3 logical
      port can be assigned with an L3 logical port ID, abbreviated with
      an L3PortID.  MAC-layer VLAN ports belong to logical ports, and
      they belong to L2 logical ports.

      LFB Port - The connection points where one LFB can be connected to
      another within an FE.  As described in [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>], the CE can
      connect LFBs together by establishing connections between an
      output port of one LFB instance and an input port of another LFB
      instance.  Also see <a href="./rfc5812#section-3.2">Section&nbsp;3.2 of [RFC5812]</a> for more details.

      Singleton Port - A named input or output port of an LFB.  This
      port is referred to by a name.  When the context is clear, the
      term "singleton" by itself is used to refer to a singleton port.

      Group Port - A named collection of input or output ports of an
      LFB.  A group port is referred to by a name.  A group port
      consists of a number of port instances, which are referred to by a
      combination of a name and an index.

      LFB Class Library - The LFB class library is a set of LFB classes
      that has been identified as the most common functions found in
      most FEs and hence should be defined first by the ForCES Working
      Group.  The LFB class library is defined by this document.

<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>.  Overview</span>

<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>.  Scope of the Library</span>

   It is intended that the LFB classes described in this document are
   designed to provide the functions of a typical router.  [<a href="./rfc1812" title="&quot;Requirements for IP Version 4 Routers&quot;">RFC1812</a>]
   specifies that a typical router is expected to provide functions to:









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   (1)  Interface to packet networks and implement the functions
        required by that network.  These functions typically include:

        *  Encapsulating and decapsulating the IP datagrams with the
           connected network framing (e.g., an Ethernet header and
           checksum),

        *  Sending and receiving IP datagrams up to the maximum size
           supported by that network (this size is the network's Maximum
           Transmission Unit or MTU),

        *  Translating the IP destination address into an appropriate
           network-level address for the connected network (e.g., an
           Ethernet hardware address), if needed, and

        *  Responding to network flow control and error indications, if
           any.

   (2)  Conform to specific Internet protocols including the Internet
        Protocol (IPv4 and/or IPv6), Internet Control Message Protocol
        (ICMP), and others as necessary.

   (3)  Receive and forward Internet datagrams.  Important issues in
        this process are buffer management, congestion control, and
        fairness.

        *  Recognize error conditions and generate ICMP error and
           information messages as required.

        *  Drop datagrams whose time-to-live fields have reached zero.

        *  Fragment datagrams when necessary to fit into the MTU of the
           next link or interface.

   (4)  Choose a next-hop destination for each IP datagram, based on the
        information in its routing database.

   (5)  Usually support an interior gateway protocol (IGP) to carry out
        distributed routing and reachability algorithms with the other
        routers in the same autonomous system.  In addition, some
        routers will need to support an exterior gateway protocol (EGP)
        to exchange topological information with other autonomous
        systems.  For all routers, it is essential to provide the
        ability to manage static routing items.

   (6)  Provide network management and system support facilities,
        including loading, debugging, status reporting, statistics
        query, exception reporting, and control.



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   The classical IP router utilizing the ForCES framework constitutes a
   CE running some controlling IGP and/or EGP function or static route
   setup and FEs implemented by use of Logical Function Blocks (LFBs)
   conforming to the FE model [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>] specification.  The CE, in
   conformance to the ForCES protocol [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>] and the FE model
   [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>] specifications, instructs the LFBs on the FE how to treat
   received/sent packets.

   Packets in an IP router are received and transmitted on physical
   media typically referred to as "ports".  Different physical media
   will have different ways for encapsulating outgoing frames and
   decapsulating incoming frames.  The different physical media will
   also have different attributes that influence its behavior and how
   frames get encapsulated or decapsulated.  This document will only
   deal with Ethernet physical media.  Future documents may deal with
   other types of media.  This document will also interchangeably refer
   to a port as an abstraction that constitutes a physical layer (PHY)
   and a Media Access Control (MAC) layer, as described by LFBs like
   EtherPHYCop, EtherMACIn, and EtherMACOut.

   IP packets emanating from port LFBs are then processed by a
   validation LFB before being further forwarded to the next LFB.  After
   the validation process, the packet is passed to an LFB where an IP
   forwarding decision is made.  In the IP Forwarding LFBs, a Longest
   Prefix Match LFB is used to look up the destination information in a
   packet and select a next-hop index for sending the packet onward.  A
   next-hop LFB uses the next-hop index metadata to apply the proper
   headers to the IP packets and direct them to the proper egress.  Note
   that in the process of IP packet processing, in this document, we are
   adhering to the weak-host model [<a href="./rfc1122" title="&quot;Requirements for Internet Hosts - Communication Layers&quot;">RFC1122</a>] since that is the most
   usable model for a packet processing a Network Element.

<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>.  Overview of LFB Classes in the Library</span>

   It is critical to classify functional requirements into various
   classes of LFBs and construct a typical but also flexible enough base
   LFB library for various IP forwarding equipments.

<span class="h4"><a class="selflink" id="section-3.2.1" href="#section-3.2.1">3.2.1</a>.  LFB Design Choices</span>

   A few design principles were factored into choosing what the base
   LFBs look like:

   o  If a function can be designed by either one LFB or two or more
      LFBs with the same cost, the choice is to go with two or more LFBs
      so as to provide more flexibility for implementers.





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   o  An LFB should take advantage of its independence as much as
      possible and have minimal coupling with other LFBs.  The coupling
      may be from LFB attributes definitions as well as physical
      implementations.

   o  Unless there is a clear difference in functionality, similar
      packet processing in the base LFB library should not be
      represented simultaneously as two or more LFBs.  For instance, it
      should not be simultaneously defined with two different LFBs for
      the same next-hop processing.  Otherwise, it may add extra burden
      on implementation to achieve interoperability.

<span class="h4"><a class="selflink" id="section-3.2.2" href="#section-3.2.2">3.2.2</a>.  LFB Class Groupings</span>

   This document defines groups of LFBs for typical router function
   requirements:

   (1)  A group of Ethernet-processing LFBs are defined to abstract the
        packet processing for Ethernet as the port media type.  As
        Ethernet is the most popular media type with rich processing
        features, Ethernet media processing LFBs were a natural choice.
        Definitions for processing of other port media types like Packet
        over SONET (POS) or Asynchronous Transfer Mode (ATM) may be
        incorporated in the library in future versions of this document
        or in a separate document.  The following LFBs are defined for
        Ethernet processing:

        *  EtherPHYCop (<a href="#section-5.1.1">Section 5.1.1</a>)

        *  EtherMACIn (<a href="#section-5.1.2">Section 5.1.2</a>)

        *  EtherClassifier (<a href="#section-5.1.3">Section 5.1.3</a>)

        *  EtherEncap (<a href="#section-5.1.4">Section 5.1.4</a>)

        *  EtherMACOut (<a href="#section-5.1.5">Section 5.1.5</a>)

   (2)  A group of LFBs are defined for IP packet validation process.
        The following LFBs are defined for IP validation processing:

        *  IPv4Validator (<a href="#section-5.2.1">Section 5.2.1</a>)

        *  IPv6Validator (<a href="#section-5.2.2">Section 5.2.2</a>)

   (3)  A group of LFBs are defined to abstract IP forwarding process.
        The following LFBs are defined for IP forwarding processing:

        *  IPv4UcastLPM (<a href="#section-5.3.1">Section 5.3.1</a>)



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        *  IPv4NextHop (<a href="#section-5.3.2">Section 5.3.2</a>)

        *  IPv6UcastLPM (<a href="#section-5.3.3">Section 5.3.3</a>)

        *  IPv6NextHop (<a href="#section-5.3.4">Section 5.3.4</a>)

   (4)  A group of LFBs are defined to abstract the process for redirect
        operation, i.e., data packet transmission between CE and FEs.
        The following LFBs are defined for redirect processing:

        *  RedirectIn (<a href="#section-5.4.1">Section 5.4.1</a>)

        *  RedirectOut (<a href="#section-5.4.2">Section 5.4.2</a>)

   (5)  A group of LFBs are defined for abstracting some general purpose
        packet processing.  These processing processes are usually
        general to many processing locations in an FE LFB topology.  The
        following LFBs are defined for redirect processing:

        *  BasicMetadataDispatch (<a href="#section-5.5.1">Section 5.5.1</a>)

        *  GenericScheduler (<a href="#section-5.5.2">Section 5.5.2</a>)

<span class="h4"><a class="selflink" id="section-3.2.3" href="#section-3.2.3">3.2.3</a>.  Sample LFB Class Application</span>

   Although <a href="#section-7">Section 7</a> will present use cases for the LFBs defined in
   this document, this section shows a simple sample LFB class
   application in advance so that readers can get a quick overlook of
   the LFB classes with the usage.

   Figure 1 shows a simple LFB processing path for Ethernet packets
   entered from Ethernet physical ports.

   +-----+                +------+
   |     |EtherPHYIn      |      |            from some LFB(s) that
   |     |&lt;---------------|Ether |&lt;---------- generate Ethernet
   |     |                |MACOut|            packets
   |     |                | LFB  |
   |Ether|                +------+
   |PHY  |                +------+
   |Cop  |                |      |
   |LFB  |EtherPHYOut     | Ether|            to some LFB(s) that
   |     |---------------&gt;| MACIn|----------&gt; may classify Ethernet
   |     |                |  LFB |            packets and do IP-layer
   |     |                |      |            processing
   +-----+                +------+

                  Figure 1:  A Simple Sample LFB Use Case



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   In the figure, Ethernet packets from outer networks enter via the
   EtherPHYCop LFB (<a href="#section-5.1.1">Section 5.1.1</a>), which describes Ethernet copper
   interface properties (like the link speed) at the physical layer.
   After physical-layer processing, Ethernet packets are delivered to
   the EtherMACIn LFB (<a href="#section-5.1.2">Section 5.1.2</a>) to describe its MAC-layer
   processing functions (like locality check).  The packets after the
   EtherMACIn LFB may require further processing to implement various
   functions (like IP-layer forwarding); therefore, some LFBs may follow
   the EtherMACIn LFB in topology to describe followed processing
   functions.

   Meanwhile, packets generated by some LFB(s) may need to be submitted
   to outer physical networks.  The process is described in the figure
   by an EtherMACOut LFB (<a href="#section-5.1.5">Section 5.1.5</a>) at the MAC layer and the
   EtherPHYCop LFB at the physical layer.

<span class="h3"><a class="selflink" id="section-3.3" href="#section-3.3">3.3</a>.  Document Structure</span>

   Base type definitions, including data types, packet frame types, and
   metadata types, are presented in advance for definitions of various
   LFB classes.  <a href="#section-4">Section 4</a> ("Base Types") provides a description on the
   base types used by this LFB library.  To enable extensive use of
   these base types by other LFB class definitions, the base type
   definitions are provided as a separate library.

   Within every group of LFB classes, a set of LFBs are defined for
   individual function purposes.  <a href="#section-5">Section 5</a> ("LFB Class Descriptions")
   provides text descriptions on the individual LFBs.  Note that for a
   complete definition of an LFB, a text description and an XML
   definition are required.

   LFB classes are finally defined by XML with specifications and schema
   defined in the ForCES FE model [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>].  <a href="#section-6">Section 6</a> ("XML for LFB
   Library") provides the complete XML definitions of the base LFB
   classes library.

   <a href="#section-7">Section 7</a> provides several use cases on how some typical router
   functions can be implemented using the base LFB library defined in
   this document.

<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>.  Base Types</span>

   The FE model [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>] has specified predefined (built-in) atomic
   data types: char, uchar, int16, uint16, int32, uint32, int64, uint64,
   string[N], string, byte[N], boolean, octetstring[N], float16,
   float32, and float64.





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   Note that, unlike the Simple Network Management Protocol (SNMP)
   information model, called the Structure of Management Information
   (SMI) [<a href="./rfc2578" title="&quot;Structure of Management Information Version 2 (SMIv2)&quot;">RFC2578</a>], the FE model has not defined specific atomic data
   types for counting purposes.  This document also does not define
   specific counter types.  To describe LFB elements for packet
   statistics, which actually requires counters on packets, an unsigned
   integer, like an uint32 or an uint64, is adopted.  This document
   states that any LFB element defined for counting purposes is
   specified to monotonically increase until it reaches a maximum value,
   when it wraps around and starts increasing again from zero.  This
   document also states that how the unsigned integer element might be
   maintained to cope with issues like counter discontinuities when a
   counter wraps or is reset for any reason is an implementation's
   issue.  If a CE is expected to understand more meanings of the
   counter element than stated above, a private definition on the
   element between the CE and FE may be required.

   Based on the atomic data types and with the use of type definition
   elements in the FE model XML schema, new data types, packet frame
   types, and metadata types can be defined.

   To define a base LFB library for typical router functions, a set of
   base data types, frame types, and metadata types should be defined.
   This section provides a brief description of the base types and a
   full XML definition of them as well.

   The base type XML definitions are provided with a separate XML
   library file named "BaseTypeLibrary".  Users can refer to this
   library by the statement:

   &lt;load library="BaseTypeLibrary" location="..."/&gt;




















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<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>.  Data Types</span>

   Data types defined in the base type library are categorized by the
   following types: atomic, compound struct, and compound array.

<span class="h4"><a class="selflink" id="section-4.1.1" href="#section-4.1.1">4.1.1</a>.  Atomic</span>

   The following data types are defined as atomic data types and put in
   the base type library:

    Data Type Name      Brief Description
    --------------      -----------------
    IPv4Addr            IPv4 address
    IPv6Addr            IPv6 address
    IEEEMAC             IEEE MAC address
    LANSpeedType        LAN speed by value types
    DuplexType          Duplex types
    PortStatusType      The possible types of port status, used for
                         both administrative and operative status
    VlanIDType          The type of VLAN ID
    VlanPriorityType    The type of VLAN priority
    SchdDisciplineType  Scheduling discipline type

<span class="h4"><a class="selflink" id="section-4.1.2" href="#section-4.1.2">4.1.2</a>.  Compound Struct</span>

   The following compound struct types are defined in the base type
   library:

    Data Type Name           Brief Description
    --------------           -----------------
    EtherDispatchEntryType   Entry type for Ethernet dispatch table
    VlanInputTableEntryType  Entry type for VLAN input table
    EncapTableEntryType      Entry type for Ethernet encapsulation table
    MACInStatsType           Statistics type for EtherMACIn LFB
    MACOutStatsType          Statistics type for EtherMACOut LFB
    EtherClassifyStatsType   Entry type for statistics table in
                              EtherClassifier LFB
    IPv4PrefixInfoType       Entry type for IPv4 prefix table
    IPv6PrefixInfoType       Entry type for IPv6 prefix table
    IPv4NextHopInfoType      Entry type for IPv4 next-hop table
    IPv6NextHopInfoType      Entry type for IPv6 next-hop table
    IPv4ValidatorStatsType   Statistics type in IPv4validator LFB
    IPv6ValidatorStatsType   Statistics type in IPv6validator LFB
    IPv4UcastLPMStatsType    Statistics type in IPv4UcastLPM LFB
    IPv6UcastLPMStatsType    Statistics type in IPv6UcastLPM LFB
    QueueStatsType           Entry type for queue depth table
    MetadataDispatchType     Entry type for metadata dispatch table




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<span class="h4"><a class="selflink" id="section-4.1.3" href="#section-4.1.3">4.1.3</a>.  Compound Array</span>

   Compound array types are mostly created based on compound struct
   types for LFB table components.  The following compound array types
   are defined in this base type library:

    Data Type Name               Brief Description
    --------------               -----------------
    EtherClassifyStatsTableType  Type for Ethernet classifier statistics
                                  information table
    EtherDispatchTableType       Type for Ethernet dispatch table
    VlanInputTableType           Type for VLAN input table
    EncapTableType               Type for Ethernet encapsulation table
    IPv4PrefixTableType          Type for IPv4 prefix table
    IPv6PrefixTableType          Type for IPv6 prefix table
    IPv4NextHopTableType         Type for IPv4 next-hop table
    IPv6NextHopTableType         Type for IPv6 next-hop table
    MetadataDispatchTableType    Type for Metadata dispatch table
    QueueStatsTableType          Type for Queue depth table

<span class="h3"><a class="selflink" id="section-4.2" href="#section-4.2">4.2</a>.  Frame Types</span>

   According to the FE model [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>], frame types are used in LFB
   definitions to define packet frame types that an LFB expects at its
   input port and that the LFB emits at its output port.  The &lt;frameDef&gt;
   element in the FE model is used to define a new frame type.

   The following frame types are defined in the base type library:

    Frame Name           Brief Description
    --------------       -----------------
    EthernetII           An Ethernet II frame
    ARP                  An ARP packet frame
    IPv4                 An IPv4 packet frame
    IPv6                 An IPv6 packet frame
    IPv4Unicast          An IPv4 unicast packet frame
    IPv4Multicast        An IPv4 multicast packet frame
    IPv6Unicast          An IPv6 unicast packet frame
    IPv6Multicast        An IPv6 multicast packet frame
    Arbitrary            Any type of packet frames











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<span class="h3"><a class="selflink" id="section-4.3" href="#section-4.3">4.3</a>.  Metadata Types</span>

   LFB metadata is used to communicate per-packet state from one LFB to
   another.  The &lt;metadataDef&gt; element in the FE model is used to define
   a new metadata type.

   The following metadata types are currently defined in the base type
   library.

   Metadata Name  Metadata ID  Brief Description
   ------------   -----------  -----------------
   PHYPortID          1        Metadata indicating a physical port ID
   SrcMAC             2        Metadata indicating a source MAC address
   DstMAC             3        Metadata indicating a destination MAC
                                address
   LogicalPortID      4        Metadata of a logical port ID
   EtherType          5        Metadata indicating an Ethernet type
   VlanID             6        Metadata of a VLAN ID
   VlanPriority       7        Metadata of a VLAN priority
   NextHopIPv4Addr    8        Metadata representing a next-hop IPv4
                                address
   NextHopIPv6Addr    9        Metadata representing a next-hop IPv6
                                address
   HopSelector        10       Metadata indicating a hop selector
   ExceptionID        11       Metadata indicating exception types for
                                exceptional cases during LFB processing
   ValidateErrorID    12       Metadata indicating error types when a
                                packet passes validation process
   L3PortID           13       Metadata indicating ID of an L3 logical
                                port
   RedirectIndex      14       Metadata that CE sends to RedirectIn LFB,
                                indicating an associated packet a group
                                output port index of the LFB
   MediaEncapInfoIndex 15      A search key a packet uses to look up a
                                table in related LFBs to select an
                                encapsulation media















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<span class="h3"><a class="selflink" id="section-4.4" href="#section-4.4">4.4</a>.  XML for Base Type Library</span>

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;LFBLibrary xmlns="urn:ietf:params:xml:ns:forces:lfbmodel:1.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     provides="BaseTypeLibrary"&gt;
   &lt;frameDefs&gt;
      &lt;frameDef&gt;
         &lt;name&gt;EthernetAll&lt;/name&gt;
         &lt;synopsis&gt;Packet with any Ethernet type&lt;/synopsis&gt;
      &lt;/frameDef&gt;
      &lt;frameDef&gt;
         &lt;name&gt;EthernetII&lt;/name&gt;
         &lt;synopsis&gt;Packet with Ethernet II type&lt;/synopsis&gt;
      &lt;/frameDef&gt;
      &lt;frameDef&gt;
         &lt;name&gt;ARP&lt;/name&gt;
         &lt;synopsis&gt;ARP packet&lt;/synopsis&gt;
      &lt;/frameDef&gt;
      &lt;frameDef&gt;
         &lt;name&gt;IPv4&lt;/name&gt;
         &lt;synopsis&gt;IPv4 packet&lt;/synopsis&gt;
      &lt;/frameDef&gt;
      &lt;frameDef&gt;
         &lt;name&gt;IPv6&lt;/name&gt;
         &lt;synopsis&gt;IPv6 packet&lt;/synopsis&gt;
      &lt;/frameDef&gt;
      &lt;frameDef&gt;
         &lt;name&gt;IPv4Unicast&lt;/name&gt;
         &lt;synopsis&gt;IPv4 unicast packet&lt;/synopsis&gt;
      &lt;/frameDef&gt;
      &lt;frameDef&gt;
         &lt;name&gt;IPv4Multicast&lt;/name&gt;
         &lt;synopsis&gt;IPv4 multicast packet&lt;/synopsis&gt;
      &lt;/frameDef&gt;
      &lt;frameDef&gt;
         &lt;name&gt;IPv6Unicast&lt;/name&gt;
         &lt;synopsis&gt;IPv6 unicast packet&lt;/synopsis&gt;
      &lt;/frameDef&gt;
      &lt;frameDef&gt;
         &lt;name&gt;IPv6Multicast&lt;/name&gt;
         &lt;synopsis&gt;IPv6 multicast packet&lt;/synopsis&gt;
      &lt;/frameDef&gt;
      &lt;frameDef&gt;
         &lt;name&gt;Arbitrary&lt;/name&gt;
         &lt;synopsis&gt;Any type of packet&lt;/synopsis&gt;
      &lt;/frameDef&gt;
   &lt;/frameDefs&gt;



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   &lt;dataTypeDefs&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv4Addr&lt;/name&gt;
         &lt;synopsis&gt;IPv4 address&lt;/synopsis&gt;
         &lt;typeRef&gt;byte[4]&lt;/typeRef&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv6Addr&lt;/name&gt;
         &lt;synopsis&gt;IPv6 address&lt;/synopsis&gt;
         &lt;typeRef&gt;byte[16]&lt;/typeRef&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IEEEMAC&lt;/name&gt;
         &lt;synopsis&gt;IEEE MAC address&lt;/synopsis&gt;
         &lt;typeRef&gt;byte[6]&lt;/typeRef&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
        &lt;name&gt;LANSpeedType&lt;/name&gt;
        &lt;synopsis&gt;LAN speed type&lt;/synopsis&gt;
        &lt;atomic&gt;
         &lt;baseType&gt;uint32&lt;/baseType&gt;
         &lt;specialValues&gt;
           &lt;specialValue value="0x00000000"&gt;
            &lt;name&gt;LAN_SPEED_NONE&lt;/name&gt;
            &lt;synopsis&gt;Nothing connected&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000001"&gt;
            &lt;name&gt;LAN_SPEED_10M&lt;/name&gt;
            &lt;synopsis&gt;10M Ethernet&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000002"&gt;
            &lt;name&gt;LAN_SPEED_100M&lt;/name&gt;
            &lt;synopsis&gt;100M Ethernet&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000003"&gt;
            &lt;name&gt;LAN_SPEED_1G&lt;/name&gt;
            &lt;synopsis&gt;1G Ethernet&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000004"&gt;
            &lt;name&gt;LAN_SPEED_10G&lt;/name&gt;
            &lt;synopsis&gt;10G Ethernet&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000005"&gt;
            &lt;name&gt;LAN_SPEED_40G&lt;/name&gt;
            &lt;synopsis&gt;40G Ethernet&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000006"&gt;
            &lt;name&gt;LAN_SPEED_100G&lt;/name&gt;



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            &lt;synopsis&gt;100G Ethernet&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000007"&gt;
            &lt;name&gt;LAN_SPEED_400G&lt;/name&gt;
            &lt;synopsis&gt;400G Ethernet&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000008"&gt;
            &lt;name&gt;LAN_SPEED_1T&lt;/name&gt;
            &lt;synopsis&gt;1T Ethernet&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000009"&gt;
            &lt;name&gt;LAN_SPEED_OTHER&lt;/name&gt;
            &lt;synopsis&gt;Other LAN speed type&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x0000000A"&gt;
            &lt;name&gt;LAN_SPEED_AUTO&lt;/name&gt;
            &lt;synopsis&gt;LAN speed by auto negotiation&lt;/synopsis&gt;
           &lt;/specialValue&gt;
         &lt;/specialValues&gt;
        &lt;/atomic&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
        &lt;name&gt;DuplexType&lt;/name&gt;
        &lt;synopsis&gt;Duplex mode type&lt;/synopsis&gt;
        &lt;atomic&gt;
         &lt;baseType&gt;uint32&lt;/baseType&gt;
         &lt;specialValues&gt;
           &lt;specialValue value="0x00000001"&gt;
            &lt;name&gt;Auto&lt;/name&gt;
            &lt;synopsis&gt;Auto negotiation&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000002"&gt;
            &lt;name&gt;HalfDuplex&lt;/name&gt;
            &lt;synopsis&gt;Half duplex&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="0x00000003"&gt;
            &lt;name&gt;FullDuplex&lt;/name&gt;
            &lt;synopsis&gt;Full duplex&lt;/synopsis&gt;
           &lt;/specialValue&gt;
         &lt;/specialValues&gt;
        &lt;/atomic&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
        &lt;name&gt;PortStatusType&lt;/name&gt;
        &lt;synopsis&gt;
          Type for port status, used for both administrative and
          operative status.
        &lt;/synopsis&gt;



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        &lt;atomic&gt;
         &lt;baseType&gt;uchar&lt;/baseType&gt;
         &lt;specialValues&gt;
           &lt;specialValue value="0"&gt;
            &lt;name&gt;Disabled&lt;/name&gt;
            &lt;synopsis&gt;Port disabled&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="1"&gt;
            &lt;name&gt;Up&lt;/name&gt;
            &lt;synopsis&gt;Port up&lt;/synopsis&gt;
           &lt;/specialValue&gt;
           &lt;specialValue value="2"&gt;
            &lt;name&gt;Down&lt;/name&gt;
            &lt;synopsis&gt;Port down&lt;/synopsis&gt;
           &lt;/specialValue&gt;
         &lt;/specialValues&gt;
        &lt;/atomic&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;MACInStatsType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type defined for statistics in EtherMACIn LFB.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;NumPacketsReceived&lt;/name&gt;
               &lt;synopsis&gt;Number of packets received&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;NumPacketsDropped&lt;/name&gt;
               &lt;synopsis&gt;Number of packets dropped&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;MACOutStatsType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type defined for statistics in EtherMACOut LFB.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;NumPacketsTransmitted&lt;/name&gt;
               &lt;synopsis&gt;Number of packets transmitted&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;



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               &lt;name&gt;NumPacketsDropped&lt;/name&gt;
               &lt;synopsis&gt;Number of packets dropped&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;EtherDispatchEntryType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type defined for entry of Ethernet dispatch
           table in EtherClassifier LFB.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;LogicalPortID&lt;/name&gt;
               &lt;synopsis&gt;Logical port ID&lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;EtherType&lt;/name&gt;
               &lt;synopsis&gt;
                The Ethernet type of the Ethernet packet.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint16&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;Reserved&lt;/name&gt;
               &lt;synopsis&gt;
               A reserved bit space mainly for purpose of padding
               and packing efficiency.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint16&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="4"&gt;
               &lt;name&gt;LFBOutputSelectIndex&lt;/name&gt;
                &lt;synopsis&gt;
                  Index for a packet to select an instance in the
                  group output port of EtherClassifier LFB to output.
                &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;







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         &lt;name&gt;EtherDispatchTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type defined for Ethernet dispatch table in
           EtherClassifier LFB.  The table is composed of an array
           of entries with EtherDispatchEntryType data type.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;EtherDispatchEntryType&lt;/typeRef&gt;
         &lt;/array&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;VlanIDType&lt;/name&gt;
         &lt;synopsis&gt;Data type for VLAN ID&lt;/synopsis&gt;
         &lt;atomic&gt;
         &lt;baseType&gt;uint16&lt;/baseType&gt;
           &lt;rangeRestriction&gt;
              &lt;allowedRange min="0" max="4095"/&gt;
            &lt;/rangeRestriction&gt;
         &lt;/atomic&gt;
       &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;VlanPriorityType&lt;/name&gt;
         &lt;synopsis&gt;Data type for VLAN priority&lt;/synopsis&gt;
         &lt;atomic&gt;
         &lt;baseType&gt;uchar&lt;/baseType&gt;
           &lt;rangeRestriction&gt;
              &lt;allowedRange min="0" max="7"/&gt;
           &lt;/rangeRestriction&gt;
         &lt;/atomic&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;VlanInputTableEntryType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for entry of VLAN input table in EtherClassifier
           LFB.  Each entry of the table contains an incoming port ID,
           a VLAN ID and a logical port ID.  Every input packet is
           assigned with a new logical port ID according to the
           packet incoming port ID and the VLAN ID.
           &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;IncomingPortID&lt;/name&gt;
               &lt;synopsis&gt;The incoming port ID&lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;VlanID&lt;/name&gt;
               &lt;synopsis&gt;The VLAN ID&lt;/synopsis&gt;



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               &lt;typeRef&gt;VlanIDType&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;Reserved&lt;/name&gt;
               &lt;synopsis&gt;
               A reserved bit space mainly for purpose of padding
               and packing efficiency.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint16&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="4"&gt;
               &lt;name&gt;LogicalPortID&lt;/name&gt;
               &lt;synopsis&gt;The logical port ID&lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;VlanInputTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for the VLAN input table in EtherClassifier
           LFB.  The table is composed of an array of entries with
           VlanInputTableEntryType.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;VlanInputTableEntryType&lt;/typeRef&gt;
         &lt;/array&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;EtherClassifyStatsType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for entry of statistics table in EtherClassifier
           LFB.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;EtherType&lt;/name&gt;
               &lt;synopsis&gt;
                The Ethernet type of the Ethernet packet.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint16&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;Reserved&lt;/name&gt;
               &lt;synopsis&gt;
               A reserved bit space mainly for purpose of padding
               and packing efficiency.
               &lt;/synopsis&gt;



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               &lt;typeRef&gt;uint16&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;PacketsNum&lt;/name&gt;
               &lt;synopsis&gt;Packets number&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;EtherClassifyStatsTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for statistics table in EtherClassifier LFB.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;EtherClassifyStatsType&lt;/typeRef&gt;
         &lt;/array&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv4ValidatorStatsType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for statistics in IPv4validator LFB.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;badHeaderPkts&lt;/name&gt;
               &lt;synopsis&gt;Number of packets with bad header&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;badTotalLengthPkts&lt;/name&gt;
               &lt;synopsis&gt;
                 Number of packets with bad total length
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;badTTLPkts&lt;/name&gt;
               &lt;synopsis&gt;Number of packets with bad TTL&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="4"&gt;
               &lt;name&gt;badChecksumPkts&lt;/name&gt;
               &lt;synopsis&gt;Number of packets with bad checksum&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;



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      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv6ValidatorStatsType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for statistics in IPv6validator LFB.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;badHeaderPkts&lt;/name&gt;
               &lt;synopsis&gt;Number of packets with bad header&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;badTotalLengthPkts&lt;/name&gt;
               &lt;synopsis&gt;
               Number of packets with bad total length.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;badHopLimitPkts&lt;/name&gt;
               &lt;synopsis&gt;
               Number of packets with bad hop limit.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv4PrefixInfoType&lt;/name&gt;
         &lt;synopsis&gt;Data type for entry of IPv4 longest prefix match
          table in IPv4UcastLPM LFB.  The destination IPv4 address
          of every input packet is used as a search key to look up
          the table to find out a next-hop selector.&lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;IPv4Address&lt;/name&gt;
               &lt;synopsis&gt;The destination IPv4 address&lt;/synopsis&gt;
               &lt;typeRef&gt;IPv4Addr&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;Prefixlen&lt;/name&gt;
               &lt;synopsis&gt;The prefix length&lt;/synopsis&gt;
               &lt;atomic&gt;
                  &lt;baseType&gt;uchar&lt;/baseType&gt;
                  &lt;rangeRestriction&gt;
                     &lt;allowedRange min="0" max="32"/&gt;
                  &lt;/rangeRestriction&gt;
               &lt;/atomic&gt;



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            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;ECMPFlag&lt;/name&gt;
               &lt;synopsis&gt;The ECMP flag&lt;/synopsis&gt;
               &lt;atomic&gt;
                  &lt;baseType&gt;boolean&lt;/baseType&gt;
                  &lt;specialValues&gt;
                     &lt;specialValue value="false"&gt;
                        &lt;name&gt;False&lt;/name&gt;
                        &lt;synopsis&gt;
                         ECMP false, indicating the route
                         does not have multiple next hops.
                        &lt;/synopsis&gt;
                     &lt;/specialValue&gt;
                     &lt;specialValue value="true"&gt;
                        &lt;name&gt;True&lt;/name&gt;
                        &lt;synopsis&gt;
                          ECMP true, indicating the route
                          has multiple next hops.
                        &lt;/synopsis&gt;
                     &lt;/specialValue&gt;
                  &lt;/specialValues&gt;
               &lt;/atomic&gt;
            &lt;/component&gt;
            &lt;component componentID="4"&gt;
               &lt;name&gt;DefaultRouteFlag&lt;/name&gt;
               &lt;synopsis&gt;Default route flag&lt;/synopsis&gt;
               &lt;atomic&gt;
                  &lt;baseType&gt;boolean&lt;/baseType&gt;
                  &lt;specialValues&gt;
                     &lt;specialValue value="false"&gt;
                        &lt;name&gt;False&lt;/name&gt;
                        &lt;synopsis&gt;
                          Default route false, indicating the
                          route is not a default route.
                        &lt;/synopsis&gt;
                     &lt;/specialValue&gt;
                     &lt;specialValue value="true"&gt;
                        &lt;name&gt;True&lt;/name&gt;
                        &lt;synopsis&gt;
                          Default route true, indicating the
                          route is a default route.
                        &lt;/synopsis&gt;
                     &lt;/specialValue&gt;
                  &lt;/specialValues&gt;
               &lt;/atomic&gt;
            &lt;/component&gt;
            &lt;component componentID="5"&gt;



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               &lt;name&gt;Reserved&lt;/name&gt;
               &lt;synopsis&gt;
               A reserved bit space mainly for purpose of padding
               and packing efficiency.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uchar&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="6"&gt;
               &lt;name&gt;HopSelector&lt;/name&gt;
               &lt;synopsis&gt;
                 The HopSelector produced by the prefix matching LFB,
                 which will be output to downstream LFB to find next-
                 hop information.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv4PrefixTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for IPv4 longest prefix match table in
           IPv4UcastLPM LFB.  Entry of the table is
           of IPv4PrefixInfoType data type.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;IPv4PrefixInfoType&lt;/typeRef&gt;
         &lt;/array&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv4UcastLPMStatsType&lt;/name&gt;
         &lt;synopsis&gt;
          Data type for statistics in IPv4UcastLPM LFB.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;InRcvdPkts&lt;/name&gt;
               &lt;synopsis&gt;Number of received input packets.&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;FwdPkts&lt;/name&gt;
               &lt;synopsis&gt;Number of forwarded packets.&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;





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               &lt;name&gt;NoRoutePkts&lt;/name&gt;
               &lt;synopsis&gt;
                Number of packets with no route found.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv6PrefixInfoType&lt;/name&gt;
         &lt;synopsis&gt;Data type for entry of IPv6 longest prefix match
          table in IPv6UcastLPM LFB.  The destination IPv6 address
          of every input packet is used as a search key to look up
          the table to find out a next-hop selector.&lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;IPv6Address&lt;/name&gt;
               &lt;synopsis&gt;The destination IPv6 address&lt;/synopsis&gt;
               &lt;typeRef&gt;IPv6Addr&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;Prefixlen&lt;/name&gt;
               &lt;synopsis&gt;The prefix length&lt;/synopsis&gt;
               &lt;atomic&gt;
                  &lt;baseType&gt;uchar&lt;/baseType&gt;
                  &lt;rangeRestriction&gt;
                     &lt;allowedRange min="0" max="128"/&gt;
                  &lt;/rangeRestriction&gt;
               &lt;/atomic&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;ECMPFlag&lt;/name&gt;
               &lt;synopsis&gt;ECMP flag&lt;/synopsis&gt;
               &lt;atomic&gt;
                  &lt;baseType&gt;boolean&lt;/baseType&gt;
                  &lt;specialValues&gt;
                     &lt;specialValue value="false"&gt;
                        &lt;name&gt;False&lt;/name&gt;
                        &lt;synopsis&gt;ECMP false&lt;/synopsis&gt;
                     &lt;/specialValue&gt;
                     &lt;specialValue value="true"&gt;
                        &lt;name&gt;True&lt;/name&gt;
                        &lt;synopsis&gt;ECMP true&lt;/synopsis&gt;
                     &lt;/specialValue&gt;
                  &lt;/specialValues&gt;
               &lt;/atomic&gt;
            &lt;/component&gt;
            &lt;component componentID="4"&gt;



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               &lt;name&gt;DefaultRouteFlag&lt;/name&gt;
               &lt;synopsis&gt;Default route flag&lt;/synopsis&gt;
               &lt;atomic&gt;
                  &lt;baseType&gt;boolean&lt;/baseType&gt;
                  &lt;specialValues&gt;
                     &lt;specialValue value="false"&gt;
                        &lt;name&gt;False&lt;/name&gt;
                        &lt;synopsis&gt;Default false&lt;/synopsis&gt;
                     &lt;/specialValue&gt;
                     &lt;specialValue value="true"&gt;
                        &lt;name&gt;True&lt;/name&gt;
                        &lt;synopsis&gt;Default route true&lt;/synopsis&gt;
                     &lt;/specialValue&gt;
                  &lt;/specialValues&gt;
               &lt;/atomic&gt;
            &lt;/component&gt;
            &lt;component componentID="5"&gt;
               &lt;name&gt;Reserved&lt;/name&gt;
               &lt;synopsis&gt;
               A reserved bit space mainly for purpose of padding
               and packing efficiency.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uchar&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="6"&gt;
               &lt;name&gt;HopSelector&lt;/name&gt;
               &lt;synopsis&gt;
                 The HopSelector produced by the prefix matching LFB,
                 which will be output to downstream LFB to find next-
                 hop information.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv6PrefixTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for IPv6 longest prefix match table in
           IPv6UcastLPM LFB.  Entry of the table is
           of IPv6PrefixInfoType data type.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;IPv6PrefixInfoType&lt;/typeRef&gt;
         &lt;/array&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;




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         &lt;name&gt;IPv6UcastLPMStatsType&lt;/name&gt;
         &lt;synopsis&gt;Data type for statistics in IPv6UcastLPM LFB
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;InRcvdPkts&lt;/name&gt;
               &lt;synopsis&gt;Number of received input packets&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;FwdPkts&lt;/name&gt;
               &lt;synopsis&gt;Number of forwarded packets&lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;NoRoutePkts&lt;/name&gt;
               &lt;synopsis&gt;
                Number of packets with no route found.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv4NextHopInfoType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for entry of IPv4 next-hop information table
           in IPv4NextHop LFB.  The table uses a hop selector
           received from upstream LFB as a search key to look up
           index of the table to find the next-hop information.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;L3PortID&lt;/name&gt;
               &lt;synopsis&gt;
                The ID of the logical output port that is to pass
                onto downstream LFB, indicating what port to the
                neighbor is as defined by L3.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;MTU&lt;/name&gt;
               &lt;synopsis&gt;
                Maximum Transmission Unit for outgoing port
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;



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            &lt;component componentID="3"&gt;
               &lt;name&gt;NextHopIPAddr&lt;/name&gt;
               &lt;synopsis&gt;The next-hop IPv4 address&lt;/synopsis&gt;
               &lt;typeRef&gt;IPv4Addr&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="4"&gt;
               &lt;name&gt;MediaEncapInfoIndex&lt;/name&gt;
               &lt;synopsis&gt;
                 The index passed onto a downstream encapsulation
                 LFB, used there as a search key to lookup further
                 encapsulation information.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="5"&gt;
               &lt;name&gt;LFBOutputSelectIndex&lt;/name&gt;
                &lt;synopsis&gt;
                  The index for the IPv4NextHop LFB to choose an
                  instance in the group output port of the LFB to
                  output.
                &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv4NextHopTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for IPv4 next-hop table in IPv4NextHop LFB.
           Entry of the table is of IPv4NextHopInfoType data type.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;IPv4NextHopInfoType&lt;/typeRef&gt;
         &lt;/array&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv6NextHopInfoType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for entry of IPv6 next-hop information table
           in IPv6NextHop LFB.  The table uses a hop selector
           received from upstream LFB as a search key to look up
           index of the table to find the next-hop information.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;






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               &lt;name&gt;L3PortID&lt;/name&gt;
               &lt;synopsis&gt;
                The ID of the logical output port that is to pass
                onto downstream LFB, indicating what port to the
                neighbor is as defined by L3.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;MTU&lt;/name&gt;
               &lt;synopsis&gt;
                 Maximum Transmission Unit for outgoing port
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;NextHopIPAddr&lt;/name&gt;
               &lt;synopsis&gt;The next-hop IPv6 address&lt;/synopsis&gt;
               &lt;typeRef&gt;IPv6Addr&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="4"&gt;
               &lt;name&gt;MediaEncapInfoIndex&lt;/name&gt;
               &lt;synopsis&gt;
                 The index passed onto a downstream encapsulation
                 LFB, used there as a search key to lookup further
                 encapsulation information.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="5"&gt;
               &lt;name&gt;LFBOutputSelectIndex&lt;/name&gt;
                &lt;synopsis&gt;
                 The index for the IPv6NextHop LFB to choose an instance
                 in the group output port of the LFB to output.
                &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;IPv6NextHopTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for IPv6 next-hop table in IPv6NextHop LFB.
           Entry of the table is of IPv6NextHopInfoType data type.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;IPv6NextHopInfoType&lt;/typeRef&gt;
         &lt;/array&gt;



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      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;EncapTableEntryType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for entry of Ethernet encapsulation table in
           EtherEncap LFB.  The LFB uses the MediaEncapInfoIndex
           received from upstream LFB as index of the table to
           find encapsulation information of every packet.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;DstMac&lt;/name&gt;
               &lt;synopsis&gt;
                 Destination MAC address for Ethernet encapsulation of
                 the packet.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;IEEEMAC&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;SrcMac&lt;/name&gt;
               &lt;synopsis&gt;
                 Source MAC address for Ethernet encapsulation of the
                 packet.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;IEEEMAC&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;VlanID&lt;/name&gt;
               &lt;synopsis&gt;The VLAN ID assigned to the packet&lt;/synopsis&gt;
               &lt;typeRef&gt;VlanIDType&lt;/typeRef&gt;
            &lt;/component&gt;
             &lt;component componentID="4"&gt;
               &lt;name&gt;Reserved&lt;/name&gt;
               &lt;synopsis&gt;
                A reserved bit space mainly for purpose of padding
                and packing efficiency.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint16&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="5"&gt;
               &lt;name&gt;L2PortID&lt;/name&gt;
               &lt;synopsis&gt;
                 The L2 logical output port ID for the packet.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;



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      &lt;dataTypeDef&gt;
         &lt;name&gt;EncapTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for Ethernet encapsulation table in EtherEncap
           LFB.  Entry of the table is of EncapTableEntryType data
           type.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;EncapTableEntryType&lt;/typeRef&gt;
         &lt;/array&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;MetadataDispatchType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for entry of metadata dispatch table used in
           BasicMetadataDispatch LFB.  The LFB uses a metadata value
           as a search key to look up the table to find an index of
           the LFB group output port to output the packet.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;MetadataValue&lt;/name&gt;
               &lt;synopsis&gt;The value of the dispatch metadata&lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;OutputIndex&lt;/name&gt;
               &lt;synopsis&gt;
                 Index of a group output port for outgoing packets.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;MetadataDispatchTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for metadata dispatch table used in
           BasicMetadataDispatch LFB.  Metadata value of
           the table is also defined as a content key field.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;MetadataDispatchType&lt;/typeRef&gt;
           &lt;contentKey contentKeyID="1"&gt;
           &lt;contentKeyField&gt;MetadataValue&lt;/contentKeyField&gt;
           &lt;/contentKey&gt;
         &lt;/array&gt;
      &lt;/dataTypeDef&gt;



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      &lt;dataTypeDef&gt;
         &lt;name&gt;SchdDisciplineType&lt;/name&gt;
         &lt;synopsis&gt;Scheduling discipline type&lt;/synopsis&gt;
         &lt;atomic&gt;
            &lt;baseType&gt;uint32&lt;/baseType&gt;
            &lt;specialValues&gt;
               &lt;specialValue value="1"&gt;
                  &lt;name&gt;RR&lt;/name&gt;
                  &lt;synopsis&gt;
                    Round Robin scheduling discipline
                  &lt;/synopsis&gt;
               &lt;/specialValue&gt;
            &lt;/specialValues&gt;
         &lt;/atomic&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;QueueStatsType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for entry of queue statistics table in
           GenericScheduler LFB.
         &lt;/synopsis&gt;
         &lt;struct&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;QueueID&lt;/name&gt;
               &lt;synopsis&gt;The input queue ID&lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2"&gt;
               &lt;name&gt;QueueDepthInPackets&lt;/name&gt;
               &lt;synopsis&gt;Current queue depth in packets&lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3"&gt;
               &lt;name&gt;QueueDepthInBytes&lt;/name&gt;
               &lt;synopsis&gt;Current queue depth in bytes&lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/struct&gt;
      &lt;/dataTypeDef&gt;
      &lt;dataTypeDef&gt;
         &lt;name&gt;QueueStatsTableType&lt;/name&gt;
         &lt;synopsis&gt;
           Data type for queue statistics table in GenericScheduler
           LFB.  Entry of the table is of QueueStatsType data type.
         &lt;/synopsis&gt;
         &lt;array type="variable-size"&gt;
           &lt;typeRef&gt;QueueStatsType&lt;/typeRef&gt;
         &lt;/array&gt;



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      &lt;/dataTypeDef&gt;
   &lt;/dataTypeDefs&gt;
   &lt;metadataDefs&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;PHYPortID&lt;/name&gt;
         &lt;synopsis&gt;Metadata indicating physical port ID&lt;/synopsis&gt;
         &lt;metadataID&gt;1&lt;/metadataID&gt;
         &lt;typeRef&gt;uint32&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;SrcMAC&lt;/name&gt;
         &lt;synopsis&gt;Metadata indicating source MAC address&lt;/synopsis&gt;
         &lt;metadataID&gt;2&lt;/metadataID&gt;
         &lt;typeRef&gt;IEEEMAC&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;DstMAC&lt;/name&gt;
         &lt;synopsis&gt;
           Metadata indicating destination MAC address.
         &lt;/synopsis&gt;
         &lt;metadataID&gt;3&lt;/metadataID&gt;
         &lt;typeRef&gt;IEEEMAC&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;LogicalPortID&lt;/name&gt;
         &lt;synopsis&gt;Metadata of logical port ID&lt;/synopsis&gt;
         &lt;metadataID&gt;4&lt;/metadataID&gt;
         &lt;typeRef&gt;uint32&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;EtherType&lt;/name&gt;
         &lt;synopsis&gt;Metadata indicating Ethernet type&lt;/synopsis&gt;
         &lt;metadataID&gt;5&lt;/metadataID&gt;
         &lt;typeRef&gt;uint16&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;VlanID&lt;/name&gt;
         &lt;synopsis&gt;Metadata of VLAN ID&lt;/synopsis&gt;
         &lt;metadataID&gt;6&lt;/metadataID&gt;
         &lt;typeRef&gt;VlanIDType&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;VlanPriority&lt;/name&gt;
         &lt;synopsis&gt;Metadata of VLAN priority&lt;/synopsis&gt;
         &lt;metadataID&gt;7&lt;/metadataID&gt;
         &lt;typeRef&gt;VlanPriorityType&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;



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         &lt;name&gt;NextHopIPv4Addr&lt;/name&gt;
         &lt;synopsis&gt;
           Metadata representing a next-hop IPv4 address
         &lt;/synopsis&gt;
         &lt;metadataID&gt;8&lt;/metadataID&gt;
         &lt;typeRef&gt;IPv4Addr&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;NextHopIPv6Addr&lt;/name&gt;
         &lt;synopsis&gt;
           Metadata representing a next-hop IPv6 address
         &lt;/synopsis&gt;
         &lt;metadataID&gt;9&lt;/metadataID&gt;
         &lt;typeRef&gt;IPv6Addr&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;HopSelector&lt;/name&gt;
         &lt;synopsis&gt;Metadata indicating a hop selector&lt;/synopsis&gt;
         &lt;metadataID&gt;10&lt;/metadataID&gt;
         &lt;typeRef&gt;uint32&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;ExceptionID&lt;/name&gt;
         &lt;synopsis&gt;
           Metadata indicating exception types for exceptional cases
           during packet processing.
         &lt;/synopsis&gt;
         &lt;metadataID&gt;11&lt;/metadataID&gt;
         &lt;atomic&gt;
            &lt;baseType&gt;uint32&lt;/baseType&gt;
            &lt;specialValues&gt;
                &lt;specialValue value="0"&gt;
                  &lt;name&gt;AnyUnrecognizedExceptionCase&lt;/name&gt;
                  &lt;synopsis&gt;Any unrecognized exception case&lt;/synopsis&gt;
                  &lt;/specialValue&gt;
                &lt;specialValue value="1"&gt;
                  &lt;name&gt;ClassifyNoMatching&lt;/name&gt;
                  &lt;synopsis&gt;
                   Exception case: no matching of tables in
                   EtherClassifier LFB.
                  &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="2"&gt;
                  &lt;name&gt;MediaEncapInfoIndexInvalid&lt;/name&gt;
                  &lt;synopsis&gt;
                   Exception case: the MediaEncapInfoIndex value of
                   the packet is invalid and cannot be allocated in
                   the EncapTable in EtherEncap LFB.



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                  &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="3"&gt;
                  &lt;name&gt;EncapTableLookupFailed&lt;/name&gt;
                  &lt;synopsis&gt;
                   Exception case: the packet fails lookup of the
                   EncapTable table in EtherEncap LFB even though the
                   MediaEncapInfoIndex is valid.
                  &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="4"&gt;
                  &lt;name&gt;BadTTL&lt;/name&gt;
                  &lt;synopsis&gt;
                   Exception case: packet with expired TTL
                  &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="5"&gt;
                  &lt;name&gt;IPv4HeaderLengthMismatch&lt;/name&gt;
                  &lt;synopsis&gt;
                   Exception case: packet with header length more
                   than 5 words.
                  &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="6"&gt;
                   &lt;name&gt;RouterAlertOptions&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: packet IP head includes router
                    alert options.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="7"&gt;
                   &lt;name&gt;IPv6HopLimitZero&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: packet with the hop limit to zero.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="8"&gt;
                   &lt;name&gt;IPv6NextHeaderHBH&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: packet with next header set to
                    Hop-by-Hop.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="9"&gt;
                   &lt;name&gt;SrcAddressException&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: packet with exceptional source
                    address.



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                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="10"&gt;
                   &lt;name&gt;DstAddressException&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: packet with exceptional destination
                    address.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="11"&gt;
                   &lt;name&gt;LPMLookupFailed&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: packet failed the LPM table lookup
                    in a prefix match LFB.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="12"&gt;
                   &lt;name&gt;HopSelectorInvalid&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: HopSelector for the packet is
                    invalid.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="13"&gt;
                   &lt;name&gt;NextHopLookupFailed&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: packet failed lookup of a next-hop
                    table even though HopSelector is valid.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="14"&gt;
                   &lt;name&gt;FragRequired&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: packet fragmentation is required
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="15"&gt;
                   &lt;name&gt;MetadataNoMatching&lt;/name&gt;
                   &lt;synopsis&gt;
                    Exception case: there is no matching when looking
                    up the metadata dispatch table in
                    BasicMetadataDispatch LFB.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
             &lt;/specialValues&gt;
          &lt;/atomic&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;



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          &lt;name&gt;ValidateErrorID&lt;/name&gt;
          &lt;synopsis&gt;
            Metadata indicating error types when a packet passes
            validation process.
          &lt;/synopsis&gt;
          &lt;metadataID&gt;12&lt;/metadataID&gt;
          &lt;atomic&gt;
             &lt;baseType&gt;uint32&lt;/baseType&gt;
             &lt;specialValues&gt;
                &lt;specialValue value="0"&gt;
                   &lt;name&gt;AnyUnrecognizedValidateErrorCase&lt;/name&gt;
                   &lt;synopsis&gt;
                     Any unrecognized validate error case.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="1"&gt;
                   &lt;name&gt;InvalidIPv4PacketSize&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet length reported by the link
                    layer is less than 20 bytes.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="2"&gt;
                   &lt;name&gt;NotIPv4Packet&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet is not IP version 4&lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="3"&gt;
                   &lt;name&gt;InvalidIPv4HeaderLengthSize&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet with header length field in
                    the header less than 5 words.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="4"&gt;
                   &lt;name&gt;InvalidIPv4LengthFieldSize&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet with total length field in the
                    header less than 20 bytes.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="5"&gt;
                   &lt;name&gt;InvalidIPv4Checksum&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet with invalid checksum.
                    &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="6"&gt;



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                   &lt;name&gt;InvalidIPv4SrcAddr&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet with invalid IPv4 source
                    address.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="7"&gt;
                   &lt;name&gt;InvalidIPv4DstAddr&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet with invalid IPv4 destination
                    address.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="8"&gt;
                   &lt;name&gt;InvalidIPv6PacketSize&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet size is less than 40 bytes.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="9"&gt;
                   &lt;name&gt;NotIPv6Packet&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet is not IP version 6
                    &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="10"&gt;
                   &lt;name&gt;InvalidIPv6SrcAddr&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet with invalid IPv6 source address.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
                &lt;specialValue value="11"&gt;
                   &lt;name&gt;InvalidIPv6DstAddr&lt;/name&gt;
                   &lt;synopsis&gt;
                    Error case: packet with invalid IPv6 destination
                    address.
                   &lt;/synopsis&gt;
                &lt;/specialValue&gt;
             &lt;/specialValues&gt;
          &lt;/atomic&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;L3PortID&lt;/name&gt;
         &lt;synopsis&gt;
           Metadata indicating ID of an L3 logical port
         &lt;/synopsis&gt;
         &lt;metadataID&gt;13&lt;/metadataID&gt;
         &lt;typeRef&gt;uint32&lt;/typeRef&gt;



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      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;RedirectIndex&lt;/name&gt;
         &lt;synopsis&gt;
           Metadata that CE sends to RedirectIn LFB, indicating
           the index of the LFB group output port.
         &lt;/synopsis&gt;
         &lt;metadataID&gt;14&lt;/metadataID&gt;
         &lt;typeRef&gt;uint32&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
      &lt;metadataDef&gt;
         &lt;name&gt;MediaEncapInfoIndex&lt;/name&gt;
         &lt;synopsis&gt;
           A search key a packet uses to look up a table to select
           an encapsulation media.
         &lt;/synopsis&gt;
         &lt;metadataID&gt;15&lt;/metadataID&gt;
         &lt;typeRef&gt;uint32&lt;/typeRef&gt;
      &lt;/metadataDef&gt;
   &lt;/metadataDefs&gt;
&lt;/LFBLibrary&gt;

<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>.  LFB Class Descriptions</span>

   According to ForCES specifications, an LFB (Logical Function Block)
   is a well-defined, logically separable functional block that resides
   in an FE and is a functionally accurate abstraction of the FE's
   processing capabilities.  An LFB class (or type) is a template that
   represents a fine-grained, logically separable aspect of FE
   processing.  Most LFBs are related to packet processing in the data
   path.  LFB classes are the basic building blocks of the FE model.
   Note that [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>] has already defined an 'FE Protocol LFB', which
   is a logical entity in each FE to control the ForCES protocol.
   [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>] has already defined an 'FE Object LFB'.  Information like
   the FE Name, FE ID, FE State, and LFB Topology in the FE are
   represented in this LFB.

   As specified in <a href="#section-3.1">Section 3.1</a>, this document focuses on the base LFB
   library for implementing typical router functions, especially for IP
   forwarding functions.  As a result, LFB classes in the library are
   all base LFBs to implement router forwarding.

   In this section, the terms "upstream LFB" and "downstream LFB" are
   used.  These are used relative to the LFB that is being described.
   An "upstream LFB" is one whose output ports are connected to input
   ports of the LFB under consideration such that output (typically
   packets with metadata) can be sent from the "upstream LFB" to the LFB
   under consideration.  Similarly, a "downstream LFB" whose input ports



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   are connected to output ports of the LFB under consideration such
   that the LFB under consideration can send information to the
   "downstream LFB".  Note that in some rare topologies, an LFB may be
   both upstream and downstream relative to another LFB.

   Also note that, as a default provision of [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>], in the FE model,
   all metadata produced by upstream LFBs will pass through all
   downstream LFBs by default without being specified by input port or
   output port.  Only those metadata that will be used (consumed) by an
   LFB will be explicitly marked in the input of the LFB as expected
   metadata.  For instance, in downstream LFBs of a physical-layer LFB,
   even if there is no specific metadata expected, metadata like
   PHYPortID produced by the physical-layer LFB will always pass through
   all downstream LFBs regardless of whether or not the metadata has
   been expected by the LFBs.

<span class="h3"><a class="selflink" id="section-5.1" href="#section-5.1">5.1</a>.  Ethernet-Processing LFBs</span>

   As the most popular physical- and data-link-layer protocol, Ethernet
   is widely deployed.  It becomes a basic requirement for a router to
   be able to process various Ethernet data packets.

   Note that different versions of Ethernet formats exist, like Ethernet
   V2, 802.3 RAW, IEEE 802.3/802.2, and IEEE 802.3/802.2 SNAP.
   Varieties of LAN techniques based on Ethernet also exist, like
   various VLANs, MACinMAC, etc.  Ethernet-processing LFBs defined here
   are intended to be able to cope with all these variations of Ethernet
   technology.

   There are also various types of Ethernet physical interface media.
   Among them, copper and fiber media may be the most popular ones.  As
   a base LFB definition and a starting point, this document only
   defines an Ethernet physical LFB with copper media.  For other media
   interfaces, specific LFBs may be defined in future versions of the
   library.

<span class="h4"><a class="selflink" id="section-5.1.1" href="#section-5.1.1">5.1.1</a>.  EtherPHYCop</span>

   EtherPHYCop LFB abstracts an Ethernet interface physical layer with
   media limited to copper.

<span class="h5"><a class="selflink" id="section-5.1.1.1" href="#section-5.1.1.1">5.1.1.1</a>.  Data Handling</span>

   This LFB is the interface to the Ethernet physical media.  The LFB
   handles Ethernet frames coming in from or going out of the FE.
   Ethernet frames sent and received cover all packets encapsulated with
   different versions of Ethernet protocols, like Ethernet V2, 802.3
   RAW, IEEE 802.3/802.2, and IEEE 802.3/802.2 SNAP, including packets



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   encapsulated with varieties of LAN techniques based on Ethernet, like
   various VLANs, MACinMAC, etc.  Therefore, in the XML, an EthernetAll
   frame type has been introduced.

   Ethernet frames are received from the physical media port and passed
   downstream to LFBs, such as EtherMACIn LFBs, via a singleton output
   known as "EtherPHYOut".  A PHYPortID metadata, which indicates the
   physical port from which the frame came in from the external world,
   is passed along with the frame.

   Ethernet packets are received by this LFB from upstream LFBs, such as
   EtherMacOut LFBs, via the singleton input known as "EtherPHYIn"
   before being sent out to the external world.

<span class="h5"><a class="selflink" id="section-5.1.1.2" href="#section-5.1.1.2">5.1.1.2</a>.  Components</span>

   The AdminStatus component is defined for the CE to administratively
   manage the status of the LFB.  The CE may administratively start up
   or shut down the LFB by changing the value of AdminStatus.  The
   default value is set to 'Down'.

   An OperStatus component captures the physical port operational
   status.  A PHYPortStatusChanged event is defined so the LFB can
   report to the CE whenever there is an operational status change of
   the physical port.

   The PHYPortID component is a unique identification for a physical
   port.  It is defined as 'read-only' by the CE.  Its value is
   enumerated by FE.  The component will be used to produce a PHYPortID
   metadata at the LFB output and to associate it to every Ethernet
   packet this LFB receives.  The metadata will be handed to downstream
   LFBs for them to use the PHYPortID.

   A group of components are defined for link speed management.  The
   AdminLinkSpeed is for the CE to configure link speed for the port,
   and the OperLinkSpeed is for the CE to query the actual link speed in
   operation.  The default value for the AdminLinkSpeed is set to auto-
   negotiation mode.

   A group of components are defined for duplex mode management.  The
   AdminDuplexMode is for the CE to configure proper duplex mode for the
   port, and the OperDuplexMode is for CE to query the actual duplex
   mode in operation.  The default value for the AdminDuplexMode is set
   to auto-negotiation mode.

   A CarrierStatus component captures the status of the carrier and
   specifies whether the port link is operationally up.  The default
   value for the CarrierStatus is 'false'.



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<span class="h5"><a class="selflink" id="section-5.1.1.3" href="#section-5.1.1.3">5.1.1.3</a>.  Capabilities</span>

   The capability information for this LFB includes the link speeds that
   are supported by the FE (SupportedLinkSpeed) as well as the supported
   duplex modes (SupportedDuplexMode).

<span class="h5"><a class="selflink" id="section-5.1.1.4" href="#section-5.1.1.4">5.1.1.4</a>.  Events</span>

   Several events are generated.  There is an event for changes in the
   status of the physical port (PhyPortStatusChanged).  Such an event
   will notify that the physical port status has been changed, and the
   report will include the new status of the physical port.

   Another event captures changes in the operational link speed
   (LinkSpeedChanged).  Such an event will notify the CE that the
   operational speed has been changed, and the report will include the
   new negotiated operational speed.

   A final event captures changes in the duplex mode
   (DuplexModeChanged).  Such an event will notify the CE that the
   duplex mode has been changed and the report will include the new
   negotiated duplex mode.

<span class="h4"><a class="selflink" id="section-5.1.2" href="#section-5.1.2">5.1.2</a>.  EtherMACIn</span>

   EtherMACIn LFB abstracts an Ethernet port at the MAC data link layer.
   This LFB describes Ethernet processing functions like checking MAC
   address locality, deciding if the Ethernet packets should be bridged,
   providing Ethernet-layer flow control, etc.

<span class="h5"><a class="selflink" id="section-5.1.2.1" href="#section-5.1.2.1">5.1.2.1</a>.  Data Handling</span>

   The LFB is expected to receive all types of Ethernet packets (via a
   singleton input known as "EtherPktsIn"), which are usually output
   from some Ethernet physical-layer LFB, like an EtherPHYCop LFB, along
   with a metadata indicating the physical port ID of the port on which
   the packet arrived.

   The LFB is defined with two separate singleton outputs.  All output
   packets are emitted in the original Ethernet format received at the
   physical port, unchanged, and cover all Ethernet types.

   The first singleton output is known as "NormalPathOut".  It usually
   outputs Ethernet packets to some LFB, like an EtherClassifier LFB,
   for further L3 forwarding process along with a PHYPortID metadata
   indicating the physical port from which the packet came.





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   The second singleton output is known as "L2BridgingPathOut".
   Although the LFB library this document defines is basically to meet
   typical router functions, it will attempt to be forward compatible
   with future router functions.  The L2BridgingPathOut is defined to
   meet the requirement that L2 bridging functions may be optionally
   supported simultaneously with L3 processing and some L2 bridging LFBs
   that may be defined in the future.  If the FE supports L2 bridging,
   the CE can enable or disable it by means of a "L2BridgingPathEnable"
   component in the FE.  If it is enabled, by also instantiating some L2
   bridging LFB instances following the L2BridgingPathOut, FEs are
   expected to fulfill L2 bridging functions.  L2BridgingPathOut will
   output packets exactly the same as in the NormalPathOut output.

   This LFB can be set to work in a promiscuous mode, allowing all
   packets to pass through the LFB without being dropped.  Otherwise, a
   locality check will be performed based on the local MAC addresses.
   All packets that do not pass through the locality check will be
   dropped.

   This LFB can optionally participate in Ethernet flow control in
   cooperation with EtherMACOut LFB.  This document does not go into the
   details of how this is implemented.  This document also does not
   describe how the buffers that induce the flow control messages behave
   -- it is assumed that such artifacts exist, and describing them is
   out of scope in this document.

<span class="h5"><a class="selflink" id="section-5.1.2.2" href="#section-5.1.2.2">5.1.2.2</a>.  Components</span>

   The AdminStatus component is defined for the CE to administratively
   manage the status of the LFB.  The CE may administratively start up
   or shut down the LFB by changing the value of AdminStatus.  The
   default value is set to 'Down'.

   The LocalMACAddresses component specifies the local MAC addresses
   based on which locality checks will be made.  This component is an
   array of MAC addresses and of 'read-write' access permission.

   An L2BridgingPathEnable component captures whether the LFB is set to
   work as an L2 bridge.  An FE that does not support bridging will
   internally set this flag to false and additionally set the flag
   property as read-only.  The default value for the component is
   'false'.

   The PromiscuousMode component specifies whether the LFB is set to
   work in a promiscuous mode.  The default value for the component is
   'false'.





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   The TxFlowControl component defines whether the LFB is performing
   flow control on sending packets.  The default value is 'false'.  Note
   that the component is defined as "optional".  If an FE does not
   implement the component while a CE tries to configure the component
   to that FE, an error from the FE may be responded to the CE with an
   error code like 0x09 (E_COMPONENT_DOES_NOT_EXIST) or 0x15
   (E_NOT_SUPPORTED), depending on the FE processing.  See [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>] for
   details.

   The RxFlowControl component defines whether the LFB is performing
   flow control on receiving packets.  The default value is 'false'.
   The component is defined as "optional".

   A struct component, MACInStats, defines a set of statistics for this
   LFB, including the number of received packets and the number of
   dropped packets.  Note that this statistics component is optional to
   implementers.  If a CE tries to query the component while it is not
   implemented in an FE, an error code will be responded to the CE
   indicating the error type like 0x09 (E_COMPONENT_DOES_NOT_EXIST) or
   0x15 (E_NOT_SUPPORTED), depending on the FE implementation.

<span class="h5"><a class="selflink" id="section-5.1.2.3" href="#section-5.1.2.3">5.1.2.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.1.2.4" href="#section-5.1.2.4">5.1.2.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h4"><a class="selflink" id="section-5.1.3" href="#section-5.1.3">5.1.3</a>.  EtherClassifier</span>

   The EtherClassifier LFB abstracts the process to decapsulate Ethernet
   packets and then classify them.

<span class="h5"><a class="selflink" id="section-5.1.3.1" href="#section-5.1.3.1">5.1.3.1</a>.  Data Handling</span>

   This LFB describes the process of decapsulating Ethernet packets and
   classifying them into various network-layer data packets according to
   information included in the Ethernet packets headers.

   The LFB is expected to receive all types of Ethernet packets (via a
   singleton input known as "EtherPktsIn"), which are usually output
   from an upstream LFB like EtherMACIn LFB.  This input is also capable
   of multiplexing to allow for multiple upstream LFBs to be connected.
   For instance, when an L2 bridging function is enabled in the
   EtherMACIn LFB, some L2 bridging LFBs may be applied.  In this case,
   after L2 processing, some Ethernet packets may have to be input to
   the EtherClassifier LFB for classification, while simultaneously,



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   packets directly output from EtherMACIn may also need to input to
   this LFB.  This input is capable of handling such a case.  Usually,
   all expected Ethernet packets will be associated with a PHYPortID
   metadata, indicating the physical port from which the packet comes.
   In some cases, for instance, in a MACinMAC case, a LogicalPortID
   metadata may be expected to associate with the Ethernet packet to
   further indicate the logical port to which the Ethernet packet
   belongs.  Note that PHYPortID metadata is always expected while
   LogicalPortID metadata is optionally expected.

   Two output LFB ports are defined.

   The first output is a group output port known as "ClassifyOut".
   Types of network-layer protocol packets are output to instances of
   the port group.  Because there may be various types of protocol
   packets at the output ports, the produced output frame is defined as
   arbitrary for the purpose of wide extensibility in the future.
   Metadata to be carried along with the packet data is produced at this
   LFB for consumption by downstream LFBs.  The metadata passed
   downstream includes PHYPortID, as well as information on Ethernet
   type, source MAC address, destination MAC address, and the logical
   port ID.  If the original packet is a VLAN packet and contains a VLAN
   ID and a VLAN priority value, then the VLAN ID and the VLAN priority
   value are also carried downstream as metadata.  As a result, the VLAN
   ID and priority metadata are defined with the availability of
   "conditional".

   The second output is a singleton output port known as "ExceptionOut",
   which will output packets for which the data processing failed, along
   with an additional ExceptionID metadata to indicate what caused the
   exception.  Currently defined exception types include:

   o  There is no matching when classifying the packet.

   Usually, the ExceptionOut port may point to nowhere, indicating
   packets with exceptions are dropped, while in some cases, the output
   may be pointed to the path to the CE for further processing,
   depending on individual implementations.

<span class="h5"><a class="selflink" id="section-5.1.3.2" href="#section-5.1.3.2">5.1.3.2</a>.  Components</span>

   An EtherDispatchTable array component is defined in the LFB to
   dispatch every Ethernet packet to the output group according to the
   logical port ID assigned by the VlanInputTable to the packet and the
   Ethernet type in the Ethernet packet header.  Each row of the array
   is a struct containing a logical port ID, an EtherType and an output
   index.  With the CE configuring the dispatch table, the LFB can be
   expected to classify various network-layer protocol type packets and



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   output them at different output ports.  It is expected that the LFB
   classify packets according to protocols like IPv4, IPv6, MPLS,
   Address Resolution Protocol (ARP), Neighbor Discovery (ND), etc.

   A VlanInputTable array component is defined in the LFB to classify
   VLAN Ethernet packets.  Each row of the array is a struct containing
   an incoming port ID, a VLAN ID, and a logical port ID.  According to
   IEEE VLAN specifications, all Ethernet packets can be recognized as
   VLAN types by defining that if there is no VLAN encapsulation in a
   packet, a case with VLAN tag 0 is considered.  Every input packet is
   assigned with a new LogicalPortID according to the packet's incoming
   port ID and the VLAN ID.  A packet's incoming port ID is defined as a
   logical port ID if a logical port ID is associated with the packet or
   a physical port ID if no logical port ID is associated.  The VLAN ID
   is exactly the VLAN ID in the packet if it is a VLAN packet, or 0 if
   it is not.  Note that a logical port ID of a packet may be rewritten
   with a new one by the VlanInputTable processing.

   Note that the logical port ID and physical port ID mentioned above
   are all originally configured by the CE, and are globally effective
   within a ForCES NE (Network Element).  To distinguish a physical port
   ID from a logical port ID in the incoming port ID field of the
   VlanInputTable, physical port ID and logical port ID must be assigned
   with separate number spaces.

   An array component, EtherClassifyStats, defines a set of statistics
   for this LFB, measuring the number of packets per EtherType.  Each
   row of the array is a struct containing an EtherType and a packet
   number.  Note that this statistics component is optional to
   implementers.

<span class="h5"><a class="selflink" id="section-5.1.3.3" href="#section-5.1.3.3">5.1.3.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.1.3.4" href="#section-5.1.3.4">5.1.3.4</a>.  Events</span>

   This LFB has no events specified.

<span class="h4"><a class="selflink" id="section-5.1.4" href="#section-5.1.4">5.1.4</a>.  EtherEncap</span>

   The EtherEncap LFB abstracts the process to replace or attach
   appropriate Ethernet headers to the packet.

<span class="h5"><a class="selflink" id="section-5.1.4.1" href="#section-5.1.4.1">5.1.4.1</a>.  Data Handling</span>

   This LFB abstracts the process of encapsulating Ethernet headers onto
   received packets.  The encapsulation is based on passed metadata.



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   The LFB is expected to receive IPv4 and IPv6 packets (via a singleton
   input port known as "EncapIn"), which may be connected to an upstream
   LFB like IPv4NextHop, IPv6NextHop, BasicMetadataDispatch, or any LFB
   that requires output packets for Ethernet encapsulation.  The LFB
   always expects from upstream LFBs the MediaEncapInfoIndex metadata,
   which is used as a search key to look up the encapsulation table
   EncapTable by the search key matching the table index.  An input
   packet may also optionally receive a VLAN priority metadata,
   indicating that the packet originally had a priority value.  The
   priority value will be loaded back to the packet when encapsulating.
   The optional VLAN priority metadata is defined with a default value
   of 0.

   Two singleton output LFB ports are defined.

   The first singleton output is known as "SuccessOut".  Upon a
   successful table lookup, the destination and source MAC addresses and
   the logical media port (L2PortID) are found in the matching table
   entry.  The CE may set the VlanID in case VLANs are used.  By
   default, the table entry for VlanID of 0 is used as per IEEE rules
   [<a href="#ref-IEEE.802-1Q" title="&quot;IEEE Standard for Local and metropolitan area networks -- Media Access Control (MAC) Bridges and Virtual Bridged Local Area Networks&quot;">IEEE.802-1Q</a>].  Whatever the value of VlanID, if the input metadata
   VlanPriority is non-zero, the packet will have a VLAN tag.  If the
   VlanPriority and the VlanID are all zero, there is no VLAN tag for
   this packet.  After replacing or attaching the appropriate Ethernet
   headers to the packet is complete, the packet is passed out on the
   "SuccessOut" LFB port to a downstream LFB instance along with the
   L2PortID.

   The second singleton output is known as "ExceptionOut" and will
   output packets for which the table lookup fails, along with an
   additional ExceptionID metadata.  Currently defined exception types
   only include the following cases:

   o  The MediaEncapInfoIndex value of the packet is invalid and can not
      be allocated in the EncapTable.

   o  The packet failed lookup of the EncapTable table even though the
      MediaEncapInfoIndex is valid.

   The upstream LFB may be programmed by the CE to pass along a
   MediaEncapInfoIndex that does not exist in the EncapTable.  This
   allows for resolution of the L2 headers, if needed, to be made at the
   L2 encapsulation level, in this case, Ethernet via ARP or ND (or
   other methods depending on the link-layer technology), when a table
   miss occurs.

   For neighbor L2 header resolution (table miss exception), the
   processing LFB may pass this packet to the CE via the redirect LFB or



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   FE software or another LFB instance for further resolution.  In such
   a case, the metadata NextHopIPv4Addr or NextHopIPv6Addr generated by
   the next-hop LFB is also passed to the exception handling.  Such an
   IP address could be used to do activities such as ARP or ND by the
   handler to which it is passed.

   The result of the L2 resolution is to update the EncapTable as well
   as the next-hop LFB so subsequent packets do not fail EncapTable
   lookup.  The EtherEncap LFB does not make any assumptions of how the
   EncapTable is updated by the CE (or whether ARP/ND is used
   dynamically or static maps exist).

   Downstream LFB instances could be either an EtherMACOut type or a
   BasicMetadataDispatch type.  If the final packet L2 processing is on
   a per-media-port basis, resides on a different FE, or needs L2 header
   resolution, then it makes sense for the model to use a
   BasicMetadataDispatch LFB to fan out to different LFB instances.  If
   there is a direct egress port point, then it makes sense for the
   model to have a downstream LFB instance be an EtherMACOut.

<span class="h5"><a class="selflink" id="section-5.1.4.2" href="#section-5.1.4.2">5.1.4.2</a>.  Components</span>

   This LFB has only one component named EncapTable, which is defined as
   an array.  Each row of the array is a struct containing the
   destination MAC address, the source MAC address, the VLAN ID with a
   default value of zero, and the output logical L2 port ID.

<span class="h5"><a class="selflink" id="section-5.1.4.3" href="#section-5.1.4.3">5.1.4.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.1.4.4" href="#section-5.1.4.4">5.1.4.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h4"><a class="selflink" id="section-5.1.5" href="#section-5.1.5">5.1.5</a>.  EtherMACOut</span>

   The EtherMACOut LFB abstracts an Ethernet port at the MAC data link
   layer.  This LFB describes Ethernet packet output process.  Ethernet
   output functions are closely related to Ethernet input functions;
   therefore, many components defined in this LFB are aliases of
   EtherMACIn LFB components.









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<span class="h5"><a class="selflink" id="section-5.1.5.1" href="#section-5.1.5.1">5.1.5.1</a>.  Data Handling</span>

   The LFB is expected to receive all types of Ethernet packets (via a
   singleton input known as "EtherPktsIn"), which are usually output
   from an Ethernet encapsulation LFB along with a metadata indicating
   the ID of the physical port that the packet will go through.

   The LFB is defined with a singleton output port known as
   "EtherPktsOut".  All output packets are in Ethernet format, possibly
   with various Ethernet types, along with a metadata indicating the ID
   of the physical port that the packet is to go through.  This output
   links to a downstream LFB that is usually an Ethernet physical LFB
   like the EtherPHYCop LFB.

   This LFB can optionally participate in Ethernet flow control in
   cooperation with the EtherMACIn LFB.  This document does not go into
   the details of how this is implemented.  This document also does not
   describe how the buffers that induce the flow control messages behave
   -- it is assumed that such artifacts exist, but describing them is
   out of the scope of this document.

   Note that as a base definition, functions like multiple virtual MAC
   layers are not supported in this LFB version.  It may be supported in
   the future by defining a subclass or a new version of this LFB.

<span class="h5"><a class="selflink" id="section-5.1.5.2" href="#section-5.1.5.2">5.1.5.2</a>.  Components</span>

   The AdminStatus component is defined for the CE to administratively
   manage the status of the LFB.  The CE may administratively start up
   or shut down the LFB by changing the value of AdminStatus.  The
   default value is set to 'Down'.  Note that this component is defined
   as an alias of the AdminStatus component in the EtherMACIn LFB.  This
   infers that an EtherMACOut LFB usually coexists with an EtherMACIn
   LFB, both of which share the same administrative status management by
   the CE.  Alias properties, as defined in the ForCES FE model
   [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>], will be used by the CE to declare the target component to
   which the alias refers, which includes the target LFB class and
   instance IDs as well as the path to the target component.

   The MTU component defines the maximum transmission unit.

   The optional TxFlowControl component defines whether or not the LFB
   is performing flow control on sending packets.  The default value is
   'false'.  Note that this component is defined as an alias of the
   TxFlowControl component in the EtherMACIn LFB.

   The optional RxFlowControl component defines whether or not the LFB
   is performing flow control on receiving packets.  The default value



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   is 'false'.  Note that this component is defined as an alias of the
   RxFlowControl component in the EtherMACIn LFB.

   A struct component, MACOutStats, defines a set of statistics for this
   LFB, including the number of transmitted packets and the number of
   dropped packets.  This statistics component is optional to
   implementers.

<span class="h5"><a class="selflink" id="section-5.1.5.3" href="#section-5.1.5.3">5.1.5.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.1.5.4" href="#section-5.1.5.4">5.1.5.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h3"><a class="selflink" id="section-5.2" href="#section-5.2">5.2</a>.  IP Packet Validation LFBs</span>

   The LFBs are defined to abstract the IP packet validation process.
   An IPv4Validator LFB is specifically for IPv4 protocol validation,
   and an IPv6Validator LFB is specifically for IPv6.

<span class="h4"><a class="selflink" id="section-5.2.1" href="#section-5.2.1">5.2.1</a>.  IPv4Validator</span>

   The IPv4Validator LFB performs IPv4 packet validation.

<span class="h5"><a class="selflink" id="section-5.2.1.1" href="#section-5.2.1.1">5.2.1.1</a>.  Data Handling</span>

   This LFB performs IPv4 validation according to [<a href="./rfc1812" title="&quot;Requirements for IP Version 4 Routers&quot;">RFC1812</a>] and its
   updates.  The IPv4 packet will be output to the corresponding LFB
   port, indicating whether the packet is unicast or multicast or
   whether an exception has occurred or the validation failed.

   This LFB always expects, as input, packets that have been indicated
   as IPv4 packets by an upstream LFB, like an EtherClassifier LFB.
   There is no specific metadata expected by the input of the LFB.

   Four output LFB ports are defined.

   All validated IPv4 unicast packets will be output at the singleton
   port known as "IPv4UnicastOut".  All validated IPv4 multicast packets
   will be output at the singleton port known as "IPv4MulticastOut"
   port.

   A singleton port known as "ExceptionOut" is defined to output packets
   that have been validated as exception packets.  An exception ID
   metadata is produced to indicate what has caused the exception.  An
   exception case is the case when a packet needs further processing



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   before being normally forwarded.  Currently defined exception types
   include:

   o  Packet with expired TTL

   o  Packet with header length more than 5 words

   o  Packet IP head including router alert options

   o  Packet with exceptional source address

   o  Packet with exceptional destination address

   Note that although Time to Live (TTL) is checked in this LFB for
   validity, operations like TTL decrement are made by the downstream
   forwarding LFB.

   The final singleton port known as "FailOut" is defined for all
   packets that have errors and failed the validation process.  An error
   case is when a packet is unable to be further processed or forwarded
   without being dropped.  An error ID is associated with a packet to
   indicate the failure reason.  Currently defined failure reasons
   include:

   o  Packet with size reported less than 20 bytes

   o  Packet with version not IPv4

   o  Packet with header length less than 5 words

   o  Packet with total length field less than 20 bytes

   o  Packet with invalid checksum

   o  Packet with invalid source address

   o  Packet with invalid destination address

<span class="h5"><a class="selflink" id="section-5.2.1.2" href="#section-5.2.1.2">5.2.1.2</a>.  Components</span>

   This LFB has only one struct component, the
   IPv4ValidatorStatisticsType, which defines a set of statistics for
   validation process, including the number of bad header packets, the
   number of bad total length packets, the number of bad TTL packets,
   and the number of bad checksum packets.  This statistics component is
   optional to implementers.





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<span class="h5"><a class="selflink" id="section-5.2.1.3" href="#section-5.2.1.3">5.2.1.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities

<span class="h5"><a class="selflink" id="section-5.2.1.4" href="#section-5.2.1.4">5.2.1.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h4"><a class="selflink" id="section-5.2.2" href="#section-5.2.2">5.2.2</a>.  IPv6Validator</span>

   The IPv6Validator LFB performs IPv6 packet validation.

<span class="h5"><a class="selflink" id="section-5.2.2.1" href="#section-5.2.2.1">5.2.2.1</a>.  Data Handling</span>

   This LFB performs IPv6 validation according to [<a href="./rfc2460" title="&quot;Internet Protocol, Version 6 (IPv6) Specification&quot;">RFC2460</a>] and its
   updates.  Then the IPv6 packet will be output to the corresponding
   port regarding of the validation result, indicating whether the
   packet is a unicast or a multicast one, an exception has occurred or
   the validation failed.

   This LFB always expects, as input, packets that have been indicated
   as IPv6 packets by an upstream LFB, like an EtherClassifier LFB.
   There is no specific metadata expected by the input of the LFB.

   Similar to the IPv4validator LFB, the IPv6Validator LFB has also
   defined four output ports to emit packets with various validation
   results.

   All validated IPv6 unicast packets will be output at the singleton
   port known as "IPv6UnicastOut".  All validated IPv6 multicast packets
   will be output at the singleton port known as "IPv6MulticastOut".
   There is no metadata produced at this LFB.

   A singleton port known as "ExceptionOut" is defined to output packets
   that have been validated as exception packets.  An exception case is
   when a packet needs further processing before being normally
   forwarded.  An exception ID metadata is produced to indicate what
   caused the exception.  Currently defined exception types include:

   o  Packet with hop limit to zero

   o  Packet with next header set to hop-by-hop

   o  Packet with exceptional source address

   o  Packet with exceptional destination address





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   The final singleton port known as "FailOut" is defined for all
   packets that have errors and failed the validation process.  An error
   case when a packet is unable to be further processed or forwarded
   without being dropped.  A validate error ID is associated to every
   failed packet to indicate the reason.  Currently defined reasons
   include:

   o  Packet with size reported less than 40 bytes

   o  Packet with version not IPv6

   o  Packet with invalid source address

   o  Packet with invalid destination address

   Note that in the base type library, definitions for exception ID and
   validate error ID metadata are applied to both IPv4Validator and
   IPv6Validator LFBs, i.e., the two LFBs share the same metadata
   definition, with different ID assignment inside.

<span class="h5"><a class="selflink" id="section-5.2.2.2" href="#section-5.2.2.2">5.2.2.2</a>.  Components</span>

   This LFB has only one struct component, the
   IPv6ValidatorStatisticsType, which defines a set of statistics for
   the validation process, including the number of bad header packets,
   the number of bad total length packets, and the number of bad hop
   limit packets.  Note that this component is optional to implementers.

<span class="h5"><a class="selflink" id="section-5.2.2.3" href="#section-5.2.2.3">5.2.2.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.2.2.4" href="#section-5.2.2.4">5.2.2.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h3"><a class="selflink" id="section-5.3" href="#section-5.3">5.3</a>.  IP Forwarding LFBs</span>

   IP Forwarding LFBs are specifically defined to abstract the IP
   forwarding processes.  As definitions for a base LFB library, this
   document restricts its LFB definition scope only to IP unicast
   forwarding.  IP multicast may be defined in future documents.

   The two fundamental tasks performed in IP unicast forwarding
   constitute looking up the forwarding information table to find next-
   hop information and then using the resulting next-hop details to
   forward packets out on specific physical output ports.  This document
   models the forwarding processes by abstracting out the described two



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   steps.  Whereas this document describes functional LFB models that
   are modular, there may be multiple ways to implement the abstracted
   models.  It is not intended or expected that the provided LFB models
   constrain implementations.

   Based on the IP forwarding abstraction, two kinds of typical IP
   unicast forwarding LFBs are defined: unicast LPM lookup LFB and next-
   hop application LFB.  They are further distinguished by IPv4 and IPv6
   protocols.

<span class="h4"><a class="selflink" id="section-5.3.1" href="#section-5.3.1">5.3.1</a>.  IPv4UcastLPM</span>

   The IPv4UcastLPM LFB abstracts the IPv4 unicast Longest Prefix Match
   (LPM) process.

   This LFB also provides facilities to support users to implement
   equal-cost multipath (ECMP) routing or reverse path forwarding (RPF).
   However, this LFB itself does not provide ECMP or RPF.  To fully
   implement ECMP or RPF, additional specific LFBs, like a specific ECMP
   LFB or an RPF LFB, will have to be defined.

<span class="h5"><a class="selflink" id="section-5.3.1.1" href="#section-5.3.1.1">5.3.1.1</a>.  Data Handling</span>

   This LFB performs the IPv4 unicast LPM table lookup.  It always
   expects as input IPv4 unicast packets from one singleton input known
   as "PktsIn".  Then, the LFB uses the destination IPv4 address of
   every packet as a search key to look up the IPv4 prefix table and
   generate a hop selector as the matching result.  The hop selector is
   passed as packet metadata to downstream LFBs and will usually be used
   there as a search index to find more next-hop information.

   Three singleton output LFB ports are defined.

   The first singleton output is known as "NormalOut" and outputs IPv4
   unicast packets that succeed the LPM lookup (and got a hop selector).
   The hop selector is associated with the packet as a metadata.
   Downstream from the LPM LFB is usually a next-hop application LFB,
   like an IPv4NextHop LFB.

   The second singleton output is known as "ECMPOut" and is defined to
   provide support for users wishing to implement ECMP.

   An ECMP flag is defined in the LPM table to enable the LFB to support
   ECMP.  When a table entry is created with the flag set to true, it
   indicates this table entry is for ECMP only.  A packet that has
   passed through this prefix lookup will always output from the
   "ECMPOut" output port, with the hop selector being its lookup result.
   The output will usually go directly to a downstream ECMP processing



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   LFB, where the hop selector can usually further generate optimized
   one or multiple next-hop routes by use of ECMP algorithms.

   A default route flag is defined in the LPM table to enable the LFB to
   support a default route as well as loose RPF.  When this flag is set
   to true, the table entry is identified as a default route, which also
   implies that the route is forbidden for RPF.  If a user wants to
   implement RPF on FE, a specific RPF LFB will have to be defined.  In
   such an RPF LFB, a component can be defined as an alias of the prefix
   table component of this LFB, as described below.

   The final singleton output is known as "ExceptionOut" of the
   IPv4UcastLPM LFB and is defined to output exception packets after the
   LFB processing, along with an ExceptionID metadata to indicate what
   caused the exception.  Currently defined exception types include:

   o  The packet failed the LPM lookup of the prefix table.

   The upstream LFB of this LFB is usually an IPv4Validator LFB.  If RPF
   is to be adopted, the upstream can be an RPF LFB, when defined.

   The downstream LFB is usually an IPv4NextHop LFB.  If ECMP is
   adopted, the downstream can be an ECMP LFB, when defined.

<span class="h5"><a class="selflink" id="section-5.3.1.2" href="#section-5.3.1.2">5.3.1.2</a>.  Components</span>

   This LFB has two components.

   The IPv4PrefixTable component is defined as an array component of the
   LFB.  Each row of the array contains an IPv4 address, a prefix
   length, a hop selector, an ECMP flag and a default route flag.  The
   LFB uses the destination IPv4 address of every input packet as a
   search key to look up this table in order extract a next-hop
   selector.  The ECMP flag is for the LFB to support ECMP.  The default
   route flag is for the LFB to support a default route and for loose
   RPF.

   The IPv4UcastLPMStats component is a struct component that collects
   statistics information, including the total number of input packets
   received, the IPv4 packets forwarded by this LFB, and the number of
   IP datagrams discarded due to no route found.  Note that this
   component is defined as optional to implementers.

<span class="h5"><a class="selflink" id="section-5.3.1.3" href="#section-5.3.1.3">5.3.1.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.





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<span class="h5"><a class="selflink" id="section-5.3.1.4" href="#section-5.3.1.4">5.3.1.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h4"><a class="selflink" id="section-5.3.2" href="#section-5.3.2">5.3.2</a>.  IPv4NextHop</span>

   This LFB abstracts the process of selecting IPv4 next-hop action.

<span class="h5"><a class="selflink" id="section-5.3.2.1" href="#section-5.3.2.1">5.3.2.1</a>.  Data Handling</span>

   The LFB abstracts the process of next-hop information application to
   IPv4 packets.  It receives an IPv4 packet with an associated next-hop
   identifier (HopSelector) and uses the identifier as a table index to
   look up a next-hop table to find an appropriate LFB output port.

   The LFB is expected to receive unicast IPv4 packets, via a singleton
   input known as "PktsIn", along with a HopSelector metadata, which is
   used as a table index to look up the NextHop table.  The data
   processing involves the forwarding TTL decrement and IP checksum
   recalculation.

   Two output LFB ports are defined.

   The first output is a group output port known as "SuccessOut".  On
   successful data processing, the packet is sent out from an LFB port
   from within the LFB port group as selected by the
   LFBOutputSelectIndex value of the matched table entry.  The packet is
   sent to a downstream LFB along with the L3PortID and
   MediaEncapInfoIndex metadata.

   The second output is a singleton output port known as "ExceptionOut",
   which will output packets for which the data processing failed, along
   with an additional ExceptionID metadata to indicate what caused the
   exception.  Currently defined exception types include:

   o  The HopSelector for the packet is invalid.

   o  The packet failed lookup of the next-hop table even though the
      HopSelector is valid.

   o  The MTU for outgoing interface is less than the packet size.

   Downstream LFB instances could be either a BasicMetadataDispatch type
   (<a href="#section-5.5.1">Section 5.5.1</a>), used to fan out to different LFB instances or a
   media-encapsulation-related type, such as an EtherEncap type or a
   RedirectOut type (<a href="#section-5.4.2">Section 5.4.2</a>).  For example, if there are Ethernet
   and other tunnel encapsulation, then a BasicMetadataDispatch LFB can




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   use the L3PortID metadata (<a href="#section-5.3.2.2">Section 5.3.2.2</a>) to dispatch packets to a
   different encapsulator.

<span class="h5"><a class="selflink" id="section-5.3.2.2" href="#section-5.3.2.2">5.3.2.2</a>.  Components</span>

   This LFB has only one component, IPv4NextHopTable, which is defined
   as an array.  The HopSelector received is used to match the array
   index of IPv4NextHopTable to find out a row of the table as the next-
   hop information result.  Each row of the array is a struct
   containing:

   o  The L3PortID, which is the ID of the logical output port that is
      passed on to the downstream LFB instance.  This ID indicates what
      kind of encapsulating port the neighbor is to use.  This is L3-
      derived information that affects L2 processing and so needs to be
      based from one LFB to another as metadata.  Usually, this ID is
      used for the next-hop LFB to distinguish packets that need
      different L2 encapsulating.  For instance, some packets may
      require general Ethernet encapsulation while others may require
      various types of tunnel encapsulations.  In such a case, different
      L3PortIDs are assigned to the packets and are passed as metadata
      to a downstream LFB.  A BasicMetadataDispatch LFB (<a href="#section-5.5.1">Section 5.5.1</a>)
      may have to be applied as the downstream LFB so as to dispatch
      packets to different encapsulation LFB instances according to the
      L3PortIDs.

   o  MTU, the Maximum Transmission Unit for the outgoing port.

   o  NextHopIPAddr, the IPv4 next-hop address.

   o  MediaEncapInfoIndex, the index that passes on to the downstream
      encapsulation LFB instance and that is used there as a search key
      to look up a table (typically media-encapsulation-related) for
      further encapsulation information.  The search key looks up the
      table by matching the table index.  Note that the encapsulation
      LFB instance that uses this metadata may not be the LFB instance
      that immediately follows this LFB instance in the processing.  The
      MediaEncapInfoIndex metadata is attached here and is passed
      through intermediate LFBs until it is used by the encapsulation
      LFB instance.  In some cases, depending on implementation, the CE
      may set the MediaEncapInfoIndex passed downstream to a value that
      will fail lookup when it gets to a target encapsulation LFB; such
      a lookup failure at that point is an indication that further
      resolution is needed.  For an example of this approach, refer to
      <a href="#section-7.2">Section 7.2</a>, which discusses ARP and mentions this approach.






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   o  LFBOutputSelectIndex, the LFB group output port index to select
      the downstream LFB port.  This value identifies the specific port
      within the SuccessOut port group out of which packets that
      successfully use this next-hop entry are to be sent.

<span class="h5"><a class="selflink" id="section-5.3.2.3" href="#section-5.3.2.3">5.3.2.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.3.2.4" href="#section-5.3.2.4">5.3.2.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h4"><a class="selflink" id="section-5.3.3" href="#section-5.3.3">5.3.3</a>.  IPv6UcastLPM</span>

   The IPv6UcastLPM LFB abstracts the IPv6 unicast Longest Prefix Match
   (LPM) process.  The definition of this LFB is similar to the
   IPv4UcastLPM LFB except that all IP addresses refer to IPv6
   addresses.

   This LFB also provides facilities to support users to implement
   equal-cost multipath (ECMP) routing or reverse path forwarding (RPF).
   However, this LFB itself does not provide ECMP or RPF.  To fully
   implement ECMP or RPF, additional specific LFBs, like a specific ECMP
   LFB or an RPF LFB, will have to be defined.  This work may be done in
   future versions of this document.

<span class="h5"><a class="selflink" id="section-5.3.3.1" href="#section-5.3.3.1">5.3.3.1</a>.  Data Handling</span>

   This LFB performs the IPv6 unicast LPM table lookup.  It always
   expects as input IPv6 unicast packets from one singleton input known
   as "PktsIn".  The destination IPv6 address of an incoming packet is
   used as a search key to look up the IPv6 prefix table and generate a
   hop selector.  This hop selector result is associated to the packet
   as a metadata and sent to downstream LFBs; it will usually be used in
   downstream LFBs as a search key to find more next-hop information.

   Three singleton output LFB ports are defined.

   The first singleton output is known as "NormalOut" and outputs IPv6
   unicast packets that succeed the LPM lookup (and got a hop selector).
   The hop selector is associated with the packet as a metadata.
   Downstream from the LPM LFB is usually a next-hop application LFB,
   like an IPv6NextHop LFB.

   The second singleton output is known as "ECMPOut" and is defined to
   provide support for users wishing to implement ECMP.




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   An ECMP flag is defined in the LPM table to enable the LFB to support
   ECMP.  When a table entry is created with the flag set to true, it
   indicates this table entry is for ECMP only.  A packet that has
   passed through this prefix lookup will always output from the
   "ECMPOut" output port, with the hop selector being its lookup result.
   The output will usually go directly to a downstream ECMP processing
   LFB, where the hop selector can usually further generate optimized
   one or multiple next-hop routes by use of ECMP algorithms.

   A default route flag is defined in the LPM table to enable the LFB to
   support a default route as well as loose RPF.  When this flag is set
   to true, the table entry is identified as a default route, which also
   implies that the route is forbidden for RPF.

   If a user wants to implement RPF on FE, a specific RPF LFB will have
   to be defined.  In such an RPF LFB, a component can be defined as an
   alias of the prefix table component of this LFB, as described below.

   The final singleton output is known as "ExceptionOut" of the
   IPv6UcastLPM LFB and is defined to output exception packets after the
   LFB processing, along with an ExceptionID metadata to indicate what
   caused the exception.  Currently defined exception types include:

   o  The packet failed the LPM lookup of the prefix table.

   The upstream LFB of this LFB is usually an IPv6Validator LFB.  If RPF
   is to be adopted, the upstream can be an RPF LFB, when defined.

   The downstream LFB is usually an IPv6NextHop LFB.  If ECMP is
   adopted, the downstream can be an ECMP LFB, when defined.

<span class="h5"><a class="selflink" id="section-5.3.3.2" href="#section-5.3.3.2">5.3.3.2</a>.  Components</span>

   This LFB has two components.

   The IPv6PrefixTable component is defined as an array component of the
   LFB.  Each row of the array contains an IPv6 address, a prefix
   length, a hop selector, an ECMP flag, and a default route flag.  The
   ECMP flag is so the LFB can support ECMP.  The default route flag is
   for the LFB to support a default route and for loose RPF, as
   described earlier.

   The IPv6UcastLPMStats component is a struct component that collects
   statistics information, including the total number of input packets
   received, the IPv6 packets forwarded by this LFB and the number of IP
   datagrams discarded due to no route found.  Note that the component
   is defined as optional to implementers.




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<span class="h5"><a class="selflink" id="section-5.3.3.3" href="#section-5.3.3.3">5.3.3.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.3.3.4" href="#section-5.3.3.4">5.3.3.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h4"><a class="selflink" id="section-5.3.4" href="#section-5.3.4">5.3.4</a>.  IPv6NextHop</span>

   This LFB abstracts the process of selecting IPv6 next-hop action.

<span class="h5"><a class="selflink" id="section-5.3.4.1" href="#section-5.3.4.1">5.3.4.1</a>.  Data Handling</span>

   The LFB abstracts the process of next-hop information application to
   IPv6 packets.  It receives an IPv6 packet with an associated next-hop
   identifier (HopSelector) and uses the identifier to look up a next-
   hop table to find an appropriate output port from the LFB.

   The LFB is expected to receive unicast IPv6 packets, via a singleton
   input known as "PktsIn", along with a HopSelector metadata, which is
   used as a table index to look up the next-hop table.

   Two output LFB ports are defined.

   The first output is a group output port known as "SuccessOut".  On
   successful data processing, the packet is sent out from an LFB port
   from within the LFB port group as selected by the
   LFBOutputSelectIndex value of the matched table entry.  The packet is
   sent to a downstream LFB along with the L3PortID and
   MediaEncapInfoIndex metadata.

   The second output is a singleton output port known as "ExceptionOut",
   which will output packets for which the data processing failed, along
   with an additional ExceptionID metadata to indicate what caused the
   exception.  Currently defined exception types include:

   o  The HopSelector for the packet is invalid.

   o  The packet failed lookup of the next-hop table even though the
      HopSelector is valid.

   o  The MTU for outgoing interface is less than the packet size.

   Downstream LFB instances could be either a BasicMetadataDispatch
   type, used to fan out to different LFB instances, or a media
   encapsulation related type, such as an EtherEncap type or a
   RedirectOut type.  For example, when the downstream LFB is



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   BasicMetadataDispatch and Ethernet and other tunnel encapsulation
   exist downstream from BasicMetadataDispatch, then the
   BasicMetadataDispatch LFB can use the L3PortID metadata (see section
   below) to dispatch packets to the different encapsulator LFBs.

<span class="h5"><a class="selflink" id="section-5.3.4.2" href="#section-5.3.4.2">5.3.4.2</a>.  Components</span>

   This LFB has only one component named IPv6NextHopTable, which is
   defined as an array.  The array index of IPv6NextHopTable is used for
   a HopSelector to find out a row of the table as the next-hop
   information.  Each row of the array is a struct containing:

   o  The L3PortID, which is the ID of the logical output port that is
      passed onto the downstream LFB instance.  This ID indicates what
      kind of encapsulating port the neighbor is to use.  This is L3-
      derived information that affects L2 processing and so needs to be
      based from one LFB to another as metadata.  Usually, this ID is
      used for the next-hop LFB to distinguish packets that need
      different L2 encapsulating.  For instance, some packets may
      require general Ethernet encapsulation while others may require
      various types of tunnel encapsulations.  In such a case, different
      L3PortIDs are assigned to the packets and are passed as metadata
      to a downstream LFB.  A BasicMetadataDispatch LFB (<a href="#section-5.5.1">Section 5.5.1</a>)
      may have to be applied as the downstream LFB so as to dispatch
      packets to different encapsulation LFB instances according to the
      L3PortIDs.

   o  MTU, the Maximum Transmission Unit for the outgoing port.

   o  NextHopIPAddr, the IPv6 next-hop address.

   o  MediaEncapInfoIndex, the index that is passed on to the downstream
      encapsulation LFB instance and that is used there as a search key
      to look up a table (typically media-encapsulation-related) for
      further encapsulation information.  The search key looks up the
      table by matching the table index.  Note that the encapsulation
      LFB instance that uses this metadata may not be the LFB instance
      that immediately follows this LFB instance in the processing.  The
      MediaEncapInfoIndex metadata is attached here and is passed
      through intermediate LFBs until it is used by the encapsulation
      LFB instance.  In some cases, depending on implementation, the CE
      may set the MediaEncapInfoIndex passed downstream to a value that
      will fail lookup when it gets to a target encapsulation LFB; such
      a lookup failure at that point is an indication that further
      resolution is needed.  For an example of this approach, refer to
      <a href="#section-7.2">Section 7.2</a>, which discusses ARP and mentions this approach.





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   o  LFBOutputSelectIndex, the LFB group output port index to select
      the downstream LFB port.  This value identifies the specific port
      within the SuccessOut port group out of which packets that
      successfully use this next-hop entry are to be sent.

<span class="h5"><a class="selflink" id="section-5.3.4.3" href="#section-5.3.4.3">5.3.4.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.3.4.4" href="#section-5.3.4.4">5.3.4.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h3"><a class="selflink" id="section-5.4" href="#section-5.4">5.4</a>.  Redirect LFBs</span>

   Redirect LFBs abstract the data packet transportation process between
   the CE and FE.  Some packets output from some LFBs may have to be
   delivered to the CE for further processing, and some packets
   generated by the CE may have to be delivered to the FE and further to
   some specific LFBs for data path processing.  According to [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>],
   data packets and their associated metadata are encapsulated in a
   ForCES redirect message for transportation between CE and FE.  We
   define two LFBs to abstract the process: a RedirectIn LFB and a
   RedirectOut LFB.  Usually, in an LFB topology of an FE, only one
   RedirectIn LFB instance and one RedirectOut LFB instance exist.

<span class="h4"><a class="selflink" id="section-5.4.1" href="#section-5.4.1">5.4.1</a>.  RedirectIn</span>

   The RedirectIn LFB abstracts the process for the CE to inject data
   packets into the FE data path.

<span class="h5"><a class="selflink" id="section-5.4.1.1" href="#section-5.4.1.1">5.4.1.1</a>.  Data Handling</span>

   A RedirectIn LFB abstracts the process for the CE to inject data
   packets into the FE LFB topology so as to input data packets into FE
   data paths.  From the LFB topology's point of view, the RedirectIn
   LFB acts as a source point for data packets coming from the CE;
   therefore, the RedirectIn LFB is defined with a single output LFB
   port (and no input LFB port).

   The single output port of RedirectIn LFB is defined as a group output
   type with the name of "PktsOut".  Packets produced by this output
   will have arbitrary frame types decided by the CE that generated the
   packets.  Possible frames may include IPv4, IPv6, or ARP protocol
   packets.  The CE may associate some metadata to indicate the frame
   types and may also associate other metadata to indicate various
   information on the packets.  Among them, there MUST exist a
   RedirectIndex metadata, which is an integer acting as an index.  When



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   the CE transmits the metadata along with the packet to a RedirectIn
   LFB, the LFB will read the RedirectIndex metadata and output the
   packet to one of its group output port instances, whose port index is
   indicated by this metadata.  Any other metadata, in addition to
   RedirectIndex, will be passed untouched along the packet delivered by
   the CE to the downstream LFB.  This means the RedirectIndex metadata
   from CE will be "consumed" by the RedirectIn LFB and will not be
   passed to downstream LFB.  Note that a packet from the CE without a
   RedirectIndex metadata associated will be dropped by the LFB.  Note
   that all metadata visible to the LFB need to be global and IANA
   controlled.  See <a href="#section-8">Section 8</a> ("IANA Considerations") of this document
   for more details about a metadata ID space that can be used by
   vendors and is "Reserved for Private Use".

<span class="h5"><a class="selflink" id="section-5.4.1.2" href="#section-5.4.1.2">5.4.1.2</a>.  Components</span>

   An optional statistics component is defined to collect the number of
   packets received by the LFB from the CE.  There are no other
   components defined for the current version of the LFB.

<span class="h5"><a class="selflink" id="section-5.4.1.3" href="#section-5.4.1.3">5.4.1.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.4.1.4" href="#section-5.4.1.4">5.4.1.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h4"><a class="selflink" id="section-5.4.2" href="#section-5.4.2">5.4.2</a>.  RedirectOut</span>

   RedirectOut LFB abstracts the process for LFBs in the FE to deliver
   data packets to the CE.

<span class="h5"><a class="selflink" id="section-5.4.2.1" href="#section-5.4.2.1">5.4.2.1</a>.  Data Handling</span>

   A RedirectOut LFB abstracts the process for LFBs in the FE to deliver
   data packets to the CE.  From the LFB topology's point of view, the
   RedirectOut LFB acts as a sink point for data packets going to the
   CE; therefore, the RedirectOut LFB is defined with a single input LFB
   port (and no output LFB port).

   The RedirectOut LFB has only one singleton input, known as "PktsIn",
   but is capable of receiving packets from multiple LFBs by
   multiplexing this input.  The input expects any kind of frame type;
   therefore, the frame type has been specified as arbitrary, and also
   all types of metadata are expected.  All associated metadata produced
   (but not consumed) by previous processed LFBs should be delivered to
   the CE via the ForCES protocol redirect message [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>].  The CE



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   can decide how to process the redirected packet by referencing the
   associated metadata.  As an example, a packet could be redirected by
   the FE to the CE because the EtherEncap LFB is not able to resolve L2
   information.  The metadata "ExceptionID" created by the EtherEncap
   LFB is passed along with the packet and should be sufficient for the
   CE to do the necessary processing and resolve the L2 entry required.
   Note that all metadata visible to the LFB need to be global and IANA
   controlled.  See <a href="#section-8">Section 8</a> ("IANA Considerations") of this document
   for more details about a metadata ID space that can be used by
   vendors and is "Reserved for Private Use".

<span class="h5"><a class="selflink" id="section-5.4.2.2" href="#section-5.4.2.2">5.4.2.2</a>.  Components</span>

   An optional statistics component is defined to collect the number of
   packets sent by the LFB to the CE.  There are no other components
   defined for the current version of the LFB.

<span class="h5"><a class="selflink" id="section-5.4.2.3" href="#section-5.4.2.3">5.4.2.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.

<span class="h5"><a class="selflink" id="section-5.4.2.4" href="#section-5.4.2.4">5.4.2.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h3"><a class="selflink" id="section-5.5" href="#section-5.5">5.5</a>.  General Purpose LFBs</span>

<span class="h4"><a class="selflink" id="section-5.5.1" href="#section-5.5.1">5.5.1</a>.  BasicMetadataDispatch</span>

   The BasicMetadataDispatch LFB is defined to abstract the process in
   which a packet is dispatched to some output path based on its
   associated metadata value.

<span class="h5"><a class="selflink" id="section-5.5.1.1" href="#section-5.5.1.1">5.5.1.1</a>.  Data Handling</span>

   The BasicMetadataDispatch LFB has only one singleton input known as
   "PktsIn".  Every input packet should be associated with a metadata
   that will be used by the LFB to do the dispatch.  This LFB contains a
   metadata ID and a dispatch table named MetadataDispatchTable, all
   configured by the CE.  The metadata ID specifies which metadata is to
   be used for dispatching packets.  The MetadataDispatchTable contains
   entries of a metadata value and an OutputIndex, specifying that the
   packet with the metadata value must go out from the LFB group output
   port instance with the OutputIndex.

   Two output LFB ports are defined.





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   The first output is a group output port known as "PktsOut".  A packet
   with its associated metadata having found an OutputIndex by
   successfully looking up the dispatch table will be output to the
   group port instance with the corresponding index.

   The second output is a singleton output port known as "ExceptionOut",
   which will output packets for which the data processing failed, along
   with an additional ExceptionID metadata to indicate what caused the
   exception.  Currently defined exception types only include one case:

   o  There is no matching when looking up the metadata dispatch table.

   As an example, if the CE decides to dispatch packets according to a
   physical port ID (PHYPortID), the CE may set the ID of PHYPortID
   metadata to the LFB first.  Moreover, the CE also sets the PHYPortID
   actual values (the metadata values) and assigned OutputIndex for the
   values to the dispatch table in the LFB.  When a packet arrives, a
   PHYPortID metadata is found associated with the packet, and the
   metadata value is further used as a key to look up the dispatch table
   to find out an output port instance for the packet.

   Currently, the BasicMetadataDispatch LFB only allows the metadata
   value of the dispatch table entry to be a 32-bit integer.  A metadata
   with other value types is not supported in this version.  A more
   complex metadata dispatch LFB may be defined in future versions of
   the library.  In that LFB, multiple tuples of metadata with more
   value types supported may be used to dispatch packets.

<span class="h5"><a class="selflink" id="section-5.5.1.2" href="#section-5.5.1.2">5.5.1.2</a>.  Components</span>

   This LFB has two components.  One component is MetadataID and the
   other is MetadataDispatchTable.  Each row entry of the dispatch table
   is a struct containing the metadata value and the OutputIndex.  Note
   that currently, the metadata value is only allowed to be a 32-bit
   integer.  The metadata value is also defined as a content key for the
   table.  The concept of content key is a searching key for tables,
   which is defined in the ForCES FE model [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>].  With the content
   key, the CE can manipulate the table by means of a specific metadata
   value rather than by the table index only.  See the ForCES FE model
   [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>] and also the ForCES protocol [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>] for more details on
   the definition and use of a content key.

<span class="h5"><a class="selflink" id="section-5.5.1.3" href="#section-5.5.1.3">5.5.1.3</a>.  Capabilities</span>

   This LFB does not have a list of capabilities.






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<span class="h5"><a class="selflink" id="section-5.5.1.4" href="#section-5.5.1.4">5.5.1.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h4"><a class="selflink" id="section-5.5.2" href="#section-5.5.2">5.5.2</a>.  GenericScheduler</span>

   This is a preliminary generic scheduler LFB for abstracting a simple
   scheduling process.

<span class="h5"><a class="selflink" id="section-5.5.2.1" href="#section-5.5.2.1">5.5.2.1</a>.  Data Handling</span>

   There exist various kinds of scheduling strategies with various
   implementations.  As a base LFB library, this document only defines a
   preliminary generic scheduler LFB for abstracting a simple scheduling
   process.  Users may use this LFB as a basic LFB to further construct
   more complex scheduler LFBs by means of "inheritance", as described
   in [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>].

   Packets of any arbitrary frame type are received via a group input
   known as "PktsIn" with no additional metadata expected.  This group
   input is capable of multiple input port instances.  Each port
   instance may be connected to a different upstream LFB output.  Inside
   the LFB, it is abstracted that each input port instance is connected
   to a queue, and the queue is marked with a queue ID whose value is
   exactly the same as the index of corresponding group input port
   instance.  Scheduling disciplines are applied to all queues and also
   all packets in the queues.  The group input port property
   PortGroupLimits in ObjectLFB, as defined by the ForCES FE model
   [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>], provides means for the CE to query the capability of total
   queue numbers the scheduler supports.  The CE can then decide how
   many queues it may use for a scheduling application.

   Scheduled packets are output from a singleton output port of the LFB
   knows as "PktsOut" with no corresponding metadata.

   More complex scheduler LFBs may be defined with more complex
   scheduling disciplines by succeeding this LFB.  For instance, a
   priority scheduler LFB may be defined by inheriting this LFB and
   defining a component to indicate priorities for all input queues.

<span class="h5"><a class="selflink" id="section-5.5.2.2" href="#section-5.5.2.2">5.5.2.2</a>.  Components</span>

   The SchedulingDiscipline component is for the CE to specify a
   scheduling discipline to the LFB.  Currently defined scheduling
   disciplines only include Round Robin (RR) strategy.  The default
   scheduling discipline is thus RR.





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   The QueueStats component is defined to allow the CE to query every
   queue status of the scheduler.  It is an array component, and each
   row of the array is a struct containing a queue ID.  Currently
   defined queue status includes the queue depth in packets and the
   queue depth in bytes.  Using the queue ID as the index, the CE can
   query every queue for its used length in unit of packets or bytes.
   Note that the QueueStats component is defined as optional to
   implementers.

<span class="h5"><a class="selflink" id="section-5.5.2.3" href="#section-5.5.2.3">5.5.2.3</a>.  Capabilities</span>

   The following capability is currently defined for the
   GenericScheduler.

   o  The queue length limit providing the storage ability for every
      queue.

<span class="h5"><a class="selflink" id="section-5.5.2.4" href="#section-5.5.2.4">5.5.2.4</a>.  Events</span>

   This LFB does not have any events specified.

<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>.  XML for LFB Library</span>

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;LFBLibrary xmlns="urn:ietf:params:xml:ns:forces:lfbmodel:1.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     provides="BaseLFBLibrary"&gt;
   &lt;load library="BaseTypeLibrary"/&gt;
   &lt;LFBClassDefs&gt;
      &lt;LFBClassDef LFBClassID="3"&gt;
         &lt;name&gt;EtherPHYCop&lt;/name&gt;
         &lt;synopsis&gt;
           The EtherPHYCop LFB describes an Ethernet interface
           that limits the physical media to copper.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort&gt;
               &lt;name&gt;EtherPHYIn&lt;/name&gt;
               &lt;synopsis&gt;
                 The input port of the EtherPHYCop LFB.  It expects any
                 type of Ethernet frame.
               &lt;/synopsis&gt;
               &lt;expectation&gt;
                  &lt;frameExpected&gt;
                     &lt;ref&gt;EthernetAll&lt;/ref&gt;
                  &lt;/frameExpected&gt;
               &lt;/expectation&gt;



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            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort&gt;
               &lt;name&gt;EtherPHYOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The output port of the EtherPHYCop LFB.  The output
                 packet has the same Ethernet frame type as the
                 input packet, associated with a metadata indicating
                 the ID of the physical port.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;EthernetAll&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;PHYPortID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1" access="read-only"&gt;
               &lt;name&gt;PHYPortID&lt;/name&gt;
               &lt;synopsis&gt;
                 The identification of the physical port
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2" access="read-write"&gt;
               &lt;name&gt;AdminStatus&lt;/name&gt;
               &lt;synopsis&gt;
                 The port status administratively requested
               &lt;/synopsis&gt;
               &lt;typeRef&gt;PortStatusType&lt;/typeRef&gt;
               &lt;defaultValue&gt;2&lt;/defaultValue&gt;
            &lt;/component&gt;
            &lt;component componentID="3" access="read-only"&gt;
               &lt;name&gt;OperStatus&lt;/name&gt;
               &lt;synopsis&gt;
                 The port actual operational status
               &lt;/synopsis&gt;
               &lt;typeRef&gt;PortStatusType&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="4" access="read-write"&gt;
               &lt;name&gt;AdminLinkSpeed&lt;/name&gt;
               &lt;synopsis&gt;
                 The port link speed administratively requested



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               &lt;/synopsis&gt;
               &lt;typeRef&gt;LANSpeedType&lt;/typeRef&gt;
               &lt;defaultValue&gt;LAN_SPEED_AUTO&lt;/defaultValue&gt;
            &lt;/component&gt;
            &lt;component componentID="5" access="read-only"&gt;
               &lt;name&gt;OperLinkSpeed&lt;/name&gt;
               &lt;synopsis&gt;
                 The port actual operational link speed
               &lt;/synopsis&gt;
               &lt;typeRef&gt;LANSpeedType&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="6" access="read-write"&gt;
               &lt;name&gt;AdminDuplexMode&lt;/name&gt;
               &lt;synopsis&gt;
                 The port duplex mode administratively requested
               &lt;/synopsis&gt;
               &lt;typeRef&gt;DuplexType&lt;/typeRef&gt;
               &lt;defaultValue&gt;Auto&lt;/defaultValue&gt;
            &lt;/component&gt;
            &lt;component componentID="7" access="read-only"&gt;
               &lt;name&gt;OperDuplexMode&lt;/name&gt;
               &lt;synopsis&gt;
                 The port actual operational duplex mode
               &lt;/synopsis&gt;
               &lt;typeRef&gt;DuplexType&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="8" access="read-only"&gt;
               &lt;name&gt;CarrierStatus&lt;/name&gt;
               &lt;synopsis&gt;The carrier status of the port &lt;/synopsis&gt;
               &lt;typeRef&gt;boolean&lt;/typeRef&gt;
               &lt;defaultValue&gt;false&lt;/defaultValue&gt;
            &lt;/component&gt;
         &lt;/components&gt;
         &lt;capabilities&gt;
            &lt;capability componentID="30"&gt;
               &lt;name&gt;SupportedLinkSpeed&lt;/name&gt;
               &lt;synopsis&gt;
                 A list of link speeds the port supports
               &lt;/synopsis&gt;
               &lt;array&gt;
                  &lt;typeRef&gt;LANSpeedType&lt;/typeRef&gt;
               &lt;/array&gt;
            &lt;/capability&gt;
            &lt;capability componentID="31"&gt;
               &lt;name&gt;SupportedDuplexMode&lt;/name&gt;
               &lt;synopsis&gt;
                 A list of duplex modes the port supports
               &lt;/synopsis&gt;



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               &lt;array&gt;
                  &lt;typeRef&gt;DuplexType&lt;/typeRef&gt;
               &lt;/array&gt;
            &lt;/capability&gt;
         &lt;/capabilities&gt;
         &lt;events baseID="60"&gt;
            &lt;event eventID="1"&gt;
               &lt;name&gt;PHYPortStatusChanged&lt;/name&gt;
               &lt;synopsis&gt;
                 An event reporting change on operational status of the
                 physical port.
               &lt;/synopsis&gt;
               &lt;eventTarget&gt;
                  &lt;eventField&gt;OperStatus&lt;/eventField&gt;
               &lt;/eventTarget&gt;
               &lt;eventChanged/&gt;
               &lt;eventReports&gt;
                  &lt;eventReport&gt;
                     &lt;eventField&gt;OperStatus&lt;/eventField&gt;
                  &lt;/eventReport&gt;
               &lt;/eventReports&gt;
            &lt;/event&gt;
            &lt;event eventID="2"&gt;
               &lt;name&gt;LinkSpeedChanged&lt;/name&gt;
               &lt;synopsis&gt;
                 An event reporting change on operational link speed
                 of the physical port.
               &lt;/synopsis&gt;
               &lt;eventTarget&gt;
                  &lt;eventField&gt;OperLinkSpeed&lt;/eventField&gt;
               &lt;/eventTarget&gt;
               &lt;eventChanged/&gt;
               &lt;eventReports&gt;
                  &lt;eventReport&gt;
                     &lt;eventField&gt;OperLinkSpeed&lt;/eventField&gt;
                  &lt;/eventReport&gt;
               &lt;/eventReports&gt;
            &lt;/event&gt;
            &lt;event eventID="3"&gt;
               &lt;name&gt;DuplexModeChanged&lt;/name&gt;
               &lt;synopsis&gt;
                 An event reporting change on operational duplex mode
                 of the physical port.
               &lt;/synopsis&gt;
               &lt;eventTarget&gt;
                  &lt;eventField&gt;OperDuplexMode&lt;/eventField&gt;
               &lt;/eventTarget&gt;
               &lt;eventChanged/&gt;



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               &lt;eventReports&gt;
                  &lt;eventReport&gt;
                     &lt;eventField&gt;OperDuplexMode&lt;/eventField&gt;
                  &lt;/eventReport&gt;
               &lt;/eventReports&gt;
            &lt;/event&gt;
         &lt;/events&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="4"&gt;
         &lt;name&gt;EtherMACIn&lt;/name&gt;
         &lt;synopsis&gt;
           EtherMACIn LFB describes an Ethernet port at MAC data link
           layer.  The LFB describes Ethernet processing functions
           of MAC address locality check, deciding if the Ethernet
           packets should be bridged, providing Ethernet-layer flow
           control, etc.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort group="false"&gt;
               &lt;name&gt;EtherPktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 The input port of the EtherMACIn LFB.  It expects any
                 type of Ethernet frame.
               &lt;/synopsis&gt;
               &lt;expectation&gt;
                  &lt;frameExpected&gt;
                     &lt;ref&gt;EthernetAll&lt;/ref&gt;
                  &lt;/frameExpected&gt;
                  &lt;metadataExpected&gt;
                     &lt;ref&gt;PHYPortID&lt;/ref&gt;
                  &lt;/metadataExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;NormalPathOut&lt;/name&gt;
               &lt;synopsis&gt;
                 An output port in the EtherMACIn LFB.  It outputs
                 Ethernet packets to downstream LFBs for normal
                 processing like Ethernet packet classification and
                 other L3 IP-layer processing.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;EthernetAll&lt;/ref&gt;
                  &lt;/frameProduced&gt;



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                  &lt;metadataProduced&gt;
                     &lt;ref&gt;PHYPortID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort&gt;
               &lt;name&gt;L2BridgingPathOut&lt;/name&gt;
               &lt;synopsis&gt;
                 An output port in
                 the EtherMACIn LFB.  It outputs Ethernet packets
                 to downstream LFBs for layer 2 bridging processing.
                 The port is switched on or off by the
                 L2BridgingPathEnable flag in the LFB.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;EthernetAll&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;PHYPortID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1" access="read-write"&gt;
               &lt;name&gt;AdminStatus&lt;/name&gt;
               &lt;synopsis&gt;
                  The LFB status administratively requested, which has
                  the same data type with a port status.  Default is in
                  'Down' status.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;PortStatusType&lt;/typeRef&gt;
               &lt;defaultValue&gt;2&lt;/defaultValue&gt;
            &lt;/component&gt;
            &lt;component componentID="2" access="read-write"&gt;
               &lt;name&gt;LocalMACAddresses&lt;/name&gt;
               &lt;synopsis&gt;
                 Local MAC address(es) of the Ethernet port the LFB
                 represents.
               &lt;/synopsis&gt;
               &lt;array&gt;
                  &lt;typeRef&gt;IEEEMAC&lt;/typeRef&gt;
               &lt;/array&gt;
            &lt;/component&gt;
            &lt;component componentID="3" access="read-write"&gt;
               &lt;name&gt;L2BridgingPathEnable&lt;/name&gt;
               &lt;synopsis&gt;



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                 A flag indicating if the LFB L2 BridgingPath output
                 port is enabled or not.  Default is not enabled.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;boolean&lt;/typeRef&gt;
               &lt;defaultValue&gt;false&lt;/defaultValue&gt;
            &lt;/component&gt;
            &lt;component componentID="4" access="read-write"&gt;
               &lt;name&gt;PromiscuousMode&lt;/name&gt;
               &lt;synopsis&gt;
                 A flag indicating whether the LFB is in promiscuous
                 mode or not.  Default is not.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;boolean&lt;/typeRef&gt;
               &lt;defaultValue&gt;false&lt;/defaultValue&gt;
            &lt;/component&gt;
            &lt;component componentID="5" access="read-write"&gt;
               &lt;name&gt;TxFlowControl&lt;/name&gt;
               &lt;synopsis&gt;
                 A flag indicating whether transmit flow control is
                 applied or not.  Default is not.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;boolean&lt;/typeRef&gt;
               &lt;defaultValue&gt;false&lt;/defaultValue&gt;
            &lt;/component&gt;
            &lt;component componentID="6" access="read-write"&gt;
               &lt;name&gt;RxFlowControl&lt;/name&gt;
               &lt;synopsis&gt;
                 A flag indicating whether receive flow control is
                 applied or not.  Default is not.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;boolean&lt;/typeRef&gt;
               &lt;defaultValue&gt;false&lt;/defaultValue&gt;
            &lt;/component&gt;
            &lt;component componentID="7" access="read-reset"&gt;
               &lt;name&gt;MACInStats&lt;/name&gt;
               &lt;synopsis&gt;
                 The statistics of the EtherMACIn LFB
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;MACInStatsType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="5"&gt;
         &lt;name&gt;EtherClassifier&lt;/name&gt;
         &lt;synopsis&gt;



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           EtherClassifier LFB describes the process to decapsulate
           Ethernet packets and then classify them into various
           network-layer packets according to information in the
           Ethernet headers.  It is expected the LFB classifies packets
           by packet types like IPv4, IPv6, MPLS, ARP, ND, etc.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort&gt;
               &lt;name&gt;EtherPktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 Input port of Ethernet packets.  PHYPortID metadata is
                 always expected while LogicalPortID metadata is
                 optionally expected to associate with every input
                 Ethernet packet.
               &lt;/synopsis&gt;
               &lt;expectation&gt;
                  &lt;frameExpected&gt;
                     &lt;ref&gt;EthernetAll&lt;/ref&gt;
                  &lt;/frameExpected&gt;
                  &lt;metadataExpected&gt;
                     &lt;ref&gt;PHYPortID&lt;/ref&gt;
                     &lt;ref dependency="optional" defaultValue="0"&gt;
                  LogicalPortID&lt;/ref&gt;
                  &lt;/metadataExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort group="true"&gt;
               &lt;name&gt;ClassifyOut&lt;/name&gt;
               &lt;synopsis&gt;
                 A group port for output of Ethernet classifying
                 results.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;PHYPortID&lt;/ref&gt;
                     &lt;ref&gt;SrcMAC&lt;/ref&gt;
                     &lt;ref&gt;DstMAC&lt;/ref&gt;
                     &lt;ref&gt;EtherType&lt;/ref&gt;
                     &lt;ref availability="conditional"&gt;VlanID&lt;/ref&gt;
                     &lt;ref availability="conditional"&gt;VlanPriority&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;



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            &lt;/outputPort&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;ExceptionOut&lt;/name&gt;
               &lt;synopsis&gt;
                 A singleton port for output of all Ethernet packets
                 that fail the classifying process.  An ExceptionID
                 metadata indicates the failure reason.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ExceptionID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component access="read-write" componentID="1"&gt;
               &lt;name&gt;EtherDispatchTable&lt;/name&gt;
               &lt;synopsis&gt;
                 An EtherDispatchTable array component that is defined
                 in the LFB to dispatch every Ethernet packet to output
                 ports according to logical port ID assigned by the
                 VlanInputTable in the LFB and Ethernet type in the
                 Ethernet packet header.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;EtherDispatchTableType&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component access="read-write" componentID="2"&gt;
               &lt;name&gt;VlanInputTable&lt;/name&gt;
               &lt;synopsis&gt;
                 A VlanInputTable array component that is defined in
                 the LFB to classify VLAN Ethernet packets.  Every input
                 packet is assigned with a new LogicalPortID according
                 to the packet's incoming port ID and VLAN ID.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;VlanInputTableType&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component access="read-reset" componentID="3"&gt;
               &lt;name&gt;EtherClassifyStats&lt;/name&gt;
               &lt;synopsis&gt;
                 A table recording statistics on the Ethernet
                 classifying process in the LFB.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;EtherClassifyStatsTableType&lt;/typeRef&gt;



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            &lt;/component&gt;
         &lt;/components&gt;
       &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="6"&gt;
         &lt;name&gt;EtherEncap&lt;/name&gt;
         &lt;synopsis&gt;
           The EtherEncap LFB abstracts the process of encapsulating
           Ethernet headers onto received packets.  The encapsulation
           is based on passed metadata.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort group="false"&gt;
               &lt;name&gt;EncapIn&lt;/name&gt;
               &lt;synopsis&gt;
                 An input port receiving IPv4 and/or IPv6 packets for
                 encapsulation.  A MediaEncapInfoIndex metadata is
                 expected, and a VLAN priority metadata is optionally
                 expected with every input packet.
               &lt;/synopsis&gt;
               &lt;expectation&gt;
               &lt;frameExpected&gt;
                  &lt;ref&gt;IPv4&lt;/ref&gt;
                  &lt;ref&gt;IPv6&lt;/ref&gt;
               &lt;/frameExpected&gt;
               &lt;metadataExpected&gt;
                  &lt;ref&gt;MediaEncapInfoIndex&lt;/ref&gt;
                  &lt;ref dependency="optional" defaultValue="0"&gt;
                  VlanPriority&lt;/ref&gt;
               &lt;/metadataExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;SuccessOut&lt;/name&gt;
               &lt;synopsis&gt;
                 An output port for packets that have found Ethernet
                 L2 information and have been successfully encapsulated
                 into an Ethernet packet.  An L2PortID metadata is
                 produced for every output packet.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4&lt;/ref&gt;
                     &lt;ref&gt;IPv6&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;



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                     &lt;ref&gt;L2PortID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;ExceptionOut&lt;/name&gt;
               &lt;synopsis&gt;
                 An output port for packets that fail encapsulation
                 in the LFB.  An ExceptionID metadata indicates failure
                 reason.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4&lt;/ref&gt;
                     &lt;ref&gt;IPv6&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ExceptionID&lt;/ref&gt;
                     &lt;ref&gt;MediaEncapInfoIndex&lt;/ref&gt;
                     &lt;ref availability="conditional"&gt;VlanPriority&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1" access="read-write"&gt;
               &lt;name&gt;EncapTable&lt;/name&gt;
               &lt;synopsis&gt;
                 An array table for Ethernet encapsulation information
                 lookup.  Each row of the array contains destination MAC
                 address, source MAC address, VLAN ID, and output
                 logical L2 port ID.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;EncapTableType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="7"&gt;
         &lt;name&gt;EtherMACOut&lt;/name&gt;
         &lt;synopsis&gt;
           EtherMACOut LFB abstracts an Ethernet port at MAC data link
           layer.  It specifically describes Ethernet packet process
           for output to physical port.  A downstream LFB is usually
           an Ethernet physical LFB like EtherPHYCop LFB.  Note that
           Ethernet output functions are closely related to Ethernet
           input functions; therefore, some components defined in this
           LFB are aliases of EtherMACIn LFB components.
         &lt;/synopsis&gt;



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         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort group="false"&gt;
               &lt;name&gt;EtherPktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 The input port of the EtherMACOut LFB.  It expects
                 any type of Ethernet frame.
               &lt;/synopsis&gt;
               &lt;expectation&gt;
                  &lt;frameExpected&gt;
                     &lt;ref&gt;EthernetAll&lt;/ref&gt;
                  &lt;/frameExpected&gt;
                  &lt;metadataExpected&gt;
                     &lt;ref&gt;PHYPortID&lt;/ref&gt;
                  &lt;/metadataExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;EtherPktsOut&lt;/name&gt;
               &lt;synopsis&gt;
                 A port to output all Ethernet packets, each with a
                 metadata indicating the ID of the physical port
                 that the packet is to go through.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;EthernetAll&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;PHYPortID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1" access="read-write"&gt;
               &lt;name&gt;AdminStatus&lt;/name&gt;
               &lt;synopsis&gt;
                 The LFB status administratively requested, which has
                 the same data type with a port status.  The
                 component is defined as an alias of AdminStatus
                 component in EtherMACIn LFB.
               &lt;/synopsis&gt;
               &lt;alias&gt;PortStatusType&lt;/alias&gt;
            &lt;/component&gt;
            &lt;component componentID="2" access="read-write"&gt;



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               &lt;name&gt;MTU&lt;/name&gt;
               &lt;synopsis&gt;Maximum transmission unit (MTU) &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="3" access="read-write"&gt;
               &lt;name&gt;TxFlowControl&lt;/name&gt;
               &lt;synopsis&gt;
                 A flag indicating whether transmit flow control is
                 applied, defined as an alias of TxFlowControl
                 component in EtherMACIn LFB.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;alias&gt;boolean&lt;/alias&gt;
            &lt;/component&gt;
            &lt;component componentID="4" access="read-write"&gt;
               &lt;name&gt;RxFlowControl&lt;/name&gt;
               &lt;synopsis&gt;
                 A flag indicating whether receive flow control is
                 applied, defined as an alias of RxFlowControl
                 component in EtherMACIn LFB.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;alias&gt;boolean&lt;/alias&gt;
            &lt;/component&gt;
            &lt;component componentID="5" access="read-reset"&gt;
               &lt;name&gt;MACOutStats&lt;/name&gt;
               &lt;synopsis&gt;
                 The statistics of the EtherMACOut LFB
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;MACOutStatsType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="8"&gt;
         &lt;name&gt;IPv4Validator&lt;/name&gt;
         &lt;synopsis&gt;
          This LFB performs IPv4 validation according to <a href="./rfc1812">RFC 1812</a> and
          its updates.  The IPv4 packet will be output to the
          corresponding LFB port, indicating whether the packet is
          unicast or multicast or whether an exception has occurred
          or the validation failed.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort&gt;
               &lt;name&gt;ValidatePktsIn&lt;/name&gt;
               &lt;synopsis&gt;



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                 Input port for data packets to be validated
               &lt;/synopsis&gt;
               &lt;expectation&gt;
                  &lt;frameExpected&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort&gt;
               &lt;name&gt;IPv4UnicastOut&lt;/name&gt;
               &lt;synopsis&gt;
                 Output port for validated IPv4 unicast packets
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort&gt;
               &lt;name&gt;IPv4MulticastOut&lt;/name&gt;
               &lt;synopsis&gt;
                 Output port for validated IPv4 multicast packets
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4Multicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort&gt;
               &lt;name&gt;ExceptionOut&lt;/name&gt;
               &lt;synopsis&gt;
                 Output port for all packets with exceptional cases
                 when validating.  An ExceptionID metadata indicates
                 the exception case type.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ExceptionID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;



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            &lt;outputPort&gt;
               &lt;name&gt;FailOut&lt;/name&gt;
               &lt;synopsis&gt;
                 Output port for packets that failed validating
                 process.  A ValidateErrorID metadata indicates the
                 error type or failure reason.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ValidateErrorID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component access="read-write" componentID="1"&gt;
               &lt;name&gt;IPv4ValidatorStats&lt;/name&gt;
               &lt;synopsis&gt;
                 The statistics information for validating process in
                 the LFB.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;IPv4ValidatorStatsType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
       &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="9"&gt;
         &lt;name&gt;IPv6Validator&lt;/name&gt;
         &lt;synopsis&gt;
           This LFB performs IPv6 validation according to <a href="./rfc2460">RFC 2460</a> and
           its updates.  Then, the IPv6 packet will be output to the
           corresponding port, indicating whether the packet is
           unicast or multicast or whether an exception has occurred
           or the validation failed.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort&gt;
               &lt;name&gt;ValidatePktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 Input port for data packets to be validated
               &lt;/synopsis&gt;
               &lt;expectation&gt;
                  &lt;frameExpected&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;



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                  &lt;/frameExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort&gt;
               &lt;name&gt;IPv6UnicastOut&lt;/name&gt;
               &lt;synopsis&gt;
                 Output port for validated IPv6 unicast packets
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv6Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort&gt;
               &lt;name&gt;IPv6MulticastOut&lt;/name&gt;
               &lt;synopsis&gt;
                 Output port for validated IPv6 multicast packets
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv6Multicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort&gt;
               &lt;name&gt;ExceptionOut&lt;/name&gt;
               &lt;synopsis&gt;
                 Output port for packets with exceptional cases when
                 validating.  An ExceptionID metadata indicates the
                 exception case type.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv6&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ExceptionID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort&gt;
               &lt;name&gt;FailOut&lt;/name&gt;
               &lt;synopsis&gt;
                 Output port for packets failed validating process.
                 A ValidateErrorID metadata indicates the error type



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                 or failure reason.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv6&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ValidateErrorID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component access="read-write" componentID="1"&gt;
               &lt;name&gt;IPv6ValidatorStats&lt;/name&gt;
               &lt;synopsis&gt;
                 The statistics information for validating process in
                 the LFB.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;IPv6ValidatorStatsType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
       &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="10"&gt;
         &lt;name&gt;IPv4UcastLPM&lt;/name&gt;
         &lt;synopsis&gt;
           The IPv4UcastLPM LFB abstracts the IPv4 unicast Longest
           Prefix Match (LPM) process.  This LFB supports
           implementing equal-cost multipath (ECMP) routing and
           reverse path forwarding (RPF).
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort group="false"&gt;
               &lt;name&gt;PktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 A port for input of packets to be processed.
                 IPv4 unicast packets are expected.
               &lt;/synopsis&gt;
               &lt;expectation&gt;
               &lt;frameExpected&gt;
                  &lt;ref&gt;IPv4Unicast&lt;/ref&gt;
               &lt;/frameExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;



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            &lt;outputPort group="false"&gt;
               &lt;name&gt;NormalOut&lt;/name&gt;
               &lt;synopsis&gt;
                 An output port to output IPv4 unicast packets that
                 successfully passed the LPM lookup.  A HopSelector
                 metadata is produced to associate every output packet
                 for downstream LFB to do next-hop action.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;HopSelector&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;ECMPOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The port to output packets needing further ECMP
                 processing.  A downstream ECMP processing LFB is
                 usually followed to the port.  If ECMP is not
                 required, no downstream LFB may be connected to
                 the port.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;HopSelector&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;ExceptionOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The port to output all packets with exceptional cases
                 happened during LPM process.  An ExceptionID metadata
                 is associated to indicate what caused the exception.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ExceptionID&lt;/ref&gt;



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                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1" access="read-write"&gt;
               &lt;name&gt;IPv4PrefixTable&lt;/name&gt;
               &lt;synopsis&gt;
                 A table for IPv4 Longest Prefix Match(LPM).  The
                 destination IPv4 address of every input packet is
                 used as a search key to look up the table to find
                 out a next-hop selector.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;IPv4PrefixTableType&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2" access="read-reset"&gt;
               &lt;name&gt;IPv4UcastLPMStats&lt;/name&gt;
               &lt;synopsis&gt;
                 The statistics information for the IPv4 unicast LPM
                 process in the LFB.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;IPv4UcastLPMStatsType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="11"&gt;
         &lt;name&gt;IPv6UcastLPM&lt;/name&gt;
         &lt;synopsis&gt;
           The IPv6UcastLPM LFB abstracts the IPv6 unicast Longest
           Prefix Match (LPM) process.  This LFB supports
           implementing equal-cost multipath (ECMP) routing and
           reverse path forwarding (RPF).
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort group="false"&gt;
               &lt;name&gt;PktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 A port for input of packets to be processed.
                 IPv6 unicast packets are expected.
               &lt;/synopsis&gt;
               &lt;expectation&gt;
               &lt;frameExpected&gt;
                  &lt;ref&gt;IPv6Unicast&lt;/ref&gt;
               &lt;/frameExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;



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         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;NormalOut&lt;/name&gt;
               &lt;synopsis&gt;
                 An output port to output IPv6 unicast packets that
                 successfully passed the LPM lookup.  A HopSelector
                 metadata is produced to associate every output packet
                 for downstream LFB to do next-hop action.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv6Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;HopSelector&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;ECMPOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The port to output packets needing further ECMP
                 processing.  A downstream ECMP processing LFB is
                 usually followed to the port.  If ECMP is not
                 required, no downstream LFB may be connected to
                 the port.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv6Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;HopSelector&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;ExceptionOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The port to output all packets with exceptional cases
                 happened during LPM process.  An ExceptionID metadata
                 is associated to indicate what caused the exception.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv6Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;



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                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ExceptionID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1" access="read-write"&gt;
               &lt;name&gt;IPv6PrefixTable&lt;/name&gt;
               &lt;synopsis&gt;
                 A table for IPv6 Longest Prefix Match (LPM).  The
                 destination IPv6 address of every input packet is
                 used as a search key to look up the table to find
                 out a next-hop selector.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;IPv6PrefixTableType&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component componentID="2" access="read-reset"&gt;
               &lt;name&gt;IPv6UcastLPMStats&lt;/name&gt;
               &lt;synopsis&gt;
                The statistics information for the IPv6 unicast LPM
                process in the LFB.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;IPv6UcastLPMStatsType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="12"&gt;
         &lt;name&gt;IPv4NextHop&lt;/name&gt;
         &lt;synopsis&gt;
           The IPv4NextHop LFB abstracts the process of next-hop
           information application to IPv4 packets.  It receives an
           IPv4 packet with an associated next-hop identifier
           (HopSelector) and uses the identifier as a table index
           to look up a next-hop table to find an appropriate output
           port.  The data processing also involves the forwarding
           TTL decrement and IP checksum recalculation.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort group="false"&gt;
               &lt;name&gt;PktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 A port for input of unicast IPv4 packets, along with
                 a HopSelector metadata.
               &lt;/synopsis&gt;
               &lt;expectation&gt;



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               &lt;frameExpected&gt;
                  &lt;ref&gt;IPv4Unicast&lt;/ref&gt;
               &lt;/frameExpected&gt;
               &lt;metadataExpected&gt;
                  &lt;ref&gt;HopSelector&lt;/ref&gt;
               &lt;/metadataExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort group="true"&gt;
               &lt;name&gt;SuccessOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The group port for output of packets that
                 successfully found next-hop information.  Some
                 metadata are associated with every packet.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;L3PortID&lt;/ref&gt;
                     &lt;ref&gt;NextHopIPv4Addr&lt;/ref&gt;
                     &lt;ref availability="conditional"&gt;
                     MediaEncapInfoIndex&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;ExceptionOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The output port for packets with exceptional or
                 failure cases.  An ExceptionID metadata indicates
                 what caused the case.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv4Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ExceptionID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1"&gt;



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               &lt;name&gt;IPv4NextHopTable&lt;/name&gt;
               &lt;synopsis&gt;
                 The IPv4NextHopTable component.  A
                 HopSelector is used to match the table index
                 to find out a row that contains the next-hop
                 information result.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;IPv4NextHopTableType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="13"&gt;
         &lt;name&gt;IPv6NextHop&lt;/name&gt;
         &lt;synopsis&gt;
           The LFB abstracts the process of next-hop information
           application to IPv6 packets.  It receives an IPv6 packet
           with an associated next-hop identifier (HopSelector) and
           uses the identifier as a table index to look up a next-hop
           table to find an appropriate output port.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort group="false"&gt;
               &lt;name&gt;PktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 A port for input of unicast IPv6 packets, along with
                 a HopSelector metadata.
                &lt;/synopsis&gt;
               &lt;expectation&gt;
               &lt;frameExpected&gt;
                  &lt;ref&gt;IPv6Unicast&lt;/ref&gt;
               &lt;/frameExpected&gt;
               &lt;metadataExpected&gt;
                  &lt;ref&gt;HopSelector&lt;/ref&gt;
               &lt;/metadataExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort group="true"&gt;
               &lt;name&gt;SuccessOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The group port for output of packets that successfully
                 found next-hop information.  Some metadata are
                 associated with every packet.
                &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;



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                     &lt;ref&gt;IPv6Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;L3PortID&lt;/ref&gt;
                     &lt;ref&gt;NextHopIPv6Addr&lt;/ref&gt;
                     &lt;ref availability="conditional"&gt;
                     MediaEncapInfoIndex&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;ExceptionOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The output port for packets with exceptional or
                 failure cases.  An ExceptionID metadata indicates
                 what caused the case.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;IPv6Unicast&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ExceptionID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;IPv6NextHopTable&lt;/name&gt;
               &lt;synopsis&gt;
                 The IPv6NextHopTable component.  A HopSelector is
                 used to match the table index to find out a row that
                 contains the next-hop information result.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;IPv6NextHopTableType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="14"&gt;
         &lt;name&gt;RedirectIn&lt;/name&gt;
         &lt;synopsis&gt;
           The RedirectIn LFB abstracts the process for the ForCES CE to
           inject data packets into the ForCES FE LFBs.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;outputPorts&gt;
            &lt;outputPort group="true"&gt;



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               &lt;name&gt;PktsOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The output port of RedirectIn LFB, which is defined as
                 a group port type.  From the LFB topology's point of
                 view, the RedirectIn LFB acts as a source point for
                 data packets coming from CE; therefore, the LFB is
                 defined with a singleton output port (and no input
                 port).
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;NumPacketsReceived&lt;/name&gt;
               &lt;synopsis&gt;
                 Number of packets received from CE.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="15"&gt;
         &lt;name&gt;RedirectOut&lt;/name&gt;
         &lt;synopsis&gt;
           The RedirectOut LFB abstracts the process for LFBs in a
           ForCES FE to deliver data packets to the ForCES CE.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort group="false"&gt;
               &lt;name&gt;PktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 The input port for the RedirectOut LFB.  From the LFB
                 topology's point of view, the RedirectOut LFB acts as
                 a sink point for data packets going to the CE;
                 therefore, RedirectOut LFB is defined with a
                 singleton input port (and no output port).
               &lt;/synopsis&gt;
               &lt;expectation&gt;
                  &lt;frameExpected&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameExpected&gt;



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               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;components&gt;
            &lt;component componentID="1"&gt;
               &lt;name&gt;NumPacketsSent&lt;/name&gt;
               &lt;synopsis&gt;
                 Number of packets sent to CE.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;uint64&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
      &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="16"&gt;
         &lt;name&gt;BasicMetadataDispatch&lt;/name&gt;
         &lt;synopsis&gt;
           The BasicMetadataDispatch LFB is defined to abstract the
           process by which packets are dispatched to various output
           paths based on associated metadata value.  Current
           version of the LFB only allows the metadata value to be
           a 32-bit integer.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort&gt;
               &lt;name&gt;PktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 The packet input port for dispatching.  Every input
                 packet should be associated with a metadata that will
                 be used by the LFB to do the dispatch.
               &lt;/synopsis&gt;
               &lt;expectation&gt;
                  &lt;frameExpected&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameExpected&gt;
                  &lt;metadataExpected&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/metadataExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort group="true"&gt;
               &lt;name&gt;PktsOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The group output port that outputs dispatching
                 results.  A packet with its associated metadata



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                 having found an OutputIndex by successfully looking
                 up the dispatch table will be output to the group
                 port instance with the corresponding index.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
            &lt;outputPort group="false"&gt;
               &lt;name&gt;ExceptionOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The output port that outputs packets that failed
                 to process.  An ExceptionID metadata indicates what
                 caused the exception.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameProduced&gt;
                  &lt;metadataProduced&gt;
                     &lt;ref&gt;ExceptionID&lt;/ref&gt;
                  &lt;/metadataProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component access="read-write" componentID="1"&gt;
               &lt;name&gt;MetadataID&lt;/name&gt;
               &lt;synopsis&gt;
                 The ID of the metadata to be
                 used for dispatching packets.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/component&gt;
            &lt;component access="read-write" componentID="2"&gt;
               &lt;name&gt;MetadataDispatchTable&lt;/name&gt;
               &lt;synopsis&gt;
                 The MetadataDispatchTable component, which contains
                 entries of a metadata value and an output index,
                 specifying that a packet with the metadata value must
                 go out from the instance with the output index of the
                 LFB group output port.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;MetadataDispatchTableType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;



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       &lt;/LFBClassDef&gt;
      &lt;LFBClassDef LFBClassID="17"&gt;
         &lt;name&gt;GenericScheduler&lt;/name&gt;
         &lt;synopsis&gt;
           This is a preliminary generic scheduler LFB abstracting
           a simple scheduling process, which may be used as a
           basic LFB to construct a more complex scheduler LFB.
         &lt;/synopsis&gt;
         &lt;version&gt;1.0&lt;/version&gt;
         &lt;inputPorts&gt;
            &lt;inputPort group="true"&gt;
               &lt;name&gt;PktsIn&lt;/name&gt;
               &lt;synopsis&gt;
                 The group input port of the LFB.  Inside the LFB,
                 each instance of the group port is connected to
                 a queue marked with a queue ID, whose value is
                 index of the port instance.
               &lt;/synopsis&gt;
               &lt;expectation&gt;
                  &lt;frameExpected&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameExpected&gt;
               &lt;/expectation&gt;
            &lt;/inputPort&gt;
         &lt;/inputPorts&gt;
         &lt;outputPorts&gt;
            &lt;outputPort&gt;
               &lt;name&gt;PktsOut&lt;/name&gt;
               &lt;synopsis&gt;
                 The output port of the LFB.  Scheduled packets are
                 output from the port.
               &lt;/synopsis&gt;
               &lt;product&gt;
                  &lt;frameProduced&gt;
                     &lt;ref&gt;Arbitrary&lt;/ref&gt;
                  &lt;/frameProduced&gt;
               &lt;/product&gt;
            &lt;/outputPort&gt;
         &lt;/outputPorts&gt;
         &lt;components&gt;
            &lt;component access="read-write" componentID="1"&gt;
               &lt;name&gt;SchedulingDiscipline&lt;/name&gt;
               &lt;synopsis&gt;
                 The SchedulingDiscipline component, which is for the
                 CE to specify a scheduling discipline to the LFB.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;SchdDisciplineType&lt;/typeRef&gt;
               &lt;defaultValue&gt;1&lt;/defaultValue&gt;



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            &lt;/component&gt;
            &lt;component access="read-only" componentID="2"&gt;
               &lt;name&gt;QueueStats&lt;/name&gt;
               &lt;synopsis&gt;
                 The QueueStats component, which is defined to allow
                 the CE to query every queue statistics in the
                 scheduler.
               &lt;/synopsis&gt;
               &lt;optional/&gt;
               &lt;typeRef&gt;QueueStatsTableType&lt;/typeRef&gt;
            &lt;/component&gt;
         &lt;/components&gt;
         &lt;capabilities&gt;
            &lt;capability componentID="30"&gt;
               &lt;name&gt;QueueLenLimit&lt;/name&gt;
               &lt;synopsis&gt;
                 The QueueLenLimit capability, which specifies
                 maximum length of each queue.  The length unit is in
                 bytes.
               &lt;/synopsis&gt;
               &lt;typeRef&gt;uint32&lt;/typeRef&gt;
            &lt;/capability&gt;
         &lt;/capabilities&gt;
       &lt;/LFBClassDef&gt;
   &lt;/LFBClassDefs&gt;
&lt;/LFBLibrary&gt;

<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>.  LFB Class Use Cases</span>

   This section demonstrates examples on how the LFB classes defined by
   the base LFB library in <a href="#section-6">Section 6</a> can be applied to achieve some
   typical router functions.  The functions demonstrated are:

   o  IPv4 forwarding

   o  ARP processing

   It is assumed the LFB topology on the FE described has already been
   established by the CE and maps to the use cases illustrated in this
   section.

   The use cases demonstrated in this section are mere examples and by
   no means should be treated as the only way one would construct router
   functionality from LFBs; based on the capability of the FE(s), a CE
   should be able to express different NE applications.






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<span class="h3"><a class="selflink" id="section-7.1" href="#section-7.1">7.1</a>.  IPv4 Forwarding</span>

   Figure 2 shows the typical LFB processing path for an IPv4 unicast
   forwarding case with Ethernet media interfaces by use of the base LFB
   classes.  Note that in the figure, to focus on the IP forwarding
   function, some inputs or outputs of LFBs that are not related to the
   IPv4 forwarding function are not shown.  For example, an
   EtherClassifier LFB normally has two output ports: a "ClassifyOut"
   group output port and an "ExceptionOut" singleton output port, with
   the group port containing various port instances according to various
   classified packet types (<a href="#section-5.1.3">Section 5.1.3</a>).  In this figure, only the
   IPv4 and IPv6 packet output port instances are shown for displaying
   the mere IPv4 forwarding processing function.






































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   +-----+                +------+
   |     |                |      |
   |     |&lt;---------------|Ether |&lt;----------------------------+
   |     |                |MACOut|                             |
   |     |                |      |                             |
   |Ether|                +------+                             |
   |PHY  |                                                     |
   |Cop  |            +---+                                    |
   |#1   |  +-----+   |   |-----&gt;IPv6 Packets                  |
   |     |  |     |   |   |                                    |
   |     |  |Ether|   |   | IPv4 Packets                       |
   |     |-&gt;|MACIn|--&gt;|   |-+  +----+                          |
   +-----+  |     |   |   | |  |    |---&gt; Multicast Packets    |
            +-----+   +---+ |  |    |        +-----+  +---+    |
                      Ether +-&gt;|    |-------&gt;|     |  |   |    |
      .           Classifier|  |    |Unicast |IPv4 |  |   |    |
      .                     |  |    |Packets |Ucast|-&gt;|   |--+ |
      .                     |  +----+        |LPM  |  |   |  | |
                      +---+ |   IPv4         +-----+  +---+  | |
            +-----+   |   | |   Validator              IPv4  | |
            |     |   |   | |                         NextHop| |
   +-----+  |Ether|   |   |-+ IPv4 Packets                   | |
   |     |-&gt;|MACIn|--&gt;|   |                                  | |
   |     |  |     |   |   |-----&gt;IPv6 Packets                | |
   |Ether|  +-----+   +---+                                  | |
   |PHY  |           Ether               +----+              | |
   |Cop  |           Classifier          |    |   +-------+  | |
   |#n   |                +------+       |    |   |Ether  |  | |
   |     |                |      |       |    |&lt;--|Encap  |&lt;-+ |
   |     |                |      |&lt;------|    |   |       |    |
   |     |&lt;---------------|Ether |    ...|    |   +-------+    |
   |     |                |MACOut|   +---|    |                |
   |     |                |      |   |   +----+                |
   +-----+                +------+   | BasicMetadataDispatch   |
                                     +-----------&gt;-------------+

                Figure 2:  LFB Use Case for IPv4 Forwarding

   In the LFB use case, a number of EtherPHYCop LFB (<a href="#section-5.1.1">Section 5.1.1</a>)
   instances are used to describe physical-layer functions of the ports.
   PHYPortID metadata is generated by the EtherPHYCop LFB and is used by
   all the subsequent downstream LFBs.  An EtherMACIn LFB
   (<a href="#section-5.1.2">Section 5.1.2</a>), which describes the MAC-layer processing, follows
   every EtherPHYCop LFB.  The EtherMACIn LFB may do a locality check of
   MAC addresses if the CE configures the appropriate EtherMACIn LFB
   component.





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   Ethernet packets out of the EtherMACIn LFB are sent to an
   EtherClassifier LFB (<a href="#section-5.1.3">Section 5.1.3</a>) to be decapsulated and classified
   into network-layer types like IPv4, IPv6, ARP, etc.  In the example
   use case, every physical Ethernet interface is associated with one
   Classifier instance; although not illustrated, it is also feasible
   that all physical interfaces are associated with only one Ethernet
   Classifier instance.

   EtherClassifier uses the PHYPortID metadata, the Ethernet type of the
   input packet, and VlanID (if present in the input Ethernet packets)
   to decide the packet network-layer type and the LFB output port to
   the downstream LFB.  The EtherClassifier LFB also assigns a new
   logical port ID metadata to the packet for later use.  The
   EtherClassifier may also generate some new metadata for every packet,
   like EtherType, SrcMAC, DstMAC, LogicPortID, etc., for consumption by
   downstream LFBs.

   If a packet is classified as an IPv4 packet, it is sent downstream to
   an IPv4Validator LFB (<a href="#section-5.2.1">Section 5.2.1</a>) to validate the IPv4 packet.  In
   the validator LFB, IPv4 packets are validated and are additionally
   classified into either IPv4 unicast packets or multicast packets.
   IPv4 unicast packets are sent to downstream to the IPv4UcastLPM LFB
   (<a href="#section-5.3.1">Section 5.3.1</a>).

   The IPv4UcastLPM LFB is where the longest prefix match decision is
   made, and a next-hop selection is selected.  The next-hop ID metadata
   is generated by the IPv4UcastLPM LFB to be consumed downstream by the
   IPv4NextHop LFB (<a href="#section-5.3.2">Section 5.3.2</a>).

   The IPv4NextHop LFB uses the next-hop ID metadata to derive where the
   packet is to go next and the media encapsulation type for the port,
   etc.  The IPv4NextHop LFB generates the L3PortID metadata used to
   identify a next-hop output physical/logical port.  In the example use
   case, the next-hop output port is an Ethernet type; as a result, the
   packet and its L3 port ID metadata are sent downstream to an
   EtherEncap LFB (<a href="#section-5.1.4">Section 5.1.4</a>).

   The EtherEncap LFB encapsulates the incoming packet into an Ethernet
   frame.  A BasicMetadataDispatch LFB (<a href="#section-5.5.1">Section 5.5.1</a>) follows the
   EtherEncap LFB.  The BasicMetadataDispatch LFB is where packets are
   finally dispatched to different output physical/logical ports based
   on the L3PortID metadata sent to the LFB.









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<span class="h3"><a class="selflink" id="section-7.2" href="#section-7.2">7.2</a>.  ARP Processing</span>

   Figure 3 shows the processing path for the Address Resolution
   Protocol (ARP) in the case the CE implements the ARP processing
   function.  By no means is this the only way ARP processing could be
   achieved; as an example, ARP processing could happen at the FE, but
   that discussion is out of the scope of this use case.

          +---+                             +---+
          |   | ARP packets                 |   |
          |   |--------------&gt;---------+---&gt;|   | To CE
    ...--&gt;|   | .                      |    |   |
          |   | .                      |    +---+
          |   | .                      |   RedirectOut
          +---+                        ^
          Ether     EtherEncap         | IPv4 packets lack
        Classifier   +---+             | address resolution information
                     |   |             |
       Packets need  |   |---------&gt;---+
        ...---------&gt;|   |
     L2 Encapsulation|   |
          +---+      |   |                     +------+
          |   |  +--&gt;|   |--+   +---+          |Ether |
          |   |  |   +---+  |   |   |---------&gt;|MACOut|--&gt;...
   From CE|   |--+          +--&gt;|   | .        +------+
          |   |ARP Packets      |   | .
          |   |from CE          |   | .        +------+
          |   |                 |   |--------&gt; |Ether |--&gt;...
          +---+                 +---+          |MACOut|
       RedirectIn            BasicMetadata     +------+
                             Dispatch

                      Figure 3: LFB Use Case for ARP

   There are two ways ARP processing could be triggered in the CE as
   illustrated in Figure 3:

   o  ARP packets arriving from outside of the NE.

   o  IPV4 packets failing to resolve within the FE.

   ARP packets from network interfaces are filtered out by
   EtherClassifier LFB.  The classified ARP packets and associated
   metadata are then sent downstream to the RedirectOut LFB
   (<a href="#section-5.4.2">Section 5.4.2</a>) to be transported to CE.






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   The EtherEncap LFB, as described in <a href="#section-5.1.4">Section 5.1.4</a>, receives packets
   that need Ethernet L2 encapsulating.  When the EtherEncap LFB fails
   to find the necessary L2 Ethernet information with which to
   encapsulate the packet, it outputs the packet to its ExceptionOut LFB
   port.  Downstream to EtherEncap LFB's ExceptionOut LFB port is the
   RedirectOut LFB, which transports the packet to the CE (see
   <a href="#section-5.1.4">Section 5.1.4</a> on EtherEncap LFB for details).

   To achieve its goal, the CE needs to generate ARP request and
   response packets and send them to external (to the NE) networks.  ARP
   request and response packets from the CE are redirected to an FE via
   a RedirectIn LFB (<a href="#section-5.4.1">Section 5.4.1</a>).

   As was the case with forwarded IPv4 packets, outgoing ARP packets are
   also encapsulated to Ethernet format by the EtherEncap LFB, and then
   dispatched to different interfaces via a BasicMetadataDispatch LFB.
   The BasicMetadataDispatch LFB dispatches the packets according to the
   L3PortID metadata included in every ARP packet sent from CE.

<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>.  IANA Considerations</span>

   IANA has created a registry of ForCES LFB class names and the
   corresponding ForCES LFB class identifiers, with the location of the
   definition of the ForCES LFB class, in accordance with the rules to
   use the namespace.

   This document registers the unique class names and numeric class
   identifiers for the LFBs listed in <a href="#section-8.1">Section 8.1</a>.  Besides, this
   document defines the following namespaces:

   o  Metadata ID, defined in Sections <a href="#section-4.3">4.3</a> and <a href="#section-4.4">4.4</a>

   o  Exception ID, defined in <a href="#section-4.4">Section 4.4</a>

   o  Validate Error ID, defined in <a href="#section-4.4">Section 4.4</a>
















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<span class="grey"><a href="./rfc6956">RFC 6956</a>                   ForCES LFB Library                  June 2013</span>


<span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>.  LFB Class Names and LFB Class Identifiers</span>

   LFB classes defined by this document belong to LFBs defined by
   Standards Track RFCs.  According to IANA, the registration procedure
   is Standards Action for the range 0 to 65535 and First Come First
   Served with any publicly available specification for over 65535.

   The assignment of LFB class names and LFB class identifiers is as in
   the following table.

   +----------+--------------- +------------------------+--------------+
   |LFB Class | LFB Class Name |     Description        |  Reference   |
   |Identifier|                |                        |              |
   +----------+--------------- +------------------------+--------------+
   |    3     |  EtherPHYCop   | Define an Ethernet port|   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | abstracted at physical | <a href="#section-5.1.1">Section 5.1.1</a>|
   |          |                | layer.                 |              |
   |          |                |                        |              |
   |    4     |  EtherMACIn    | Define an Ethernet     |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | input port at MAC data | <a href="#section-5.1.2">Section 5.1.2</a>|
   |          |                | link layer.            |              |
   |          |                |                        |              |
   |    5     |EtherClassifier | Define the process to  |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | decapsulate Ethernet   | <a href="#section-5.1.3">Section 5.1.3</a>|
   |          |                | packets and classify   |              |
   |          |                | the packets.           |              |
   |          |                |                        |              |
   |    6     |  EtherEncap    | Define the process to  |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | encapsulate IP packets | <a href="#section-5.1.4">Section 5.1.4</a>|
   |          |                | to Ethernet packets.   |              |
   |          |                |                        |              |
   |    7     |  EtherMACOut   | Define an Ethernet     |   <a href="./rfc6956">RFC 6956</a>   |
   |          |                | output port at MAC     | <a href="#section-5.1.5">Section 5.1.5</a>|
   |          |                | data link layer.       |              |
   |          |                |                        |              |
   |    8     | IPv4Validator  | Perform IPv4 packets   |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | validation.            | <a href="#section-5.2.1">Section 5.2.1</a>|
   |          |                |                        |              |
   |    9     | IPv6Validator  | Perform IPv6 packets   |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | validation.            | <a href="#section-5.2.2">Section 5.2.2</a>|
   |          |                |                        |              |
   |    10    | IPv4UcastLPM   | Perform IPv4 Longest   |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | Prefix Match Lookup.   | <a href="#section-5.3.1">Section 5.3.1</a>|
   |          |                |                        |              |
   |    11    | IPv6UcastLPM   | Perform IPv6 Longest   |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | Prefix Match Lookup.   | <a href="#section-5.3.3">Section 5.3.3</a>|
   |          |                |                        |              |




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   |    12    |  IPv4NextHop   | Define the process of  |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | selecting IPv4 next-hop| <a href="#section-5.3.2">Section 5.3.2</a>|
   |          |                | action.                |              |
   |          |                |                        |              |
   |    13    |  IPv6NextHop   | Define the process of  |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | selecting IPv6 next-hop| <a href="#section-5.3.4">Section 5.3.4</a>|
   |          |                | action.                |              |
   |          |                |                        |              |
   |    14    |  RedirectIn    | Define the process for |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | CE to inject data      | <a href="#section-5.4.1">Section 5.4.1</a>|
   |          |                | packets into FE LFB    |              |
   |          |                | topology.              |              |
   |          |                |                        |              |
   |    15    |  RedirectOut   | Define the process for |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | LFBs in FE to deliver  | <a href="#section-5.4.2">Section 5.4.2</a>|
   |          |                | data packets to CE.    |              |
   |          |                |                        |              |
   |    16    | BasicMetadata  | Dispatch input packets |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |    Dispatch    | to a group output      | <a href="#section-5.5.1">Section 5.5.1</a>|
   |          |                | according to a metadata|              |
   |          |                |                        |              |
   |    17    |GenericScheduler| Define a preliminary   |   <a href="./rfc6956">RFC 6956</a>,  |
   |          |                | generic scheduling     | <a href="#section-5.5.2">Section 5.5.2</a>|
   |          |                | process.               |              |
   +----------+--------------- +------------------------+--------------+

                                 Table 1
























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<span class="grey"><a href="./rfc6956">RFC 6956</a>                   ForCES LFB Library                  June 2013</span>


<span class="h3"><a class="selflink" id="section-8.2" href="#section-8.2">8.2</a>.  Metadata ID</span>

   The Metadata ID namespace is 32 bits long.  Below are the guidelines
   for managing the namespace.

   Metadata IDs in the range of 0x00000001-0x7FFFFFFF are Specification
   Required [<a href="./rfc5226" title="">RFC5226</a>].  A metadata ID using this range MUST be
   documented in an RFC or other permanent and readily available
   reference.

   Values assigned by this specification:

   +--------------+-------------------------+--------------------------+
   |   Value      |           Name          |        Definition        |
   +--------------+-------------------------+--------------------------+
   |  0x00000000  |         Reserved        |   <a href="./rfc6956">RFC 6956</a>               |
   |  0x00000001  |       PHYPortID         |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x00000002  |         SrcMAC          |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x00000003  |         DstMAC          |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x00000004  |       LogicalPortID     |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x00000005  |         EtherType       |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x00000006  |          VlanID         |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x00000007  |       VlanPriority      |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x00000008  |       NextHopIPv4Addr   |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x00000009  |       NextHopIPv6Addr   |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x0000000A  |       HopSelector       |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x0000000B  |       ExceptionID       |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x0000000C  |      ValidateErrorID    |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x0000000D  |         L3PortID        |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x0000000E  |       RedirectIndex     |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x0000000F  |    MediaEncapInfoIndex  |   <a href="./rfc6956#section-4.4">RFC 6956, Section&nbsp;4.4</a>  |
   |  0x80000000- |      Reserved for       |   <a href="./rfc6956">RFC 6956</a>               |
   |  0xFFFFFFFF  |      Private Use        |                          |
   +--------------+-------------------------+--------------------------+

                                   Table 2















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<span class="grey"><a href="./rfc6956">RFC 6956</a>                   ForCES LFB Library                  June 2013</span>


<span class="h3"><a class="selflink" id="section-8.3" href="#section-8.3">8.3</a>.  Exception ID</span>

   The Exception ID namespace is 32 bits long.  Below are the guidelines
   for managing the namespace.

   Exception IDs in the range of 0x00000000-0x7FFFFFFF are Specification
   Required [<a href="./rfc5226" title="">RFC5226</a>].  An exception ID using this range MUST be
   documented in an RFC or other permanent and readily available
   reference.

   Values assigned by this specification:

   +--------------+---------------------------------+------------------+
   |   Value      |           Name                  |   Definition     |
   +--------------+---------------------------------+------------------+
   |  0x00000000  |  AnyUnrecognizedExceptionCase   | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000001  |        ClassifyNoMatching       | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000002  |   MediaEncapInfoIndexInvalid    | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000003  |       EncapTableLookupFailed    | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000004  |             BadTTL              | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000005  |     IPv4HeaderLengthMismatch    | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000006  |        RouterAlertOptions       | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000007  |         IPv6HopLimitZero        | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000008  |       IPv6NextHeaderHBH         | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000009  |      SrcAddressException        | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x0000000A  |      DstAddressException        | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x0000000B  |        LPMLookupFailed          | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x0000000C  |       HopSelectorInvalid        | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x0000000D  |      NextHopLookupFailed        | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x0000000E  |          FragRequired           | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x0000000F  |       MetadataNoMatching        | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x80000000- |         Reserved for            | <a href="./rfc6956">RFC 6956</a>         |
   |  0xFFFFFFFF  |         Private Use             |                  |
   +--------------+---------------------------------+------------------+

                                  Table 3















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<span class="h3"><a class="selflink" id="section-8.4" href="#section-8.4">8.4</a>.  Validate Error ID</span>

   The Validate Error ID namespace is 32 bits long.  Below are the
   guidelines for managing the namespace.

   Validate Error IDs in the range of 0x00000000-0x7FFFFFFF are
   Specification Required [<a href="./rfc5226" title="">RFC5226</a>].  A Validate Error ID using this
   range MUST be documented in an RFC or other permanent and readily
   available reference.

   Values assigned by this specification:

   +--------------+---------------------------------+------------------+
   |   Value      |           Name                  |   Definition     |
   +--------------+---------------------------------+------------------+
   |  0x00000000  | AnyUnrecognizedValidateErrorCase| See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000001  |        InvalidIPv4PacketSize    | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000002  |           NotIPv4Packet         | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000003  |    InvalidIPv4HeaderLengthSize  | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000004  |    InvalidIPv4LengthFieldSize   | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000005  |         InvalidIPv4Checksum     | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000006  |      InvalidIPv4SrcAddr         | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000007  |      InvalidIPv4DstAddr         | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000008  |      InvalidIPv6PacketSize      | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x00000009  |          NotIPv6Packet          | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x0000000A  |      InvalidIPv6SrcAddr         | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x0000000B  |      InvalidIPv6DstAddr         | See <a href="#section-4.4">Section 4.4</a>  |
   |  0x80000000- |        Reserved for             | <a href="./rfc6956">RFC 6956</a>         |
   |  0xFFFFFFFF  |        Private Use              |                  |
   +--------------+---------------------------------+------------------+

                                   Table 4



















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<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>.  Security Considerations</span>

   The ForCES framework document [<a href="./rfc3746" title="&quot;Forwarding and Control Element Separation (ForCES) Framework&quot;">RFC3746</a>] provides a description of the
   security needs for the overall ForCES architecture.  For example, the
   ForCES protocol entities must be authenticated per the ForCES
   requirements before they can access the information elements
   described in this document via ForCES.  The ForCES protocol document
   [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>] includes a comprehensive set of security mechanisms that
   implementations are required to support to meet these needs.  SCTP-
   based Transport Mapping Layer (TML) for the ForCES protocol [<a href="./rfc5811" title="&quot;SCTP-Based Transport Mapping Layer (TML) for the Forwarding and Control Element Separation (ForCES) Protocol&quot;">RFC5811</a>]
   specifies security mechanisms for transport mapping for the ForCES
   protocol.  The LFBs defined in this document are similar to other
   LFBs modeled by the FE model [<a href="./rfc5812" title="&quot;Forwarding and Control Element Separation (ForCES) Forwarding Element Model&quot;">RFC5812</a>].  In particular, they have the
   same security properties.  Thus, the security mechanisms and
   considerations from the ForCES protocol document [<a href="./rfc5810" title="&quot;Forwarding and Control Element Separation (ForCES) Protocol Specification&quot;">RFC5810</a>] apply to
   this document.

<span class="h2"><a class="selflink" id="section-10" href="#section-10">10</a>.  References</span>

<span class="h3"><a class="selflink" id="section-10.1" href="#section-10.1">10.1</a>.  Normative References</span>

   [<a id="ref-RFC2119">RFC2119</a>]      Bradner, S., "Key words for use in RFCs to Indicate
                  Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>, March 1997.

   [<a id="ref-RFC5810">RFC5810</a>]      Doria, A., Hadi Salim, J., Haas, R., Khosravi, H.,
                  Wang, W., Dong, L., Gopal, R., and J. Halpern,
                  "Forwarding and Control Element Separation (ForCES)
                  Protocol Specification", <a href="./rfc5810">RFC 5810</a>, March 2010.

   [<a id="ref-RFC5811">RFC5811</a>]      Hadi Salim, J. and K. Ogawa, "SCTP-Based Transport
                  Mapping Layer (TML) for the Forwarding and Control
                  Element Separation (ForCES) Protocol", <a href="./rfc5811">RFC 5811</a>,
                  March 2010.

   [<a id="ref-RFC5812">RFC5812</a>]      Halpern, J. and J. Hadi Salim, "Forwarding and Control
                  Element Separation (ForCES) Forwarding Element Model",
                  <a href="./rfc5812">RFC 5812</a>, March 2010.

<span class="h3"><a class="selflink" id="section-10.2" href="#section-10.2">10.2</a>.  Informative References</span>

   [<a id="ref-IEEE.802-1Q">IEEE.802-1Q</a>]  IEEE, "IEEE Standard for Local and metropolitan area
                  networks -- Media Access Control (MAC) Bridges and
                  Virtual Bridged Local Area Networks", IEEE Standard
                  802.1Q, 2011.

   [<a id="ref-RFC1122">RFC1122</a>]      Braden, R., "Requirements for Internet Hosts -
                  Communication Layers", STD 3, <a href="./rfc1122">RFC 1122</a>, October 1989.




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   [<a id="ref-RFC1812">RFC1812</a>]      Baker, F., "Requirements for IP Version 4 Routers",
                  <a href="./rfc1812">RFC 1812</a>, June 1995.

   [<a id="ref-RFC2460">RFC2460</a>]      Deering, S. and R. Hinden, "Internet Protocol, Version
                  6 (IPv6) Specification", <a href="./rfc2460">RFC 2460</a>, December 1998.

   [<a id="ref-RFC2578">RFC2578</a>]      McCloghrie, K., Ed., Perkins, D., Ed., and J.
                  Schoenwaelder, Ed., "Structure of Management
                  Information Version 2 (SMIv2)", STD 58, <a href="./rfc2578">RFC 2578</a>,
                  April 1999.

   [<a id="ref-RFC3746">RFC3746</a>]      Yang, L., Dantu, R., Anderson, T., and R. Gopal,
                  "Forwarding and Control Element Separation (ForCES)
                  Framework", <a href="./rfc3746">RFC 3746</a>, April 2004.

   [<a id="ref-RFC5226">RFC5226</a>]      Narten, T. and H. Alvestrand, "Guidelines for Writing
                  an IANA Considerations Section in RFCs", <a href="https://www.rfc-editor.org/bcp/bcp26">BCP 26</a>,
                  <a href="./rfc5226">RFC 5226</a>, May 2008.

































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<span class="h2"><a class="selflink" id="appendix-A" href="#appendix-A">Appendix A</a>.  Acknowledgements</span>

   The authors would like to acknowledge the following people, whose
   input was particularly helpful during development of this document:

      Edward Crabbe
      Adrian Farrel
      Rong Jin
      Bin Zhuge
      Ming Gao
      Jingjing Zhou
      Xiaochun Wu
      Derek Atkins
      Stephen Farrell
      Meral Shirazipour
      Jari Arkko
      Martin Stiemerling
      Stewart Bryant
      Richard Barnes

<span class="h2"><a class="selflink" id="appendix-B" href="#appendix-B">Appendix B</a>.  Contributors</span>

   The authors would like to thank Jamal Hadi Salim, Ligang Dong, and
   Fenggen Jia, all of whom made major contributions to the development
   of this document.  Ligang Dong and Fenggen Jia were also two of the
   authors of earlier documents from which this document evolved.

   Jamal Hadi Salim
   Mojatatu Networks
   Ottawa, Ontario
   Canada
   EMail: hadi@mojatatu.com

   Ligang Dong
   Zhejiang Gongshang University
   18 Xuezheng Str., Xiasha University Town
   Hangzhou 310018
   P.R. China
   EMail: donglg@zjsu.edu.cn

   Fenggen Jia
   National Digital Switching Center (NDSC)
   Jianxue Road
   Zhengzhou 452000
   P.R. China
   EMail: jfg@mail.ndsc.com.cn





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Authors' Addresses

   Weiming Wang
   Zhejiang Gongshang University
   18 Xuezheng Str., Xiasha University Town
   Hangzhou  310018
   P.R. China

   Phone: +86 571 28877751
   EMail: wmwang@zjsu.edu.cn


   Evangelos Haleplidis
   University of Patras
   Department of Electrical &amp; Computer Engineering
   Patras  26500
   Greece

   EMail: ehalep@ece.upatras.gr


   Kentaro Ogawa
   NTT Corporation
   Tokyo
   Japan

   EMail: ogawa.kentaro@lab.ntt.co.jp


   Chuanhuang Li
   Hangzhou DPtech
   6th Floor, Zhongcai Group, 68 Tonghe Road, Binjiang District
   Hangzhou  310051
   P.R. China

   EMail: chuanhuang_li@zjsu.edu.cn


   Joel Halpern
   Ericsson
   P.O. Box 6049
   Leesburg, VA  20178
   USA

   Phone: +1 703 371 3043
   EMail: joel.halpern@ericsson.com





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</pre>