<pre>Network Working Group                                  L. Berger, Editor
Request for Comments: 3471                                Movaz Networks
Category: Standards Track                                   January 2003


           <span class="h1">Generalized Multi-Protocol Label Switching (GMPLS)</span>
                    <span class="h1">Signaling Functional Description</span>

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   This document describes extensions to Multi-Protocol Label Switching
   (MPLS) signaling required to support Generalized MPLS.  Generalized
   MPLS extends the MPLS control plane to encompass time-division (e.g.,
   Synchronous Optical Network and Synchronous Digital Hierarchy,
   SONET/SDH), wavelength (optical lambdas) and spatial switching (e.g.,
   incoming port or fiber to outgoing port or fiber).  This document
   presents a functional description of the extensions.  Protocol
   specific formats and mechanisms, and technology specific details are
   specified in separate documents.

Table of Contents

   <a href="#section-1">1</a>.  Introduction  ...............................................   <a href="#page-2">2</a>
   <a href="#section-2">2</a>.  Overview   ..................................................   <a href="#page-3">3</a>
   <a href="#section-3">3</a>.  Label Related Formats   .....................................   <a href="#page-6">6</a>
     <a href="#section-3.1">3.1</a>  Generalized Label Request  ...............................   <a href="#page-6">6</a>
     <a href="#section-3.2">3.2</a>  Generalized Label  .......................................  <a href="#page-11">11</a>
     <a href="#section-3.3">3.3</a>  Waveband Switching  ......................................  <a href="#page-12">12</a>
     <a href="#section-3.4">3.4</a>  Suggested Label  .........................................  <a href="#page-13">13</a>
     <a href="#section-3.5">3.5</a>  Label Set  ...............................................  <a href="#page-14">14</a>
   <a href="#section-4">4</a>.  Bidirectional LSPs  .........................................  <a href="#page-16">16</a>
     <a href="#section-4.1">4.1</a>  Required Information  ....................................  <a href="#page-17">17</a>
     <a href="#section-4.2">4.2</a>  Contention Resolution  ...................................  <a href="#page-17">17</a>
   <a href="#section-5">5</a>.  Notification on Label Error  ................................  <a href="#page-20">20</a>
   <a href="#section-6">6</a>.  Explicit Label Control  .....................................  <a href="#page-20">20</a>
     <a href="#section-6.1">6.1</a>  Required Information  ....................................  <a href="#page-21">21</a>



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   <a href="#section-7">7</a>.  Protection Information  .....................................  <a href="#page-21">21</a>
     <a href="#section-7.1">7.1</a>  Required Information  ....................................  <a href="#page-22">22</a>
   <a href="#section-8">8</a>.  Administrative Status Information  ..........................  <a href="#page-23">23</a>
     <a href="#section-8.1">8.1</a>  Required Information  ....................................  <a href="#page-24">24</a>
   <a href="#section-9">9</a>.  Control Channel Separation  .................................  <a href="#page-25">25</a>
     <a href="#section-9.1">9.1</a>  Interface Identification  ................................  <a href="#page-25">25</a>
     <a href="#section-9.2">9.2</a>  Fault Handling  ..........................................  <a href="#page-27">27</a>
   <a href="#section-10">10</a>. Acknowledgments  ............................................  <a href="#page-27">27</a>
   <a href="#section-11">11</a>. Security Considerations  ....................................  <a href="#page-28">28</a>
   <a href="#section-12">12</a>. IANA Considerations  ........................................  <a href="#page-28">28</a>
   <a href="#section-13">13</a>. Intellectual Property Considerations  .......................  <a href="#page-29">29</a>
   <a href="#section-14">14</a>. References  .................................................  <a href="#page-29">29</a>
     <a href="#section-14.1">14.1</a>  Normative References  ...................................  <a href="#page-29">29</a>
     <a href="#section-14.2">14.2</a>  Informative References  .................................  <a href="#page-30">30</a>
   <a href="#section-15">15</a>. Contributors  ...............................................  <a href="#page-31">31</a>
   <a href="#section-16">16</a>. Editor's Address  ...........................................  <a href="#page-33">33</a>
   <a href="#section-17">17</a>. Full Copyright Statement  ...................................  <a href="#page-34">34</a>

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

   The Multiprotocol Label Switching (MPLS) architecture [<a href="./rfc3031" title="&quot;Multiprotocol label switching Architecture&quot;">RFC3031</a>] has
   been defined to support the forwarding of data based on a label.  In
   this architecture, Label Switching Routers (LSRs) were assumed to
   have a forwarding plane that is capable of (a) recognizing either
   packet or cell boundaries, and (b) being able to process either
   packet headers (for LSRs capable of recognizing packet boundaries) or
   cell headers (for LSRs capable of recognizing cell boundaries).

   The original architecture has recently been extended to include LSRs
   whose forwarding plane recognizes neither packet, nor cell
   boundaries, and therefore, can't forward data based on the
   information carried in either packet or cell headers.  Specifically,
   such LSRs include devices where the forwarding decision is based on
   time slots, wavelengths, or physical ports.

   Given the above, LSRs, or more precisely interfaces on LSRs, can be
   subdivided into the following classes:

   1. Interfaces that recognize packet/cell boundaries and can forward
      data based on the content of the packet/cell header.  Examples
      include interfaces on routers that forward data based on the
      content of the "shim" header, interfaces on (Asynchronous Transfer
      Mode) ATM-LSRs that forward data based on the ATM VPI/VCI.  Such
      interfaces are referred to as Packet-Switch Capable (PSC).







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   2. Interfaces that forward data based on the data's time slot in a
      repeating cycle.  An example of such an interface is an interface
      on a SONET/SDH Cross-Connect.  Such interfaces are referred to as
      Time-Division Multiplex Capable (TDM).

   3. Interfaces that forward data based on the wavelength on which the
      data is received.  An example of such an interface is an interface
      on an Optical Cross-Connect that can operate at the level of an
      individual wavelength.  Such interfaces are referred to as Lambda
      Switch Capable (LSC).

   4. Interfaces that forward data based on a position of the data in
      the real world physical spaces.  An example of such an interface
      is an interface on an Optical Cross-Connect that can operate at
      the level of a single (or multiple) fibers.  Such interfaces are
      referred to as Fiber-Switch Capable (FSC).

   Using the concept of nested Label Switched Paths (LSPs) allows the
   system to scale by building a forwarding hierarchy.  At the top of
   this hierarchy are FSC interfaces, followed by LSC interfaces,
   followed by TDM interfaces, followed by PSC interfaces.  This way, an
   LSP that starts and ends on a PSC interface can be nested (together
   with other LSPs) into an LSP that starts and ends on a TDM interface.
   This LSP, in turn, can be nested (together with other LSPs) into an
   LSP that starts and ends on an LSC interface, which in turn can be
   nested (together with other LSPs) into an LSP that starts and ends on
   a FSC interface.  See [<a href="#ref-MPLS-HIERARCHY" title="&quot;LSP Hierarchy with MPLS TE&quot;">MPLS-HIERARCHY</a>] for more information on LSP
   hierarchies.

   The establishment of LSPs that span only the first class of
   interfaces is defined in [RFC3036, <a href="./rfc3212">RFC3212</a>, <a href="./rfc3209">RFC3209</a>].  This document
   presents a functional description of the extensions needed to
   generalize the MPLS control plane to support each of the four classes
   of interfaces.  Only signaling protocol independent formats and
   definitions are provided in this document.  Protocol specific formats
   are defined in [<a href="./rfc3473" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions&quot;">RFC3473</a>] and [<a href="./rfc3472" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions&quot;">RFC3472</a>].  Technology specific details
   are outside the scope of this document and will be specified in
   technology specific documents, such as [<a href="#ref-GMPLS-SONET" title="&quot;GMPLS - SONET / SDH Specifics&quot;">GMPLS-SONET</a>].

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

   Generalized MPLS differs from traditional MPLS in that it supports
   multiple types of switching, i.e., the addition of support for TDM,
   lambda, and fiber (port) switching.  The support for the additional



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   types of switching has driven generalized MPLS to extend certain base
   functions of traditional MPLS and, in some cases, to add
   functionality.  These changes and additions impact basic LSP
   properties, how labels are requested and communicated, the
   unidirectional nature of LSPs, how errors are propagated, and
   information provided for synchronizing the ingress and egress.

   In traditional MPLS Traffic Engineering, links traversed by an LSP
   can include an intermix of links with heterogeneous label encodings.
   For example, an LSP may span links between routers, links between
   routers and ATM-LSRs, and links between ATM-LSRs.  Generalized MPLS
   extends this by including links where the label is encoded as a time
   slot, or a wavelength, or a position in the real world physical
   space.  Just like with traditional MPLS TE, where not all LSRs are
   capable of recognizing (IP) packet boundaries (e.g., an ATM-LSR) in
   their forwarding plane, generalized MPLS includes support for LSRs
   that can't recognize (IP) packet boundaries in their forwarding
   plane.  In traditional MPLS TE an LSP that carries IP has to start
   and end on a router.  Generalized MPLS extends this by requiring an
   LSP to start and end on similar type of LSRs.  Also, in generalized
   MPLS the type of a payload that can be carried by an LSP is extended
   to allow such payloads as SONET/SDH, or 1 or 10Gb Ethernet.  These
   changes from traditional MPLS are reflected in how labels are
   requested and communicated in generalized MPLS, see Sections <a href="#section-3.1">3.1</a> and
   3.2.  A special case of Lambda switching, called Waveband switching
   is also described in <a href="#section-3.3">Section 3.3</a>.

   Another basic difference between traditional and non-PSC types of
   generalized MPLS LSPs, is that bandwidth allocation for an LSP can be
   performed only in discrete units, see <a href="#section-3.1.3">Section 3.1.3</a>.  There are also
   likely to be (much) fewer labels on non-PSC links than on PSC links.
   Note that the use of Forwarding Adjacencies (FA), see [MPLS-
   HIERARCHY], provides a mechanism that may improve bandwidth
   utilization, when bandwidth allocation can be performed only in
   discrete units, as well as a mechanism to aggregate forwarding state,
   thus allowing the number of required labels to be reduced.

   Generalized MPLS allows for a label to be suggested by an upstream
   node, see <a href="#section-3.4">Section 3.4</a>.  This suggestion may be overridden by a
   downstream node but, in some cases, at the cost of higher LSP setup
   time.  The suggested label is valuable when establishing LSPs through
   certain kinds of optical equipment where there may be a lengthy (in
   electrical terms) delay in configuring the switching fabric.  For
   example micro mirrors may have to be elevated or moved, and this
   physical motion and subsequent damping takes time.  If the labels and
   hence switching fabric are configured in the reverse direction (the





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   norm) the MAPPING/Resv message may need to be delayed by 10's of
   milliseconds per hop in order to establish a usable forwarding path.
   The suggested label is also valuable when recovering from nodal
   faults.

   Generalized MPLS extends on the notion of restricting the range of
   labels that may be selected by a downstream node, see <a href="#section-3.5">Section 3.5</a>.
   In generalized MPLS, an ingress or other upstream node may restrict
   the labels that may be used by an LSP along either a single hop or
   along the whole LSP path.  This feature is driven from the optical
   domain where there are cases where wavelengths used by the path must
   be restricted either to a small subset of possible wavelengths, or to
   one specific wavelength.  This requirement occurs because some
   equipment may only be able to generate a small set of the wavelengths
   that intermediate equipment may be able to switch, or because
   intermediate equipment may not be able to switch a wavelength at all,
   being only able to redirect it to a different fiber.

   While traditional traffic engineered MPLS (and even LDP) are
   unidirectional, generalized MPLS supports the establishment of
   bidirectional LSPs, see <a href="#section-4">Section 4</a>.  The need for bidirectional LSPs
   comes from non-PSC applications.  There are multiple reasons why such
   LSPs are needed, particularly possible resource contention when
   allocating reciprocal LSPs via separate signaling sessions, and
   simplifying failure restoration procedures in the non-PSC case.
   Bidirectional LSPs also have the benefit of lower setup latency and
   lower number of messages required during setup.

   Generalized MPLS supports the communication of a specific label to
   use on a specific interface, see <a href="./rfc3473#section-6">Section&nbsp;6.  [RFC3473]</a> also supports
   an RSVP specific mechanism for rapid failure notification.

   Generalized MPLS formalizes possible separation of control and data
   channels, see <a href="#section-9">Section 9</a>.  Such support is particularly important to
   support technologies where control traffic cannot be sent in-band
   with the data traffic.

   Generalized MPLS also allows for the inclusion of technology specific
   parameters in signaling.  The intent is for all technology specific
   parameters to be carried, when using RSVP, in the SENDER_TSPEC and
   other related objects, and when using CR-LDP, in the Traffic
   Parameters TLV.  Technology specific formats will be defined on an as
   needed basis.  For an example definition, see [<a href="#ref-GMPLS-SONET" title="&quot;GMPLS - SONET / SDH Specifics&quot;">GMPLS-SONET</a>].








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

   To deal with the widening scope of MPLS into the optical and time
   domain, several new forms of "label" are required.  These new forms
   of label are collectively referred to as a "generalized label".  A
   generalized label contains enough information to allow the receiving
   node to program its cross connect, regardless of the type of this
   cross connect, such that the ingress segments of the path are
   properly joined.  This section defines a generalized label request, a
   generalized label, support for waveband switching, suggested label
   and label sets.

   Note that since the nodes sending and receiving the new form of label
   know what kinds of link they are using, the generalized label does
   not contain a type field, instead the nodes are expected to know from
   context what type of label to expect.

<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. Generalized Label Request</span>

   The Generalized Label Request supports communication of
   characteristics required to support the LSP being requested.  These
   characteristics include LSP encoding and LSP payload.  Note that
   these characteristics may be used by transit nodes, e.g., to support
   penultimate hop popping.

   The Generalized Label Request carries an LSP encoding parameter,
   called LSP Encoding Type.  This parameter indicates the encoding
   type, e.g., SONET/SDH/GigE etc., that will be used with the data
   associated with the LSP.  The LSP Encoding Type represents the nature
   of the LSP, and not the nature of the links that the LSP traverses.
   A link may support a set of encoding formats, where support means
   that a link is able to carry and switch a signal of one or more of
   these encoding formats depending on the resource availability and
   capacity of the link.  For example, consider an LSP signaled with
   "lambda" encoding.   It is expected that such an LSP would be
   supported with no electrical conversion and no knowledge of the
   modulation and speed by the transit nodes.  Other formats normally
   require framing knowledge, and field parameters are broken into the
   framing type and speed as shown below.

   The Generalized Label Request also indicates the type of switching
   that is being requested on a link.  This field normally is consistent
   across all links of an LSP.








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<span class="h4"><a class="selflink" id="section-3.1.1" href="#section-3.1.1">3.1.1</a>. Required Information</span>

   The information carried in a Generalized Label Request is:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | LSP Enc. Type |Switching Type |             G-PID             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      LSP Encoding Type: 8 bits

         Indicates the encoding of the LSP being requested.  The
         following shows permitted values and their meaning:

   Value       Type
   -----       ----
     1         Packet
     2         Ethernet
     3         ANSI/ETSI PDH
     4         Reserved
     5         SDH ITU-T G.707 / SONET ANSI T1.105
     6         Reserved
     7         Digital Wrapper
     8         Lambda (photonic)
     9         Fiber
    10         Reserved
    11         FiberChannel

         The ANSI PDH and ETSI PDH types designate these respective
         networking technologies.  DS1 and DS3 are examples of ANSI PDH
         LSPs.  An E1 LSP would be ETSI PDH.  The Lambda encoding type
         refers to an LSP that encompasses a whole wavelengths.  The
         Fiber encoding type refers to an LSP that encompasses a whole
         fiber port.
















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      Switching Type: 8 bits

         Indicates the type of switching that should be performed on a
         particular link.  This field is needed for links that advertise
         more than one type of switching capability.  This field should
         map to one of the values advertised for the corresponding link
         in the routing Switching Capability Descriptor, see [GMPLS-
         RTG].

         The following are currently defined values:

   Value       Type
   -----       ----
     1         Packet-Switch Capable-1 (PSC-1)
     2         Packet-Switch Capable-2 (PSC-2)
     3         Packet-Switch Capable-3 (PSC-3)
     4         Packet-Switch Capable-4 (PSC-4)
     51        Layer-2 Switch Capable  (L2SC)
     100       Time-Division-Multiplex Capable (TDM)
     150       Lambda-Switch Capable   (LSC)
     200       Fiber-Switch Capable    (FSC)






























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      Generalized PID (G-PID): 16 bits

         An identifier of the payload carried by an LSP, i.e., an
         identifier of the client layer of that LSP.  This is used by
         the nodes at the endpoints of the LSP, and in some cases by the
         penultimate hop.  Standard Ethertype values are used for packet
         and Ethernet LSPs; other values are:

   Value   Type                                   Technology
   -----   ----                                   ----------
     0     Unknown                                All
     1     Reserved
     2     Reserved
     3     Reserved
     4     Reserved
     5     Asynchronous mapping of E4             SDH
     6     Asynchronous mapping of DS3/T3         SDH
     7     Asynchronous mapping of E3             SDH
     8     Bit synchronous mapping of E3          SDH
     9     Byte synchronous mapping of E3         SDH
    10     Asynchronous mapping of DS2/T2         SDH
    11     Bit synchronous mapping of DS2/T2      SDH
    12     Reserved
    13     Asynchronous mapping of E1             SDH
    14     Byte synchronous mapping of E1         SDH
    15     Byte synchronous mapping of 31 * DS0   SDH
    16     Asynchronous mapping of DS1/T1         SDH
    17     Bit synchronous mapping of DS1/T1      SDH
    18     Byte synchronous mapping of DS1/T1     SDH
    19     VC-11 in VC-12                         SDH
    20     Reserved
    21     Reserved
    22     DS1 SF Asynchronous                    SONET
    23     DS1 ESF Asynchronous                   SONET
    24     DS3 M23 Asynchronous                   SONET
    25     DS3 C-Bit Parity Asynchronous          SONET
    26     VT/LOVC                                SDH
    27     STS SPE/HOVC                           SDH
    28     POS - No Scrambling, 16 bit CRC        SDH
    29     POS - No Scrambling, 32 bit CRC        SDH
    30     POS - Scrambling, 16 bit CRC           SDH
    31     POS - Scrambling, 32 bit CRC           SDH
    32     ATM mapping                            SDH
    33     Ethernet                               SDH, Lambda, Fiber
    34     SONET/SDH                              Lambda, Fiber
    35     Reserved (SONET deprecated)            Lambda, Fiber
    36     Digital Wrapper                        Lambda, Fiber
    37     Lambda                                 Fiber



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    38     ANSI/ETSI PDH                          SDH
    39     Reserved                               SDH
    40     Link Access Protocol SDH               SDH
           (LAPS - X.85 and X.86)
    41     FDDI                                   SDH, Lambda, Fiber
    42     DQDB (ETSI ETS 300 216)                SDH
    43     FiberChannel-3 (Services)              FiberChannel
    44     HDLC                                   SDH
    45     Ethernet V2/DIX (only)                 SDH, Lambda, Fiber
    46     Ethernet 802.3 (only)                  SDH, Lambda, Fiber

<span class="h4"><a class="selflink" id="section-3.1.2" href="#section-3.1.2">3.1.2</a>. Bandwidth Encoding</span>

   Bandwidth encodings are carried in 32 bit number in IEEE floating
   point format (the unit is bytes per second).  For non-packet LSPs, it
   is useful to define discrete values to identify the bandwidth of the
   LSP.  Some typical values for the requested bandwidth are enumerated
   below.  (These values are guidelines.)  Additional values will be
   defined as needed.  Bandwidth encoding values are carried in a per
   protocol specific manner, see [<a href="./rfc3473" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions&quot;">RFC3473</a>] and [<a href="./rfc3472" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions&quot;">RFC3472</a>].

     Signal Type   (Bit-rate)              Value (Bytes/Sec)
                                         (IEEE Floating point)
   --------------  ---------------       ---------------------
              DS0  (0.064 Mbps)              0x45FA0000
              DS1  (1.544 Mbps)              0x483C7A00
               E1  (2.048 Mbps)              0x487A0000
              DS2  (6.312 Mbps)              0x4940A080
               E2  (8.448 Mbps)              0x4980E800
         Ethernet  (10.00 Mbps)              0x49989680
               E3  (34.368 Mbps)             0x4A831A80
              DS3  (44.736 Mbps)             0x4AAAA780
            STS-1  (51.84 Mbps)              0x4AC5C100
    Fast Ethernet  (100.00 Mbps)             0x4B3EBC20
               E4  (139.264 Mbps)            0x4B84D000
        FC-0 133M                            0x4B7DAD68
       OC-3/STM-1  (155.52 Mbps)             0x4B9450C0
        FC-0 266M                            0x4BFDAD68
        FC-0 531M                            0x4C7D3356
      OC-12/STM-4  (622.08 Mbps)             0x4C9450C0
             GigE  (1000.00 Mbps)            0x4CEE6B28
       FC-0 1062M                            0x4CFD3356
     OC-48/STM-16  (2488.32 Mbps)            0x4D9450C0
    OC-192/STM-64  (9953.28 Mbps)            0x4E9450C0
       10GigE-LAN  (10000.00 Mbps)           0x4E9502F9
   OC-768/STM-256  (39813.12 Mbps)           0x4F9450C0





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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-11" ></span>
<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>. Generalized Label</span>

   The Generalized Label extends the traditional label by allowing the
   representation of not only labels which travel in-band with
   associated data packets, but also labels which identify time-slots,
   wavelengths, or space division multiplexed positions.  For example,
   the Generalized Label may carry a label that represents (a) a single
   fiber in a bundle, (b) a single waveband within fiber, (c) a single
   wavelength within a waveband (or fiber), or (d) a set of time-slots
   within a wavelength (or fiber).  It may also carry a label that
   represents a generic MPLS label, a Frame Relay label, or an ATM label
   (VCI/VPI).

   A Generalized Label does not identify the "class" to which the label
   belongs.  This is implicit in the multiplexing capabilities of the
   link on which the label is used.

   A Generalized Label only carries a single level of label, i.e., it is
   non-hierarchical.  When multiple levels of label (LSPs within LSPs)
   are required, each LSP must be established separately, see [MPLS-
   HIERARCHY].

   Each Generalized Label object/TLV carries a variable length label
   parameter.

<span class="h4"><a class="selflink" id="section-3.2.1" href="#section-3.2.1">3.2.1</a>. Required Information</span>

   The information carried in a Generalized Label is:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Label                             |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Label: Variable Length

         Carries label information.  The interpretation of this field
         depends on the type of the link over which the label is used.

<span class="h5"><a class="selflink" id="section-3.2.1.1" href="#section-3.2.1.1">3.2.1.1</a>. Port and Wavelength Labels</span>

   Some configurations of fiber switching (FSC) and lambda switching
   (LSC) use multiple data channels/links controlled by a single control
   channel.  In such cases the label indicates the data channel/link to
   be used for the LSP.  Note that this case is not the same as when
   [<a href="#ref-MPLS-BUNDLE" title="&quot;Link Bundling in MPLS Traffic Engineering&quot;">MPLS-BUNDLE</a>] is being used.



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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-12" ></span>
<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


   The information carried in a Port and Wavelength label is:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Label                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Label: 32 bits

      Indicates port/fiber or lambda to be used, from the perspective of
      the sender of the object/TLV.  Values used in this field only have
      significance between two neighbors, and the receiver may need to
      convert the received value into a value that has local
      significance.  Values may be configured or dynamically determined
      using a protocol such as [<a href="#ref-LMP" title="&quot;Link Management Protocol&quot;">LMP</a>].

<span class="h5"><a class="selflink" id="section-3.2.1.2" href="#section-3.2.1.2">3.2.1.2</a>. Other Labels</span>

   Generic MPLS labels and Frame Relay labels are encoded right
   justified aligned in 32 bits (4 octets).  ATM labels are encoded with
   the VPI right justified in bits 0-15 and the VCI right justified in
   bits 16-31.

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

   A special case of lambda switching is waveband switching.  A waveband
   represents a set of contiguous wavelengths which can be switched
   together to a new waveband.  For optimization reasons it may be
   desirable for an optical cross connect to optically switch multiple
   wavelengths as a unit.  This may reduce the distortion on the
   individual wavelengths and may allow tighter separation of the
   individual wavelengths.  The Waveband Label is defined to support
   this special case.

   Waveband switching naturally introduces another level of label
   hierarchy and as such the waveband is treated the same way all other
   upper layer labels are treated.

   As far as the MPLS protocols are concerned there is little difference
   between a waveband label and a wavelength label except that
   semantically the waveband can be subdivided into wavelengths whereas
   the wavelength can only be subdivided into time or statistically
   multiplexed labels.







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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-13" ></span>
<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


<span class="h4"><a class="selflink" id="section-3.3.1" href="#section-3.3.1">3.3.1</a>. Required information</span>

   Waveband switching uses the same format as the generalized label, see
   <a href="#section-3.2.1">section 3.2.1</a>.

   In the context of waveband switching, the generalized label has the
   following format:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Waveband Id                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Start Label                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           End Label                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Waveband Id: 32 bits

         A waveband identifier.  The value is selected by the sender and
         reused in all subsequent related messages.

      Start Label: 32 bits

         Indicates the channel identifier of the lowest value wavelength
         making up the waveband, from the object/TLV sender's
         perspective.

      End Label: 32 bits

         Indicates the channel identifier of the highest value
         wavelength making up the waveband, from the object/TLV sender's
         perspective.

   Channel identifiers are established either by configuration or by
   means of a protocol such as LMP [<a href="#ref-LMP" title="&quot;Link Management Protocol&quot;">LMP</a>].  They are normally used in the
   label parameter of the Generalized Label one PSC and LSC.

<span class="h3"><a class="selflink" id="section-3.4" href="#section-3.4">3.4</a>. Suggested Label</span>

   The Suggested Label is used to provide a downstream node with the
   upstream node's label preference.  This permits the upstream node to
   start configuring its hardware with the proposed label before the
   label is communicated by the downstream node.  Such early
   configuration is valuable to systems that take non-trivial time to
   establish a label in hardware.  Such early configuration can reduce




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<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


   setup latency, and may be important for restoration purposes where
   alternate LSPs may need to be rapidly established as a result of
   network failures.

   The use of Suggested Label is only an optimization.  If a downstream
   node passes a different label upstream, an upstream LSR reconfigures
   itself so that it uses the label specified by the downstream node,
   thereby maintaining the downstream control of a label.  Note, the
   transmission of a suggested label does not imply that the suggested
   label is available for use.  In particular, an ingress node should
   not transmit data traffic on a suggested label until the downstream
   node passes a label upstream.

   The information carried in a suggested label is identical to a
   generalized label.  Note, values used in the label field of a
   suggested label are from the object/TLV sender's perspective.

<span class="h3"><a class="selflink" id="section-3.5" href="#section-3.5">3.5</a>. Label Set</span>

   The Label Set is used to limit the label choices of a downstream node
   to a set of acceptable labels.  This limitation applies on a per hop
   basis.

   We describe four cases where a Label Set is useful in the optical
   domain.  The first case is where the end equipment is only capable of
   transmitting on a small specific set of wavelengths/bands.  The
   second case is where there is a sequence of interfaces which cannot
   support wavelength conversion (CI-incapable) and require the same
   wavelength be used end-to-end over a sequence of hops, or even an
   entire path.  The third case is where it is desirable to limit the
   amount of wavelength conversion being performed to reduce the
   distortion on the optical signals.  The last case is where two ends
   of a link support different sets of wavelengths.

   Label Set is used to restrict label ranges that may be used for a
   particular LSP between two peers.  The receiver of a Label Set must
   restrict its choice of labels to one which is in the Label Set.  Much
   like a label, a Label Set may be present across multiple hops.  In
   this case each node generates its own outgoing Label Set, possibly
   based on the incoming Label Set and the node's hardware capabilities.
   This case is expected to be the norm for nodes with conversion
   incapable (CI-incapable) interfaces.

   The use of Label Set is optional, if not present, all labels from the
   valid label range may be used.  Conceptually the absence of a Label
   Set implies a Label Set whose value is {U}, the set of all valid
   labels.




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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-15" ></span>
<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


<span class="h4"><a class="selflink" id="section-3.5.1" href="#section-3.5.1">3.5.1</a>. Required Information</span>

   A label set is composed of one or more Label_Set objects/TLVs.  Each
   object/TLV contains one or more elements of the Label Set.  Each
   element is referred to as a subchannel identifier and has the same
   format as a generalized label.

   The information carried in a Label_Set is:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Action     |      Reserved     |        Label Type         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Subchannel 1                         |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                               :                               :
   :                               :                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Subchannel N                         |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Action: 8 bits

      0 - Inclusive List

         Indicates that the object/TLV contains one or more subchannel
         elements that are included in the Label Set.

      1 - Exclusive List

         Indicates that the object/TLV contains one or more subchannel
         elements that are excluded from the Label Set.

      2 - Inclusive Range

         Indicates that the object/TLV contains a range of labels.  The
         object/TLV contains two subchannel elements.  The first element
         indicates the start of the range.  The second element indicates
         the end of the range.  A value of zero indicates that there is
         no bound on the corresponding portion of the range.








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<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


      3 - Exclusive Range

         Indicates that the object/TLV contains a range of labels that
         are excluded from the Label Set.  The object/TLV contains two
         subchannel elements.  The first element indicates the start of
         the range.  The second element indicates the end of the range.
         A value of zero indicates that there is no bound on the
         corresponding portion of the range.

   Reserved: 10 bits

      This field is reserved. It MUST be set to zero on transmission and
      MUST be ignored on receipt.

   Label Type: 14 bits

      Indicates the type and format of the labels carried in the
      object/TLV.  Values are signaling protocol specific.

   Subchannel:

      The subchannel represents the label (wavelength, fiber ... ) which
      is eligible for allocation.  This field has the same format as
      described for labels under <a href="#section-3.2">section 3.2</a>.

      Note that subchannel to local channel identifiers (e.g.,
      wavelength) mappings are a local matter.

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

   This section defines direct support of bidirectional LSPs.  Support
   is defined for LSPs that have the same traffic engineering
   requirements including fate sharing, protection and restoration,
   LSRs, and resource requirements (e.g., latency and jitter) in each
   direction.  In the remainder of this section, the term "initiator" is
   used to refer to a node that starts the establishment of an LSP and
   the term "terminator" is used to refer to the node that is the target
   of the LSP.  Note that for bidirectional LSPs, there is only one
   "initiator" and one "terminator".

   Normally to establish a bidirectional LSP when using [<a href="./rfc3209" title="&quot;RSVP-TE: Extensions to RSVP for LSP Tunnels&quot;">RFC3209</a>] or
   [<a href="./rfc3212" title="&quot;Constraint-Based LSP Setup using LDP&quot;">RFC3212</a>] two unidirectional paths must be independently established.
   This approach has the following disadvantages:

   *  The latency to establish the bidirectional LSP is equal to one
      round trip signaling time plus one initiator-terminator signaling
      transit delay.  This not only extends the setup latency for
      successful LSP establishment, but it extends the worst-case



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<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


      latency for discovering an unsuccessful LSP to as much as two
      times the initiator-terminator transit delay.  These delays are
      particularly significant for LSPs that are established for
      restoration purposes.

   *  The control overhead is twice that of a unidirectional LSP.  This
      is because separate control messages (e.g., Path and Resv) must be
      generated for both segments of the bidirectional LSP.

   *  Because the resources are established in separate segments, route
      selection is complicated.  There is also additional potential race
      for conditions in assignment of resources, which decreases the
      overall probability of successfully establishing the bidirectional
      connection.

   *  It is more difficult to provide a clean interface for SONET/SDH
      equipment that may rely on bidirectional hop-by-hop paths for
      protection switching.

   *  Bidirectional optical LSPs (or lightpaths) are seen as a
      requirement for many optical networking service providers.

   With bidirectional LSPs both the downstream and upstream data paths,
   i.e., from initiator to terminator and terminator to initiator, they
   are established using a single set of signaling messages.  This
   reduces the setup latency to essentially one initiator-terminator
   round trip time plus processing time, and limits the control overhead
   to the same number of messages as a unidirectional LSP.

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

   For bidirectional LSPs, two labels must be allocated.  Bidirectional
   LSP setup is indicated by the presence of an Upstream Label
   object/TLV in the appropriate signaling message.  An Upstream Label
   has the same format as the generalized label, see <a href="#section-3.2">Section 3.2</a>.

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

   Contention for labels may occur between two bidirectional LSP setup
   requests traveling in opposite directions.  This contention occurs
   when both sides allocate the same resources (labels) at effectively
   the same time.  If there is no restriction on the labels that can be
   used for bidirectional LSPs and if there are alternate resources,
   then both nodes will pass different labels upstream and there is no
   contention.  However, if there is a restriction on the labels that
   can be used for the bidirectional LSPs (for example, if they must be
   physically coupled on a single I/O card), or if there are no more
   resources available, then the contention must be resolved by other



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<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


   means.  To resolve contention, the node with the higher node ID will
   win the contention and it MUST issue a PathErr/NOTIFICATION message
   with a "Routing problem/Label allocation failure" indication.  Upon
   receipt of such an error, the node SHOULD try to allocate a different
   Upstream label (and a different Suggested Label if used) to the
   bidirectional path.  However, if no other resources are available,
   the node must proceed with standard error handling.

   To reduce the probability of contention, one may impose a policy that
   the node with the lower ID never suggests a label in the downstream
   direction and always accepts a Suggested Label from an upstream node
   with a higher ID.  Furthermore, since the labels may be exchanged
   using LMP, an alternative local policy could further be imposed such
   that (with respect to the higher numbered node's label set) the
   higher numbered node could allocate labels from the high end of the
   label range while the lower numbered node allocates labels from the
   low end of the label range.  This mechanism would augment any close
   packing algorithms that may be used for bandwidth (or wavelength)
   optimization.  One special case that should be noted when using RSVP
   and supporting this approach is that the neighbor's node ID might not
   be known when sending an initial Path message.  When this case
   occurs, a node should suggest a label chosen at random from the
   available label space.

   An example of contention between two nodes (PXC 1 and PXC 2) is shown
   in Figure 1.  In this example PXC 1 assigns an Upstream Label for the
   channel corresponding to local BCId=2 (local BCId=7 on PXC 2) and
   sends a Suggested Label for the channel corresponding to local BCId=1
   (local BCId=6 on PXC 2).  Simultaneously, PXC 2 assigns an Upstream
   Label for the channel corresponding to its local BCId=6 (local BCId=1
   on PXC 1) and sends a Suggested Label for the channel corresponding
   to its local BCId=7 (local BCId=2 on PXC 1).  If there is no
   restriction on the labels that can be used for bidirectional LSPs and
   if there are alternate resources available, then both PXC 1 and PXC 2
   will pass different labels upstream and the contention is resolved
   naturally (see Fig. 2).  However, if there is a restriction on the
   labels that can be used for bidirectional LSPs (for example, if they
   must be physically coupled on a single I/O card), then the contention
   must be resolved using the node ID (see Fig. 3).












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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-19" ></span>
<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


        +------------+                         +------------+
        +   PXC 1    +                         +   PXC 2    +
        +            +                 SL1,UL2 +            +
        +          1 +------------------------&gt;+ 6          +
        +            + UL1, SL2                +            +
        +          2 +&lt;------------------------+ 7          +
        +            +                         +            +
        +            +                         +            +
        +          3 +------------------------&gt;+ 8          +
        +            +                         +            +
        +          4 +&lt;------------------------+ 9          +
        +------------+                         +------------+
                           Figure 1.  Label Contention

   In this example, PXC 1 assigns an Upstream Label using BCId=2 (BCId=7
   on PXC 2) and a Suggested Label using BCId=1 (BCId=6 on PXC 2).
   Simultaneously, PXC 2 assigns an Upstream Label using BCId=6 (BCId=1
   on PXC 1) and a Suggested Label using BCId=7 (BCId=2 on PXC 1).

        +------------+                         +------------+
        +   PXC 1    +                         +   PXC 2    +
        +            +                     UL2 +            +
        +          1 +------------------------&gt;+ 6          +
        +            + UL1                     +            +
        +          2 +&lt;------------------------+ 7          +
        +            +                         +            +
        +            +                      L1 +            +
        +          3 +------------------------&gt;+ 8          +
        +            + L2                      +            +
        +          4 +&lt;------------------------+ 9          +
        +------------+                         +------------+

    Figure 2. Label Contention Resolution without resource restrictions


















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<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


   In this example, there is no restriction on the labels that can be
   used by the bidirectional connection and there is no contention.

        +------------+                         +------------+
        +   PXC 1    +                         +   PXC 2    +
        +            +                     UL2 +            +
        +          1 +------------------------&gt;+ 6          +
        +            + L2                      +            +
        +          2 +&lt;------------------------+ 7          +
        +            +                         +            +
        +            +                      L1 +            +
        +          3 +------------------------&gt;+ 8          +
        +            +  UL1                    +            +
        +          4 +&lt;------------------------+ 9          +
        +------------+                         +------------+

     Figure 3. Label Contention Resolution with resource restrictions

   In this example, labels 1,2 and 3,4 on PXC 1 (labels 6,7 and 8,9 on
   PXC 2, respectively) must be used by the same bidirectional
   connection.  Since PXC 2 has a higher node ID, it wins the contention
   and PXC 1 must use a different set of labels.

<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Notification on Label Error</span>

   There are cases in traditional MPLS and in GMPLS that result in an
   error message containing an "Unacceptable label value" indication,
   see [<a href="./rfc3209" title="&quot;RSVP-TE: Extensions to RSVP for LSP Tunnels&quot;">RFC3209</a>], [<a href="./rfc3472" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions&quot;">RFC3472</a>] and [<a href="./rfc3473" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions&quot;">RFC3473</a>].  When these cases occur, it
   can be useful for the node generating the error message to indicate
   which labels would be acceptable.  To cover this case, GMPLS
   introduces the ability to convey such information via the "Acceptable
   Label Set".  An Acceptable Label Set is carried in appropriate
   protocol specific error messages, see [<a href="./rfc3472" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions&quot;">RFC3472</a>] and [<a href="./rfc3473" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions&quot;">RFC3473</a>].

   The format of an Acceptable Label Set is identical to a Label Set,
   see <a href="#section-3.5.1">section 3.5.1</a>.

<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Explicit Label Control</span>

   In traditional MPLS, the interfaces used by an LSP may be controlled
   via an explicit route, i.e., ERO or ER-Hop.  This enables the
   inclusion of a particular node/interface, and the termination of an
   LSP on a particular outgoing interface of the egress LSR.  Where the
   interface may be numbered or unnumbered, see [MPLS-UNNUM].

   There are cases where the existing explicit route semantics do not
   provide enough information to control the LSP to the degree desired.
   This occurs in the case when the LSP initiator wishes to select a



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<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


   label used on a link.  Specifically, the problem is that ERO and ER-
   Hop do not support explicit label sub-objects.  An example case where
   such a mechanism is desirable is where there are two LSPs to be
   "spliced" together, i.e., where the tail of the first LSP would be
   "spliced" into the head of the second LSP.  This last case is more
   likely to be used in the non-PSC classes of links.

   To cover this case, the Label ERO subobject / ER Hop is introduced.

<span class="h3"><a class="selflink" id="section-6.1" href="#section-6.1">6.1</a>. Required Information</span>

   The Label Explicit and Record Routes contains:

      L: 1 bit

         This bit must be set to 0.

      U: 1 bit

         This bit indicates the direction of the label.  It is 0 for the
         downstream label.  It is set to 1 for the upstream label and is
         only used on bidirectional LSPs.

      Label: Variable

         This field identifies the label to be used.  The format of this
         field is identical to the one used by the Label field in
         Generalized Label, see <a href="#section-3.2.1">Section 3.2.1</a>.

   Placement and ordering of these parameters are signaling protocol
   specific.

<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. Protection Information</span>

   Protection Information is carried in a new object/TLV.  It is used to
   indicate link related protection attributes of a requested LSP.  The
   use of Protection Information for a particular LSP is optional.
   Protection Information currently indicates the link protection type
   desired for the LSP.  If a particular protection type, i.e., 1+1, or
   1:N, is requested, then a connection request is processed only if the
   desired protection type can be honored.  Note that the protection
   capabilities of a link may be advertised in routing, see [<a href="#ref-GMPLS-RTG" title="&quot;Routing Extensions in Support of Generalized MPLS&quot;">GMPLS-RTG</a>].
   Path computation algorithms may take this information into account
   when computing paths for setting up LSPs.

   Protection Information also indicates if the LSP is a primary or
   secondary LSP.  A secondary LSP is a backup to a primary LSP.  The
   resources of a secondary LSP are not used until the primary LSP



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   fails.  The resources allocated for a secondary LSP MAY be used by
   other LSPs until the primary LSP fails over to the secondary LSP.  At
   that point, any LSP that is using the resources for the secondary LSP
   MUST be preempted.

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

   The following information is carried in Protection Information:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |S|                  Reserved                       | Link Flags|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Secondary (S): 1 bit

         When set, indicates that the requested LSP is a secondary LSP.

      Reserved: 25 bits

         This field is reserved. It MUST be set to zero on transmission
         and MUST be ignored on receipt.  These bits SHOULD be pass
         through unmodified by transit nodes.

      Link Flags: 6 bits

         Indicates desired link protection type.  As previously
         mentioned, protection capabilities of a link may be advertised
         in routing.  A value of 0 implies that any, including no, link
         protection may be used.  More than one bit may be set to
         indicate when multiple protection types are acceptable.  When
         multiple bits are set and multiple protection types are
         available, the choice of protection type is a local (policy)
         decision.

         The following flags are defined:

         0x20  Enhanced

      Indicates that a protection scheme that is more reliable than
      Dedicated 1+1 should be used, e.g., 4 fiber BLSR/MS-SPRING.









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         0x10  Dedicated 1+1

            Indicates that a dedicated link layer protection scheme,
            i.e., 1+1 protection, should be used to support the LSP.

         0x08  Dedicated 1:1

            Indicates that a dedicated link layer protection scheme,
            i.e., 1:1 protection, should be used to support the LSP.

         0x04  Shared

            Indicates that a shared link layer protection scheme, such
            as 1:N protection, should be used to support the LSP.

         0x02  Unprotected

            Indicates that the LSP should not use any link layer
            protection.

         0x01  Extra Traffic

            Indicates that the LSP should use links that are protecting
            other (primary) traffic.  Such LSPs may be preempted when
            the links carrying the (primary) traffic being protected
            fail.

<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. Administrative Status Information</span>

   Administrative Status Information is carried in a new object/TLV.
   Administrative Status Information is currently used in two ways.  In
   the first, the information indicates administrative state with
   respect to a particular LSP.  In this usage, Administrative Status
   Information indicates the state of the LSP.  State indications
   include "up" or "down", if it is in a "testing" mode, and if deletion
   is in progress.  The actions taken by a node based on a state local
   decision.  An example action that may be taken is to inhibit alarm
   reporting when an LSP is in "down" or "testing" states, or to report
   alarms associated with the connection at a priority equal to or less
   than "Non service affecting".

   In the second usage of Administrative Status Information, the
   information indicates a request to set an LSP's administrative state.
   This information is always relayed to the ingress node which acts on
   the request.






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   The different usages are distinguished in a protocol specific
   fashion.  See [<a href="./rfc3473" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions&quot;">RFC3473</a>] and [<a href="./rfc3472" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions&quot;">RFC3472</a>] for details.  The use of
   Administrative Status Information for a particular LSP is optional.

<span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>. Required Information</span>

   The following information is carried in Administrative Status
   Information:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|                        Reserved                       |T|A|D|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Reflect (R): 1 bit

         When set, indicates that the edge node SHOULD reflect the
         object/TLV back in the appropriate message.  This bit MUST NOT
         be set in state change request, i.e., Notify, messages.

      Reserved: 28 bits

         This field is reserved.  It MUST be set to zero on transmission
         and MUST be ignored on receipt.  These bits SHOULD be pass
         through unmodified by transit nodes.

      Testing (T): 1 bit

         When set, indicates that the local actions related to the
         "testing" mode should be taken.

      Administratively down (A): 1 bit

         When set, indicates that the local actions related to the
         "administratively down" state should be taken.

      Deletion in progress (D): 1 bit

         When set, indicates that that the local actions related to LSP
         teardown should be taken.  Edge nodes may use this flag to
         control connection teardown.









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<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>. Control Channel Separation</span>

   The concept of a control channel being different than a data channel
   being signaled was introduced to MPLS in connection with link
   bundling, see [<a href="#ref-MPLS-BUNDLE" title="&quot;Link Bundling in MPLS Traffic Engineering&quot;">MPLS-BUNDLE</a>].  In GMPLS, the separation of control and
   data channel may be due to any number of factors.  (Including
   bundling and other cases such as data channels that cannot carry in-
   band control information.)  This section will cover the two critical
   related issues: the identification of data channels in signaling and
   handling of control channel failures that don't impact data channels.

<span class="h3"><a class="selflink" id="section-9.1" href="#section-9.1">9.1</a>. Interface Identification</span>

   In traditional MPLS there is an implicit one-to-one association of a
   control channel to a data channel.  When such an association is
   present, no additional or special information is required to
   associate a particular LSP setup transaction with a particular data
   channel.  (It is implicit in the control channel over which the
   signaling messages are sent.)

   In cases where there is not an explicit one-to-one association of
   control channels to data channels it is necessary to convey
   additional information in signaling to identify the particular data
   channel being controlled.  GMPLS supports explicit data channel
   identification by providing interface identification information.
   GMPLS allows the use of a number of interface identification schemes
   including IPv4 or IPv6 addresses, interface indexes (see [MPLS-
   UNNUM]) and component interfaces (established via configuration or a
   protocol such as [<a href="#ref-LMP" title="&quot;Link Management Protocol&quot;">LMP</a>]).  In all cases the choice of the data
   interface is indicated by the upstream node using addresses and
   identifiers used by the upstream node.

<span class="h4"><a class="selflink" id="section-9.1.1" href="#section-9.1.1">9.1.1</a>. Required Information</span>

   The following information is carried in Interface_ID:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                              TLVs                             ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+








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   Where each TLV has the following format:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                             Value                             ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Length: 16 bits

         Indicates the total length of the TLV, i.e., 4 + the length of
         the value field in octets.  A value field whose length is not a
         multiple of four MUST be zero-padded so that the TLV is four-
         octet aligned.

      Type: 16 bits

         Indicates type of interface being identified.  Defined values
         are:

   Type Length Format     Description
   --------------------------------------------------------------------
    1      8   IPv4 Addr. IPv4
    2     20   IPv6 Addr. IPv6
    3     12   See below  IF_INDEX                (Interface Index)
    4     12   See below  COMPONENT_IF_DOWNSTREAM (Component interface)
    5     12   See below  COMPONENT_IF_UPSTREAM   (Component interface)

   For types 3, 4 and 5 the Value field has the format:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            IP Address                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Interface ID                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      IP Address: 32 bits

         The IP address field may carry either an IP address of a link
         or an IP address associated with the router, where associated
         address is the value carried in a router address TLV of
         routing.



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      Interface ID: 32 bits

         For type 3 usage, the Interface ID carries an interface
         identifier.

         For types 4 and 5, the Interface ID indicates a bundled
         component link.  The special value 0xFFFFFFFF can be used to
         indicate the same label is to be valid across all component
         links.

<span class="h3"><a class="selflink" id="section-9.2" href="#section-9.2">9.2</a>. Fault Handling</span>

   There are two new faults that must be handled when the control
   channel is independent of the data channel.  In the first, there is a
   link or other type of failure that limits the ability of neighboring
   nodes to pass control messages.  In this situation, neighboring nodes
   are unable to exchange control messages for a period of time.  Once
   communication is restored the underlying signaling protocol must
   indicate that the nodes have maintained their state through the
   failure.  The signaling protocol must also ensure that any state
   changes that were instantiated during the failure are synchronized
   between the nodes.

   In the second, a node's control plane fails and then restarts and
   losses most of its state information.  In this case, both upstream
   and downstream nodes must synchronize their state information with
   the restarted node.  In order for any resynchronization to occur the
   node undergoing the restart will need to preserve some information,
   such as its mappings of incoming to outgoing labels.

   Both cases are addressed in protocol specific fashions, see [<a href="./rfc3473" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions&quot;">RFC3473</a>]
   and [<a href="./rfc3472" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions&quot;">RFC3472</a>].

   Note that these cases only apply when there are mechanisms to detect
   data channel failures independent of control channel failures.

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

   This document is the work of numerous authors and consists of a
   composition of a number of previous documents in this area.

   Valuable comments and input were received from a number of people,
   including Igor Bryskin, Adrian Farrel, Ben Mack-Crane, Dimitri
   Papadimitriou, Fong Liaw and Juergen Heiles.  Some sections of this
   document are based on text proposed by Fong Liaw.






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<span class="h2"><a class="selflink" id="section-11" href="#section-11">11</a>. Security Considerations</span>

   This document introduce no new security considerations to either
   [<a href="./rfc3212" title="&quot;Constraint-Based LSP Setup using LDP&quot;">RFC3212</a>] or [<a href="./rfc3209" title="&quot;RSVP-TE: Extensions to RSVP for LSP Tunnels&quot;">RFC3209</a>].  The security considerations mentioned in
   [<a href="./rfc3212" title="&quot;Constraint-Based LSP Setup using LDP&quot;">RFC3212</a>] or [<a href="./rfc3209" title="&quot;RSVP-TE: Extensions to RSVP for LSP Tunnels&quot;">RFC3209</a>] apply to the respective protocol specific
   forms of GMPLS, see [<a href="./rfc3473" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions&quot;">RFC3473</a>] and [<a href="./rfc3472" title="&quot;Generalized Multi-Protocol Label Switching (GMPLS) Signaling - Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions&quot;">RFC3472</a>].

<span class="h2"><a class="selflink" id="section-12" href="#section-12">12</a>. IANA Considerations</span>

   The IANA will administer assignment of new values for namespaces
   defined in this document.  This section uses the terminology of <a href="https://www.rfc-editor.org/bcp/bcp26">BCP</a>
   <a href="https://www.rfc-editor.org/bcp/bcp26">26</a> "Guidelines for Writing an IANA Considerations Section in RFCs"
   [BCP26].

   This document defines the following namespaces:

      o LSP Encoding Type: 8 bits
      o Switching Type: 8 bits
      o Generalized PID (G-PID): 16 bits
      o Action: 8 bits
      o Interface_ID Type: 16 bits

   All future assignments should be allocated through IETF Consensus
   action or documented in a Specification.

   LSP Encoding Type - valid value range is 1-255.  This document
   defines values 1-11.

   Switching Type - valid value range is 1-255.  This document defines
   values 1-4, 100, 150 and 200.

   Generalized PID (G-PID) - valid value range is 0-1500.  This document
   defines values 0-46.

   Action - valid value range is 0-255.  This document defines values
   0-3.

   Interface_ID Type - valid value range is 1-65535.  This document
   defines values 1-5.












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<span class="h2"><a class="selflink" id="section-13" href="#section-13">13</a>. Intellectual Property Considerations</span>

   This section is taken from <a href="./rfc2026#section-10.4">Section&nbsp;10.4 of [RFC2026]</a>.

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in <a href="https://www.rfc-editor.org/bcp/bcp11">BCP-11</a>.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

<span class="h2"><a class="selflink" id="section-14" href="#section-14">14</a>. References</span>

<span class="h3"><a class="selflink" id="section-14.1" href="#section-14.1">14.1</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-RFC3036">RFC3036</a>]        Andersson, L., Doolan, P., Feldman, N., Fredette, A.
                    and B. Thomas, "LDP Specification", <a href="./rfc3036">RFC 3036</a>,
                    January 2001.

   [<a id="ref-RFC3209">RFC3209</a>]        Awduche, D., Berger, L., Gan, D., Li, T.,
                    Srinivasan, V.  and G. Swallow, "RSVP-TE: Extensions
                    to RSVP for LSP Tunnels", <a href="./rfc3209">RFC 3209</a>, December 2001.

   [<a id="ref-RFC3212">RFC3212</a>]        Jamoussi, B., Andersson, L., Callon, R., Dantu, R.,
                    Wu, L., Doolan, P., Worster, T., Feldman, N.,
                    Fredette, A., Girish, M., Gray, E., Heinanen, J.,
                    Kilty, T. and A. Malis, "Constraint-Based LSP Setup
                    using LDP", <a href="./rfc3212">RFC 3212</a>, January 2002.







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   [<a id="ref-RFC3472">RFC3472</a>]        Ashwood-Smith, P. and L. Berger, Editors,
                    "Generalized Multi-Protocol Label Switching (GMPLS)
                    Signaling - Constraint-based Routed Label
                    Distribution Protocol (CR-LDP) Extensions", <a href="./rfc3472">RFC</a>
                    <a href="./rfc3472">3472</a>, January 2003.

   [<a id="ref-RFC3473">RFC3473</a>]        Berger, L., Editor "Generalized Multi-Protocol Label
                    Switching (GMPLS) Signaling - Resource ReserVation
                    Protocol-Traffic Engineering (RSVP-TE) Extensions",
                    <a href="./rfc3473">RFC 3473</a>, January 2003.

<span class="h3"><a class="selflink" id="section-14.2" href="#section-14.2">14.2</a>. Informative References</span>

   [<a id="ref-GMPLS-RTG">GMPLS-RTG</a>]      Kompella, K., et al., "Routing Extensions in Support
                    of Generalized MPLS", Work in Progress.

   [<a id="ref-GMPLS-SONET">GMPLS-SONET</a>]    Ashwood-Smith, P., et al., "GMPLS - SONET / SDH
                    Specifics", Work in Progress.

   [<a id="ref-LMP">LMP</a>]            Lang, et al., <a style="text-decoration: none" href='https://www.google.com/search?sitesearch=datatracker.ietf.org%2Fdoc%2Fhtml%2F&amp;q=inurl:draft-+%22Link+Management+Protocol%22'>"Link Management Protocol"</a>, Work in
                    Progress.

   [<a id="ref-MPLS-BUNDLE">MPLS-BUNDLE</a>]    Kompella, K., Rekhter, Y. and L. Berger, "Link
                    Bundling in MPLS Traffic Engineering", Work in
                    Progress.

   [<a id="ref-MPLS-HIERARCHY">MPLS-HIERARCHY</a>] Kompella, K. and Y. Rekhter, "LSP Hierarchy with
                    MPLS TE", Work in Progress.

   [<a id="ref-RFC2026">RFC2026</a>]        Bradner, S., "The Internet Standards Process --
                    Revision 3," <a href="https://www.rfc-editor.org/bcp/bcp9">BCP 9</a>, <a href="./rfc2026">RFC 2026</a>, October 1996.

   [<a id="ref-RFC2434">RFC2434</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</a>
                    <a href="https://www.rfc-editor.org/bcp/bcp26">26</a>, <a href="./rfc2434">RFC 2434</a>, October 1998.

   [<a id="ref-RFC3031">RFC3031</a>]        Rosen, E., Viswanathan, A. and R. Callon,
                    "Multiprotocol label switching Architecture", <a href="./rfc3031">RFC</a>
                    <a href="./rfc3031">3031</a>, January 2001.












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<span class="h2"><a class="selflink" id="section-15" href="#section-15">15</a>. Contributors</span>

   Peter Ashwood-Smith
   Nortel Networks Corp.
   P.O. Box 3511 Station C,
   Ottawa, ON K1Y 4H7
   Canada

   Phone:  +1 613 763 4534
   EMail:  petera@nortelnetworks.com


   Ayan Banerjee
   Calient Networks
   5853 Rue Ferrari
   San Jose, CA 95138

   Phone:  +1 408 972-3645
   EMail:  abanerjee@calient.net


   Lou Berger
   Movaz Networks, Inc.
   7926 Jones Branch Drive
   Suite 615
   McLean VA, 22102

   Phone:  +1 703 847-1801
   EMail:  lberger@movaz.com


   Greg Bernstein

   EMail:  gregb@grotto-networking.com


   John Drake
   Calient Networks
   5853 Rue Ferrari
   San Jose, CA 95138

   Phone:  +1 408 972 3720
   EMail:  jdrake@calient.net








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   Yanhe Fan
   Axiowave Networks, Inc.
   200 Nickerson Road
   Marlborough, MA 01752

   Phone: + 1 774 348 4627
   EMail: yfan@axiowave.com


   Kireeti Kompella
   Juniper Networks, Inc.
   1194 N. Mathilda Ave.
   Sunnyvale, CA 94089

   EMail:  kireeti@juniper.net


   Jonathan P. Lang
   EMail:  jplang@ieee.org


   Eric Mannie
   Independent Consultant
   2 Avenue de la Folle Chanson
   1050 Brussels
   Belgium
   EMail:  eric_mannie@hotmail.com


   Bala Rajagopalan
   Tellium, Inc.
   2 Crescent Place
   P.O. Box 901
   Oceanport, NJ 07757-0901

   Phone:  +1 732 923 4237
   Fax:    +1 732 923 9804
   EMail:  braja@tellium.com


   Yakov Rekhter
   Juniper Networks, Inc.

   EMail:  yakov@juniper.net







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   Debanjan Saha
   EMail:  debanjan@acm.org


   Vishal Sharma
   Metanoia, Inc.
   1600 Villa Street, Unit 352
   Mountain View, CA 94041-1174
   Phone:  +1 650-386-6723
   EMail:  v.sharma@ieee.org


   George Swallow
   Cisco Systems, Inc.
   250 Apollo Drive
   Chelmsford, MA 01824

   Phone:  +1 978 244 8143
   EMail:  swallow@cisco.com


   Z. Bo Tang
   EMail:  botang01@yahoo.com

<span class="h2"><a class="selflink" id="section-16" href="#section-16">16</a>. Editor's Address</span>

   Lou Berger
   Movaz Networks, Inc.
   7926 Jones Branch Drive
   Suite 615
   McLean VA, 22102

   Phone:  +1 703 847-1801
   EMail:  lberger@movaz.com

















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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-34" ></span>
<span class="grey"><a href="./rfc3471">RFC 3471</a>        GMPLS Signaling Functional Description</span>


<span class="h2"><a class="selflink" id="section-17" href="#section-17">17</a>.  Full Copyright Statement</span>

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

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