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<pre>Network Working Group I. Bryskin
Request for Comments: 4397 Independent Consultant
Category: Informational A. Farrel
Old Dog Consulting
February 2006
<span class="h1">A Lexicography for the Interpretation of Generalized Multiprotocol</span>
<span class="h1">Label Switching (GMPLS) Terminology within the Context of the</span>
<span class="h1">ITU-T's Automatically Switched Optical Network (ASON) Architecture</span>
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
Generalized Multiprotocol Label Switching (GMPLS) has been developed
by the IETF to facilitate the establishment of Label Switched Paths
(LSPs) in a variety of data plane technologies and across several
architectural models. The ITU-T has specified an architecture for
the control of Automatically Switched Optical Networks (ASON).
This document provides a lexicography for the interpretation of GMPLS
terminology within the context of the ASON architecture.
It is important to note that GMPLS is applicable in a wider set of
contexts than just ASON. The definitions presented in this document
do not provide exclusive or complete interpretations of GMPLS
concepts. This document simply allows the GMPLS terms to be applied
within the ASON context.
<span class="grey">Bryskin & Farrel Informational [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
Table of Contents
<a href="#section-1">1</a>. Introduction ....................................................<a href="#page-3">3</a>
<a href="#section-2">2</a>. Terminology .....................................................<a href="#page-3">3</a>
<a href="#section-2.1">2.1</a>. GMPLS Terminology Sources ..................................<a href="#page-3">3</a>
<a href="#section-2.2">2.2</a>. ASON Terminology Sources ...................................<a href="#page-4">4</a>
<a href="#section-2.3">2.3</a>. Common Terminology Sources .................................<a href="#page-4">4</a>
<a href="#section-3">3</a>. Lexicography ....................................................<a href="#page-4">4</a>
<a href="#section-3.1">3.1</a>. Network Presences ..........................................<a href="#page-4">4</a>
<a href="#section-3.2">3.2</a>. Resources ..................................................<a href="#page-5">5</a>
<a href="#section-3.3">3.3</a>. Layers .....................................................<a href="#page-6">6</a>
<a href="#section-3.4">3.4</a>. Labels .....................................................<a href="#page-7">7</a>
<a href="#section-3.5">3.5</a>. Data Links .................................................<a href="#page-7">7</a>
<a href="#section-3.6">3.6</a>. Link Interfaces ............................................<a href="#page-8">8</a>
<a href="#section-3.7">3.7</a>. Connections ................................................<a href="#page-9">9</a>
<a href="#section-3.8">3.8</a>. Switching, Termination, and Adaptation Capabilities .......<a href="#page-10">10</a>
<a href="#section-3.9">3.9</a>. TE Links and FAs ..........................................<a href="#page-11">11</a>
<a href="#section-3.10">3.10</a>. TE Domains ...............................................<a href="#page-13">13</a>
<a href="#section-3.11">3.11</a>. Component Links and Bundles ..............................<a href="#page-13">13</a>
<a href="#section-3.12">3.12</a>. Regions ..................................................<a href="#page-14">14</a>
<a href="#section-4">4</a>. Guidance on the Application of this Lexicography ...............<a href="#page-14">14</a>
<a href="#section-5">5</a>. Management Considerations ......................................<a href="#page-15">15</a>
<a href="#section-6">6</a>. Security Considerations ........................................<a href="#page-15">15</a>
<a href="#section-7">7</a>. Acknowledgements ...............................................<a href="#page-15">15</a>
<a href="#section-8">8</a>. Normative References ...........................................<a href="#page-16">16</a>
<a href="#section-9">9</a>. Informative References .........................................<a href="#page-16">16</a>
<span class="grey">Bryskin & Farrel Informational [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
Generalized Multiprotocol Label Switching (GMPLS) has been developed
by the IETF to facilitate the establishment of Label Switched Paths
(LSPs) in a variety of data plane technologies such as Packet
Switching Capable (PSC), Layer Two Switching Capable (L2SC), Time
Division Multiplexing (TDM), Lambda Switching Capable (LSC), and
Fiber Switching Capable (FSC).
The ITU-T has specified an architecture for the control of
Automatically Switched Optical Networks (ASON). This architecture
forms the basis of many Recommendations within the ITU-T.
Because the GMPLS and ASON architectures were developed by different
people in different standards bodies, and because the architectures
have very different historic backgrounds (the Internet, and transport
networks respectively), the terminology used is different.
This document provides a lexicography for the interpretation of GMPLS
terminology within the context of the ASON architecture. This allows
GMPLS documents to be generally understood by those familiar with
ASON Recommendations. The definitions presented in this document do
not provide exclusive or complete interpretations of the GMPLS
concepts.
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Terminology</span>
Throughout this document, angle brackets ("<" and ">") are used to
indicate the context in which a term applies. For example, "<Data
Plane>" as part of a description of a term means that the term
applies within the data plane.
<span class="h3"><a class="selflink" id="section-2.1" href="#section-2.1">2.1</a>. GMPLS Terminology Sources</span>
GMPLS terminology is principally defined in [<a href="./rfc3945" title=""Generalized Multi-Protocol Label Switching (GMPLS) Architecture"">RFC3945</a>]. Other
documents provide further key definitions including [<a href="./rfc4201" title=""Link Bundling in MPLS Traffic Engineering (TE)"">RFC4201</a>],
[<a href="./rfc4202" title=""Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)"">RFC4202</a>], [<a href="./rfc4204" title=""Link Management Protocol (LMP)"">RFC4204</a>], and [<a href="./rfc4206" title=""Label Switched Paths (LSP) Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) Traffic Engineering (TE)"">RFC4206</a>].
The reader is recommended to become familiar with these other
documents before attempting to use this document to provide a more
general mapping between GMPLS and ASON.
For details of GMPLS signaling, please refer to [<a href="./rfc3471" title=""Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description"">RFC3471</a>] and
[<a href="./rfc3473" title=""Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description"">RFC3473</a>]. For details of GMPLS routing, please refer to [<a href="./rfc4203" title=""OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)"">RFC4203</a>]
and [<a href="./rfc4205" title=""Intermediate System to Intermediate System (IS-IS) Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)"">RFC4205</a>].
<span class="grey">Bryskin & Farrel Informational [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
<span class="h3"><a class="selflink" id="section-2.2" href="#section-2.2">2.2</a>. ASON Terminology Sources</span>
The ASON architecture is specified in ITU-T Recommendation G.8080
[<a href="#ref-G-8080">G-8080</a>]. This is developed from generic functional architectures
and requirements specified in [<a href="#ref-G-805">G-805</a>], [<a href="#ref-G-807">G-807</a>], and [<a href="#ref-G-872">G-872</a>]. The
ASON terminology is defined in several Recommendations in the ASON
family such as [<a href="#ref-G-8080">G-8080</a>], [<a href="#ref-G-8081">G-8081</a>], [<a href="#ref-G-7713">G-7713</a>], [<a href="#ref-G-7714">G-7714</a>], and [<a href="#ref-G-7715">G-7715</a>].
The reader must be familiar with these documents before attempting to
apply the lexicography set out in this document.
<span class="h3"><a class="selflink" id="section-2.3" href="#section-2.3">2.3</a>. Common Terminology Sources</span>
The work in this document builds on the shared view of ASON
requirements and requirements expressed in [<a href="./rfc4139" title=""Requirements for Generalized MPLS (GMPLS) Signaling Usage and Extensions for Automatically Switched Optical Network (ASON)"">RFC4139</a>], [<a href="./rfc4258" title=""Requirements for Generalized Multi-Protocol Label Switching (GMPLS) Routing for the Automatically Switched Optical Network (ASON)"">RFC4258</a>], and
[<a href="./rfc4394" title=""A Transport Network View of the Link Management Protocol (LMP)"">RFC4394</a>].
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Lexicography</span>
<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. Network Presences</span>
<span class="h4"><a class="selflink" id="section-3.1.1" href="#section-3.1.1">3.1.1</a>. GMPLS Terms</span>
Transport node <Data Plane> is a logical network device that is
capable of originating and/or terminating of a data flow and/or
switching it on the route to its destination.
Controller <Control Plane> is a logical entity that models all
control plane intelligence (routing, traffic engineering (TE), and
signaling protocols, path computation, etc.). A single controller
can manage one or more transport nodes. Separate functions (such
as routing and signaling) may be hosted at distinct sites and
hence could be considered as separate logical entities referred
to, for example, as the routing controller, the signaling
controller, etc.
Label Switching Router (LSR) <Control & Data Planes> is a logical
combination of a transport node and the controller that manages
the transport node. Many implementations of LSRs collocate all
control plane and data plane functions associated with a transport
node within a single physical presence making the term LSR
concrete rather than logical.
In some instances, the term LSR may be applied more loosely to
indicate just the transport node or just the controller function
dependent on the context.
Node <Control & Data Planes> is a synonym for an LSR.
<span class="grey">Bryskin & Farrel Informational [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
Control plane network <Control Plane> is an IP network used for
delivery of control plane (protocol) messages exchanged by
controllers.
<span class="h4"><a class="selflink" id="section-3.1.2" href="#section-3.1.2">3.1.2</a>. ASON Terms</span>
A GMPLS transport node is an ASON network element.
A GMPLS controller is the set of ASON functional components
controlling a given ASON network element (or partition of a network
element). In ASON, this set of functional components may exist in
one place or multiple places.
A GMPLS node is the combination of an ASON network element (or
partition of a network element) and its associated control
components.
The GMPLS control plane network is the ASON Signaling Communication
Network (SCN). Note that both routing and signaling exchanges are
carried by the SCN.
<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>. Resources</span>
<span class="h4"><a class="selflink" id="section-3.2.1" href="#section-3.2.1">3.2.1</a>. GMPLS Terms</span>
Non-packet-based resource <Data Plane> is a channel of a certain
bandwidth that could be allocated in a network data plane of a
particular technology for the purpose of user traffic delivery.
Examples of non-packet-based resources are timeslots, lambda
channels, etc.
Packet-based resource <Data Plane> is an abstraction hiding the means
related to the delivery of traffic with particular parameters
(most importantly, bandwidth) with particular quality of service
(QoS) over PSC media. Examples of packet-based resources are
forwarding queues, schedulers, etc.
Layer Resource (Resource) <Data Plane>. A non-packet-based data
plane technology may yield resources in different network layers
(see <a href="#section-3.3">section 3.3</a>). For example, some TDM devices can operate with
VC-12 timeslots, some with VC-4 timeslots, and some with VC4-4c
timeslots. There are also multiple layers of packet-based
resources (i.e., one per label in the label stack). Therefore, we
define layer resource (or simply resource) irrespective of the
underlying data plane technology as a basic data plane construct.
It is defined by a combination of a particular data encoding type
<span class="grey">Bryskin & Farrel Informational [Page 5]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-6" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
and a switching/terminating bandwidth granularity. Examples of
layer resources are: PSC1, PSC4, ATM VP, ATM VC, Ethernet, VC-12,
VC-4, Lambda 10G, and Lambda 40G.
These three definitions give rise to the concept of Resource Type.
Although not a formal term, this is useful shorthand to identify how
and where a resource can be used dependent on the switching type,
data encoding type, and switching/terminating bandwidth granularity
(see <a href="#section-3.8">section 3.8</a>).
All other descriptions provided in this memo are tightly bound to the
resource.
<span class="h4"><a class="selflink" id="section-3.2.2" href="#section-3.2.2">3.2.2</a>. ASON Terms</span>
ASON terms for resource:
- In the context of link discovery and resource management
(allocation, binding into cross-connects, etc.), a GMPLS resource
is one end of a link connection.
- In the context of routing, path computation, and signaling, a GMPLS
resource is a link connection or trail termination.
Resource type is identified by a client CI (Characteristics
Information) that could be carried by the resource.
<span class="h3"><a class="selflink" id="section-3.3" href="#section-3.3">3.3</a>. Layers</span>
<span class="h4"><a class="selflink" id="section-3.3.1" href="#section-3.3.1">3.3.1</a>. GMPLS Terms</span>
Layer <Data Plane> is a set of resources of the same type that could
be used for establishing a connection or used for connectionless
data delivery.
Note. In GMPLS, the existence of non-blocking switching function in
a transport node in a particular layer is modeled explicitly as one
of the functions of the link interfaces connecting the transport node
to its data links.
A GMPLS layer is not the same as a GMPLS region. See <a href="#section-3.12">section 3.12</a>.
<span class="h4"><a class="selflink" id="section-3.3.2" href="#section-3.3.2">3.3.2</a>. ASON Terms</span>
A GMPLS layer is an ASON layer network.
<span class="grey">Bryskin & Farrel Informational [Page 6]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-7" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
<span class="h3"><a class="selflink" id="section-3.4" href="#section-3.4">3.4</a>. Labels</span>
<span class="h4"><a class="selflink" id="section-3.4.1" href="#section-3.4.1">3.4.1</a>. GMPLS Terms</span>
Label <Control Plane> is an abstraction that provides an identifier
for use in the control plane in order to identify a transport
plane resource.
<span class="h4"><a class="selflink" id="section-3.4.2" href="#section-3.4.2">3.4.2</a>. ASON Terms</span>
A GMPLS label is the portion of an ASON SNP name that follows the
SNPP name.
<span class="h3"><a class="selflink" id="section-3.5" href="#section-3.5">3.5</a>. Data Links</span>
<span class="h4"><a class="selflink" id="section-3.5.1" href="#section-3.5.1">3.5.1</a>. GMPLS Terms</span>
Unidirectional data link end <Data Plane> is a set of resources that
belong to the same layer and that could be allocated for the
transfer of traffic in that layer from a particular transport node
to the same neighboring transport node in the same direction. A
unidirectional data link end is connected to a transport node by
one or more link interfaces (see <a href="#section-3.6">section 3.6</a>).
Bidirectional data link end <Data Plane> is an association of two
unidirectional data link ends that exist in the same layer and
that could be used for the transfer of traffic in that layer
between a particular transport node and the same neighbor in both
directions. A bidirectional data link end is connected to a
transport node by one or more link interfaces (see <a href="#section-3.6">section 3.6</a>).
Unidirectional data link <Data Plane> is an association of two
unidirectional data link ends that exist in the same layer, that
are connected to two transport nodes adjacent in that layer, and
that could be used for the transfer of traffic between the two
transport nodes in one direction.
Bidirectional data link <Data Plane> is an association of two
bidirectional data link ends that exist in the same layer, that
are connected to two transport nodes adjacent in that layer, and
that could be used for the transfer of traffic between the two
transport nodes in both directions.
<span class="grey">Bryskin & Farrel Informational [Page 7]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-8" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
<span class="h4"><a class="selflink" id="section-3.5.2" href="#section-3.5.2">3.5.2</a>. ASON Terms</span>
A GMPLS unidirectional data link end is a collection of connection
points from the same client layer that are supported by a single
trail termination (access point).
A GMPLS data link is an ASON link supported by a single server trail.
<span class="h3"><a class="selflink" id="section-3.6" href="#section-3.6">3.6</a>. Link Interfaces</span>
<span class="h4"><a class="selflink" id="section-3.6.1" href="#section-3.6.1">3.6.1</a>. GMPLS Terms</span>
Unidirectional link interface <Data Plane> is an abstraction that
connects a transport node to a unidirectional data link end and
represents (hides) the data plane intelligence like switching,
termination, and adaptation in one direction. In GMPLS, link
interfaces are often referred to as "GMPLS interfaces" and it
should be understood that these are data plane interfaces and the
term does not refer to the ability of a control plane interface to
handle GMPLS protocols.
A single unidirectional data link end could be connected to a
transport node by multiple link interfaces with one of them, for
example, realizing switching function, while others realize the
function of termination/adaptation.
Bidirectional link interface <Data Plane> is an association of two or
more unidirectional link interfaces that connects a transport node
to a bidirectional data link end and represents the data plane
intelligence like switching, termination, and adaptation in both
directions.
Link interface type <Data Plane> is identified by the function the
interface provides. There are three distinct functions --
switching, termination, and adaptation; hence, there are three
types of link interface. Thus, when a Wavelength Division
Multiplexing (WDM) link can do switching for some lambda channels,
and termination and TDM OC48 adaptation for some other lambda
channels, we say that the link is connected to the transport node
by three interfaces each of a separate type: switching,
termination, and adaptation.
<span class="h4"><a class="selflink" id="section-3.6.2" href="#section-3.6.2">3.6.2</a>. ASON Terms</span>
A GMPLS interface is the set of trail termination and adaptation
functions between one or more server layer trails and a specific
client layer subnetwork (which commonly is a matrix in a network
element).
<span class="grey">Bryskin & Farrel Informational [Page 8]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-9" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
The GMPLS interface type may be identified by the ASON adapted client
layer, or by the terminated server layer, or a combination of the
two, depending on the context. In some cases, a GMPLS interface
comprises a set of ASON trail termination/adaptation functions, for
which some connection points are bound to trail terminations and
others to matrices.
<span class="h3"><a class="selflink" id="section-3.7" href="#section-3.7">3.7</a>. Connections</span>
<span class="h4"><a class="selflink" id="section-3.7.1" href="#section-3.7.1">3.7.1</a>. GMPLS Terms</span>
In GMPLS a connection is known as a Label Switched Path (LSP).
Unidirectional LSP (connection) <Data Plane> is a single resource or
a set of cross-connected resources of a particular layer that
could deliver traffic in that layer between a pair of transport
nodes in one direction.
Unidirectional LSP (connection) <Control Plane> is the signaling
state necessary to maintain a unidirectional data plane LSP.
Bidirectional LSP (connection) <Data Plane> is an association of two
unidirectional LSPs (connections) that could simultaneously
deliver traffic in a particular layer between a pair of transport
nodes in opposite directions.
In the context of GMPLS, both unidirectional constituents of a
bidirectional LSP (connection) take identical paths in terms of
data links, are provisioned concurrently, and require a single
(shared) control state.
Bidirectional LSP (connection) <Control Plane> is the signaling state
necessary to maintain a bidirectional data plane LSP.
LSP (connection) segment <Data Plane> is a single resource or a set
of cross-connected resources that constitutes a segment of an LSP
(connection).
<span class="h4"><a class="selflink" id="section-3.7.2" href="#section-3.7.2">3.7.2</a>. ASON Terms</span>
A GMPLS LSP (connection) is an ASON network connection.
A GMPLS LSP segment is an ASON serial compound link connection.
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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-10" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
<span class="h3"><a class="selflink" id="section-3.8" href="#section-3.8">3.8</a>. Switching, Termination, and Adaptation Capabilities</span>
<span class="h4"><a class="selflink" id="section-3.8.1" href="#section-3.8.1">3.8.1</a>. GMPLS Terms</span>
Switching capability <Data Plane> is a property (and defines a type)
of a link interface that connects a particular data link to a
transport node. This property/type characterizes the interface's
ability to cooperate with other link interfaces connecting data
links within the same layer to the same transport node for the
purpose of binding resources into cross-connects. Switching
capability is advertised as an attribute of the TE link local end
associated with the link interface.
Termination capability <Data Plane> is a property of a link interface
that connects a particular data link to a transport node. This
property characterizes the interface's ability to terminate
connections within the layer that the data link belongs to.
Adaptation capability <Data Plane> is a property of a link interface
that connects a particular data link to a transport node. This
property characterizes the interface's ability to perform a
nesting function -- to use a locally terminated connection that
belongs to one layer as a data link for some other layer.
The need for advertisement of adaptation and termination capabilities
within GMPLS has been recognized, and work is in progress to
determine how these will be advertised. It is likely that they will
be advertised as a single combined attribute, or as separate
attributes of the TE link local end associated with the link
interface.
<span class="h4"><a class="selflink" id="section-3.8.2" href="#section-3.8.2">3.8.2</a>. ASON Terms</span>
In ASON applications:
The GMPLS switching capability is a property of an ASON link end
representing its association with a matrix.
The GMPLS termination capability is a property of an ASON link end
representing potential binding to a termination point.
The GMPLS adaptation capability is a property of an ASON link end
representing potential adaptation to/from a client layer network.
<span class="grey">Bryskin & Farrel Informational [Page 10]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-11" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
<span class="h3"><a class="selflink" id="section-3.9" href="#section-3.9">3.9</a>. TE Links and FAs</span>
<span class="h4"><a class="selflink" id="section-3.9.1" href="#section-3.9.1">3.9.1</a>. GMPLS Terms</span>
TE link end <Control Plane> is a grouping for the purpose of
advertising and routing of resources of a particular layer.
Such a grouping allows for decoupling of path selection from
resource assignment. Specifically, a path could be selected in a
centralized way in terms of TE link ends, while the resource
assignment (resource reservation and label allocation) could be
performed in a distributed way during the connection setup. A TE
link end may reflect zero, one or more data link ends in the data
plane. A TE link end is associated with exactly one layer.
TE link <Control Plane> is a grouping of two TE link ends associated
with two neighboring transport nodes in a particular layer.
In contrast to a data link, which provides network flexibility in
a particular layer and, therefore, is a "real" topological
element, a TE link is a logical routing element. For example, an
LSP path is computed in terms of TE links (or more precisely, in
terms of TE link ends), while the LSP is provisioned over (that
is, resources are allocated from) data links.
Virtual TE link is a TE link associated with zero data links.
TE link end advertising <Control Plane>. A controller managing a
particular transport node advertises local TE link ends. Any
controller in the TE domain makes a TE link available for its
local path computation if it receives consistent advertisements of
both TE link ends. Strictly speaking, there is no such thing as
TE link advertising -- only TE link end advertising. TE link end
advertising may contain information about multiple switching
capabilities. This, however, should not be interpreted as
advertising of a multi-layer TE link end, but rather as joint
advertisement of ends of multiple parallel TE links, each
representing resources in a separate layer. The advertisement may
contain attributes shared by all TE links in the group (for
example, protection capabilities, Shared Risk Link Groups (SRLGs),
etc.), separate information related to each TE link (for example,
switching capability, data encoding, unreserved bandwidth, etc.)
as well as information related to inter-layer relationships of the
advertised resources (for example, termination and adaptation
capabilities) should the control plane decide to use them as the
termination points of higher-layer data links. These higher-layer
data links, however, are not real yet -- they are abstract until
the underlying connections are established in the lower layers.
<span class="grey">Bryskin & Farrel Informational [Page 11]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-12" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
LSPs created in lower layers for the purpose of providing data
links (extra network flexibility) in higher layers are called
hierarchical connections or LSPs (H-LSPs), or simply hierarchies.
LSPs created for the purpose of providing data links in the same
layer are called stitching segments. H-LSPs and stitching
segments could, but do not have to, be advertised as TE links.
Naturally, if they are advertised as TE links (LSPs advertised as
TE links are often referred to as TE-LSPs), they are made
available for path computations performed on any controller within
the TE domain into which they are advertised. H-LSPs and
stitching segments could be advertised either individually or in
TE bundles. An H-LSP or a stitching segment could be advertised
as a TE link either into the same or a separate TE domain compared
to the one within which it was provisioned.
A set of H-LSPs that is created (or could be created) in a
particular layer to provide network flexibility (data links) in
other layers is called a Virtual Network Topology (VNT). A single
H-LSP could provide several (more than one) data links (each in a
different layer).
Forwarding Adjacency (FA) <Control Plane> is a TE link that does not
require a direct routing adjacency (peering) between the
controllers managing its ends in order to guarantee control plane
connectivity (a control channel) between the controllers. An
example of an FA is an H-LSP or stitching segment advertised as a
TE link into the same TE domain within which it was dynamically
provisioned. In such cases, the control plane connectivity
between the controllers at the ends of the H-LSP/stitching segment
is guaranteed by the concatenation of control channels
interconnecting the ends of each of its constituents. In
contrast, an H-LSP or stitching segment advertised as a TE link
into a TE domain (different than one where it was provisioned)
generally requires a direct routing adjacency to be established
within the TE domain where the TE link is advertised in order to
guarantee control plane connectivity between the TE link ends.
Therefore, is not an FA.
<span class="h4"><a class="selflink" id="section-3.9.2" href="#section-3.9.2">3.9.2</a>. ASON Terms</span>
The ITU term for a TE link end is Subnetwork Point (SNP) pool (SNPP).
The ITU term for a TE link is SNPP link.
The ITU term for an H-LSP is trail.
<span class="grey">Bryskin & Farrel Informational [Page 12]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-13" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
<span class="h3"><a class="selflink" id="section-3.10" href="#section-3.10">3.10</a>. TE Domains</span>
<span class="h4"><a class="selflink" id="section-3.10.1" href="#section-3.10.1">3.10.1</a> GMPLS Terms</span>
TE link attribute is a parameter of the set of resources associated
with a TE link end that is significant in the context of path
computation.
Full TE visibility is a situation when a controller receives all
unmodified TE advertisements from every other controller in a
particular set of controllers.
Limited TE visibility is a situation when a controller receives
summarized TE information, or does not receive TE advertisements
from at least one of a particular set of controllers.
TE domain is a set of controllers each of which has full TE
visibility within the set.
TE database (TED) is a memory structure within a controller that
contains all TE advertisements generated by all controllers within
a particular TE domain.
Vertical network integration is a set of control plane mechanisms and
coordinated data plane mechanisms that span multiple layers. The
control plane mechanisms exist on one or more controllers and
operate either within a single control plane instance or between
control plane instances. The data plane mechanisms consist of
collaboration and adaptation between layers within a single
transport node.
Horizontal network integration is a set of control plane mechanisms
and coordinated data plane mechanisms that span multiple TE
domains within the same layer. The control plane mechanisms exist
on one or more controllers and operate either within a single
control plane instance or between control plane instances. The
data plane mechanisms consist of collaboration between TE domains.
<span class="h3"><a class="selflink" id="section-3.11" href="#section-3.11">3.11</a>. Component Links and Bundles</span>
<span class="h4"><a class="selflink" id="section-3.11.1" href="#section-3.11.1">3.11.1</a>. GMPLS Terms</span>
Component link end <Control Plane> is a grouping of resources of a
particular layer that is not advertised as an individual TE link
end. A component link end could represent one or more data link
ends or any subset of resources that belong to one or more data
link ends.
<span class="grey">Bryskin & Farrel Informational [Page 13]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-14" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
Component link <Control Plane> is a grouping of two or more component
link ends associated with neighboring transport nodes (that is,
directly interconnected by one or more data links) in a particular
layer. Component links are equivalent to TE links except that the
component link ends are not advertised separately.
TE bundle <Control Plane> is an association of several parallel (that
is, connecting the same pair of transport nodes) component links
whose attributes are identical or whose differences are
sufficiently negligible that the TE domain can view the entire
association as a single TE link. A TE bundle is advertised in the
same way as a TE link, that is, by representing the associated
component link ends as a single TE link end (TE bundle end) which
is advertised.
<span class="h3"><a class="selflink" id="section-3.12" href="#section-3.12">3.12</a>. Regions</span>
<span class="h4"><a class="selflink" id="section-3.12.1" href="#section-3.12.1">3.12.1</a>. GMPLS Terms</span>
TE region <Control Plane> is a set of one or more layers that are
associated with the same type of data plane technology. A TE
region is sometimes called an LSP region or just a region.
Examples of regions are: IP, ATM, TDM, photonic, fiber switching,
etc. Regions and region boundaries are significant for the
signaling sub-system of the control plane because LSPs are
signaled substantially differently (i.e., use different signaling
object formats and semantics) in different regions. Furthermore,
advertising, routing, and path computation could be performed
differently in different regions. For example, computation of
paths across photonic regions requires a wider set of constraints
(e.g., optical impairments, wavelength continuity, etc) and needs
to be performed in different terms (e.g., in terms of individual
resources -- lambda channels, rather than in terms of TE links)
compared to path computation in other regions like IP or TDM.
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Guidance on the Application of this Lexicography</span>
As discussed in the introduction to this document, this lexicography
is intended to bring the concepts and terms associated with GMPLS
into the context of the ITU-T's ASON architecture. Thus, it should
help those familiar with ASON to see how they may use the features
and functions of GMPLS in order to meet the requirements of an ASON.
For example, service providers wishing to establish a protected end-
to-end service might read [<a href="#ref-SEG-PROT" title=""GMPLS Based Segment Recovery"">SEG-PROT</a>] and [<a href="#ref-E2E-PROT" title=""RSVP-TE Extensions in support of End-to-End Generalized Multi-Protocol Label Switching (GMPLS)-based Recovery"">E2E-PROT</a>] and wish to
understand how the GMPLS terms used relate to the ASON architecture
so that they can confirm that they will satisfy their requirements.
<span class="grey">Bryskin & Farrel Informational [Page 14]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-15" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
This lexicography should not be used in order to obtain or derive
definitive definitions of GMPLS terms. To obtain definitions of
GMPLS terms that are applicable across all GMPLS architectural
models, the reader should refer to the RFCs listed in the references
sections of this document. [<a href="./rfc3945" title=""Generalized Multi-Protocol Label Switching (GMPLS) Architecture"">RFC3945</a>] provides an overview of the
GMPLS architecture and should be read first.
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Management Considerations</span>
Both GMPLS and ASON networks require management. Both GMPLS and ASON
specifications include considerable efforts to provide operator
control and monitoring, as well as Operations and Management (OAM)
functionality.
These concepts are, however, out of scope of this document.
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Security Considerations</span>
Security is also a significant requirement of both GMPLS and ASON
architectures.
Again, however, this informational document is intended only to
provide a lexicography, and the security concerns are, therefore, out
of scope.
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. Acknowledgements</span>
The authors would like to thank participants in the IETF's CCAMP
working group and the ITU-T's Study Group 15 for their help in
producing this document. In particular, all those who attended the
Study Group 15 Question 14 Interim Meeting in Holmdel, New Jersey
during January 2005. Further thanks to all participants of Study
Group 15 Questions 12 and 14 who have provided valuable discussion,
feedback and suggested text.
Many thanks to Ichiro Inoue for his useful review and input, and to
Scott Brim and Dimitri Papadimitriou for lengthy and constructive
discussions. Ben Mack-Crane and Jonathan Sadler provided very
helpful reviews and discussions of ASON terms. Thanks to Deborah
Brungard and Kohei Shiomoto for additional review comments.
<span class="grey">Bryskin & Farrel Informational [Page 15]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-16" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. Normative References</span>
[<a id="ref-RFC3945">RFC3945</a>] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", <a href="./rfc3945">RFC 3945</a>, October
2004.
[<a id="ref-RFC4201">RFC4201</a>] Kompella, K., Rekhter, Y., and L. Berger, "Link
Bundling in MPLS Traffic Engineering (TE)", <a href="./rfc4201">RFC</a>
<a href="./rfc4201">4201</a>, October 2005.
[<a id="ref-RFC4202">RFC4202</a>] Kompella, K. and Y. Rekhter, "Routing Extensions in
Support of Generalized Multi-Protocol Label
Switching (GMPLS)", <a href="./rfc4202">RFC 4202</a>, October 2005.
[<a id="ref-RFC4204">RFC4204</a>] Lang, J., Ed., "Link Management Protocol (LMP)", <a href="./rfc4204">RFC</a>
<a href="./rfc4204">4204</a>, October 2005.
[<a id="ref-RFC4206">RFC4206</a>] Kompella, K. and Y. Rekhter, "Label Switched Paths
(LSP) Hierarchy with Generalized Multi-Protocol
Label Switching (GMPLS) Traffic Engineering (TE)",
<a href="./rfc4206">RFC 4206</a>, October 2005.
<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>. Informative References</span>
[<a id="ref-RFC3471">RFC3471</a>] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
<a href="./rfc3471">RFC 3471</a>, January 2003.
[<a id="ref-RFC3473">RFC3473</a>] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
<a href="./rfc3471">RFC 3471</a>, January 2003.
[<a id="ref-RFC4139">RFC4139</a>] Papadimitriou, D., Drake, J., Ash, J., Farrel, A.,
and L. Ong, "Requirements for Generalized MPLS
(GMPLS) Signaling Usage and Extensions for
Automatically Switched Optical Network (ASON)", <a href="./rfc4139">RFC</a>
<a href="./rfc4139">4139</a>, July 2005.
[<a id="ref-RFC4203">RFC4203</a>] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF
Extensions in Support of Generalized Multi-Protocol
Label Switching (GMPLS)", <a href="./rfc4203">RFC 4203</a>, October 2005.
[<a id="ref-RFC4205">RFC4205</a>] Kompella, K., Ed. and Y. Rekhter, Ed., "Intermediate
System to Intermediate System (IS-IS) Extensions in
Support of Generalized Multi-Protocol Label
Switching (GMPLS)", <a href="./rfc4205">RFC 4205</a>, October 2005.
<span class="grey">Bryskin & Farrel Informational [Page 16]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-17" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
[<a id="ref-RFC4258">RFC4258</a>] Brungard, D., Ed., "Requirements for Generalized
Multi-Protocol Label Switching (GMPLS) Routing for
the Automatically Switched Optical Network (ASON)",
<a href="./rfc4258">RFC 4258</a>, November 2005.
[<a id="ref-RFC4394">RFC4394</a>] Fedyk, D., Aboul-Magd, O., Brungard, D., Lang, J.,
and D. Papadimitriou, "A Transport Network View of
the Link Management Protocol (LMP)", <a href="./rfc4394">RFC 4394</a>,
February 2006.
[<a id="ref-E2E-PROT">E2E-PROT</a>] Lang, J., Ed., Rekhter, Y., Ed., and D.
Papadimitriou, D., Ed., "RSVP-TE Extensions in
support of End-to-End Generalized Multi-Protocol
Label Switching (GMPLS)-based Recovery", Work in
Progress, April 2005.
[<a id="ref-SEG-PROT">SEG-PROT</a>] Berger, L., Bryskin, I., Papadimitriou, D., and A.
Farrel, "GMPLS Based Segment Recovery", Work in
Progress, May 2005.
For information on the availability of the following documents,
please see <a href="http://www.itu.int">http://www.itu.int</a>.
[<a id="ref-G-8080">G-8080</a>] ITU-T Recommendation G.8080/Y.1304, Architecture for
the automatically switched optical network (ASON).
[<a id="ref-G-805">G-805</a>] ITU-T Recommendation G.805 (2000), Generic
functional architecture of transport networks.
[<a id="ref-G-807">G-807</a>] ITU-T Recommendation G.807/Y.1302 (2001),
Requirements for the automatic switched transport
network (ASTN).
[<a id="ref-G-872">G-872</a>] ITU-T Recommendation G.872 (2001), Architecture of
optical transport networks.
[<a id="ref-G-8081">G-8081</a>] ITU-T Recommendation G.8081 (2004), Terms and
definitions for Automatically Switched Optical
Networks (ASON).
[<a id="ref-G-7713">G-7713</a>] ITU-T Recommendation G.7713 (2001), Distributed Call
and Connection Management.
[<a id="ref-G-7714">G-7714</a>] ITU-T Recommendation G.7714 Revision (2005),
Generalized automatic discovery techniques.
<span class="grey">Bryskin & Farrel Informational [Page 17]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-18" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
[<a id="ref-G-7715">G-7715</a>] ITU-T Recommendation G.7715 (2002), Architecture and
Requirements for the Automatically Switched Optical
Network (ASON).
Authors' Addresses
Igor Bryskin
Independent Consultant
EMail: i_bryskin@yahoo.com
Adrian Farrel
Old Dog Consulting
Phone: +44 (0) 1978 860944
EMail: adrian@olddog.co.uk
<span class="grey">Bryskin & Farrel Informational [Page 18]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-19" ></span>
<span class="grey"><a href="./rfc4397">RFC 4397</a> GMPLS ASON Lexicography February 2006</span>
Full Copyright Statement
Copyright (C) The Internet Society (2006).
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Bryskin & Farrel Informational [Page 19]
</pre>
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