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RFC 4394 - A Transport Network View of the Link Management Proto

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Network Working Group                                           D. Fedyk
Request for Comments: 4394                                 O. Aboul-Magd
Category: Informational                                  Nortel Networks
                                                             D. Brungard
                                                                 J. Lang
                                                             Sonos, Inc.
                                                        D. Papadimitriou
                                                           February 2006

    A Transport Network View of the Link Management Protocol (LMP)

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).


   The Link Management Protocol (LMP) has been developed as part of the
   Generalized MPLS (GMPLS) protocol suite to manage Traffic Engineering
   (TE) resources and links.  The GMPLS control plane (routing and
   signaling) uses TE links for establishing Label Switched Paths
   (LSPs).  This memo describes the relationship of the LMP procedures
   to 'discovery' as defined in the International Telecommunication
   Union (ITU-T), and ongoing ITU-T work.  This document provides an
   overview of LMP in the context of the ITU-T Automatically Switched
   Optical Networks (ASON) and transport network terminology and relates
   it to the ITU-T discovery work to promote a common understanding for
   progressing the work of IETF and ITU-T.

Table of Contents

   1. Introduction ....................................................2
   2. ASON Terminology and Abbreviations Related to Discovery .........3
      2.1. Terminology ................................................3
      2.2. Abbreviations ..............................................4
   3. Transport Network Architecture ..................................5
      3.1. G.8080 Discovery Framework .................................7
   4. Discovery Technologies ..........................................9
      4.1. Generalized Automatic Discovery Techniques G.7714 ..........9
      4.2. LMP and G.8080 Terminology Mapping .........................9
           4.2.1. TE Link Definition and Scope .......................12
      4.3. LMP and G.8080 Discovery Relationship .....................13
      4.4. Comparing LMP and G.8080 ..................................14
   5. Security Considerations ........................................15
   6. Informative References .........................................15
   7. Acknowledgements ...............................................16

1.  Introduction

   The GMPLS control plane consists of several building blocks as
   described in [RFC3945].  The building blocks include signaling,
   routing, and link management for establishing LSPs.  For scalability
   purposes, multiple physical resources can be combined to form a
   single TE link for the purposes of path computation and GMPLS control
   plane signaling.

   As manual provisioning and management of these links are impractical
   in large networks, LMP was specified to manage TE links.  Two
   mandatory management capabilities of LMP are control channel
   management and TE link property correlation.  Additional optional
   capabilities include verifying physical connectivity and fault
   management.  [LMP] defines the messages and procedures for GMPLS TE
   link management.  [LMP-TEST] defines SONET/SDH-specific messages and
   procedures for link verification.

   ITU-T Recommendation G.8080 Amendment 1 [G.8080] defines control
   plane discovery as two separate processes; one process occurs within
   the transport plane space and the other process occurs within the
   control plane space.

   The ITU-T has developed Recommendation G.7714, "Generalized automatic
   discovery techniques" [G.7714], defining the functional processes and
   information exchange related to transport plane discovery aspects,
   i.e., layer adjacency discovery and physical media adjacency
   discovery.  Specific methods and protocols are not defined in
   Recommendation G.7714.  ITU-T Recommendation G.7714.1, "Protocol for
   automatic discovery in SDH and OTN networks" [G.7714.1], defines a

   protocol and procedure for transport plane layer adjacency discovery
   (e.g., discovering the transport plane layer endpoint relationships
   and verifying their connectivity).  The ITU-T is currently working to
   extend discovery to control plane aspects providing detail on a
   discovery framework architecture in G.8080 and a new Recommendation
   on "Control plane initial establishment, reconfiguration".

2.  ASON Terminology and Abbreviations Related to Discovery

   ITU-T Recommendation G.8080 Amendment 1 [G.8080] and ITU-T
   Recommendation G.7714 [G.7714] provide definitions and mechanisms
   related to transport plane discovery.

   Note that in the context of this work, "Transport" relates to the
   data plane (sometimes called the transport plane or the user plane)
   and does not refer to the transport layer (layer 4) of the OSI seven
   layer model, nor to the concept of transport intended by protocols
   such as the Transmission Control Protocol (TCP).

   Special care must be taken with the acronym "TCP", which within the
   context of the rest of this document means "Termination Connection
   Point" and does not indicate the Transmission Control Protocol.

2.1.  Terminology

   The reader is assumed to be familiar with the terminology in [LMP]
   and [LMP-TEST].  The following ITU-T terminology/abbreviations are
   used in this document:

   Connection Point (CP): A "reference point" that consists of a pair of
   co-located "unidirectional connection points" and therefore
   represents the binding of two paired bidirectional "connections".

   Connection Termination Point (CTP): A connection termination point
   represents the state of a CP [M.3100].

   Characteristic Information:  Signal with a specific format, which is
   transferred on "network connections".  The specific formats will be
   defined in the technology-specific recommendations.  For trails, the
   Characteristic Information is the payload plus the overhead.  The
   information transferred is characteristic of the layer network.

   Link: A subset of ports at the edge of a subnetwork or access group
   that are associated with a corresponding subset of ports at the edge
   of another subnetwork or access group.

   Link Connection (LC): A transport entity that transfers information
   between ports across a link.

   Network Connection (NC): A concatenation of link and subnetwork

   Subnetwork: A set of ports that are available for the purpose of
   routing 'characteristic information'.

   Subnetwork Connection (SNC): A flexible connection that is set up and
   released using management or control plane procedures.

   Subnetwork Point (SNP): SNP is an abstraction that represents an
   actual or potential underlying connection point (CP) or termination
   connection point (TCP) for the purpose of control plane

   Subnetwork Point Pool (SNPP): A set of SNPs that are grouped together
   for the purpose of routing.

   Termination Connection Point (TCP): A reference point that represents
   the output of a Trail Termination source function or the input to a
   Trail Termination sink function.  A network connection represents a
   transport entity between TCPs.

   Trail Termination source/sink function: A "transport processing
   function" that accepts the characteristic information of the layer
   network at its input, removes the information related to "trail"
   monitoring, and presents the remaining information at its output.

   Unidirectional Connection: A "transport entity" that transfers
   information transparently from input to output.

   Unidirectional Connection Point: A "reference point" that represents
   the binding of the output of a "unidirectional connection" to the
   input of another "unidirectional connection".

2.2.  Abbreviations

   LMP: Link Management Protocol

   OTN: Optical Transport Network

   PDH: Plesiosynchronous Digital Hierarchy

   SDH: Synchronous Digital Hierarchy

   SONET: Synchronous Optical Network

3.  Transport Network Architecture

   A generic functional architecture for transport networks is defined
   in International Telecommunication Union (ITU-T) Recommendation
   [G.805].  This recommendation describes the functional architecture
   of transport networks in a technology-independent way.  This
   architecture forms the basis for a set of technology-specific
   architectural recommendations for transport networks (e.g., SDH, PDH,
   OTN, etc.).

   The architecture defined in G.805 is designed using a layered model
   with a client-server relationship between layers.  The architecture
   is recursive in nature; a network layer is both a server to the
   client layer above it and a client to the server layer below it.
   There are two basic building blocks defined in G.805: "subnetworks"
   and "links".  A subnetwork is defined as a set of ports that are
   available for the purpose of routing "characteristic information".  A
   link consists of a subset of ports at the edge of one subnetwork (or
   "access group") and is associated with a corresponding subset of
   ports at the edge of another subnetwork or access group.

   Two types of connections are defined in G.805: link connection (LC)
   and subnetwork connection (SNC).  A link connection is a fixed and
   inflexible connection, while a subnetwork connection is flexible and
   is set up and released using management or control plane procedures.
   A network connection is defined as a concatenation of subnetwork and
   link connections.  Figure 1 illustrates link and subnetwork

                  (++++++++)              (++++++++)
                 (   SNC    )   LC       (   SNC    )
                 (          ) CP      CP (          )
                  (++++++++)              (++++++++)

                  subnetwork              subnetwork

                Figure 1: Subnetwork and Link Connections

   G.805 defines a set of reference points for the purpose of
   identification in both the management and the control planes.  These
   identifiers are NOT required to be the same.  A link connection or a
   subnetwork connection is delimited by connection points (CPs).  A
   network connection is delimited by a termination connection point
   (TCP).  A link connection in the client layer is represented by a
   pair of adaptation functions and a trail in the server layer network.
   A trail represents the transfer of monitored adapted characteristics
   information of the client layer network between access points (APs).

   A trail is delimited by two access points, one at each end of the
   trail.  Figure 2 shows a network connection and its relationship with
   link and subnetwork connections.  Figure 2 also shows the CP and TCP
   reference points.

                |<-------Network Connection---------->|
                |                                     |
                | (++++++++)              (++++++++)  |
                |(   SNC    )   LC       (   SNC    ) |
              TCP(          )| CP    CP |(          )TCP
                  (++++++++) |          | (++++++++)
                             |          |
                             |  Trail   |
                             |          |
                            ---        ---
                            \ /        \ /
                             -          -
                          AP 0          0 AP
                             |          |

     Figure 2: Network Connection with Link and Subnetwork Connections

   For management plane purposes, the G.805 reference points are
   represented by a set of management objects described in ITU-T
   Recommendation M.3100 [M.3100].  Connection termination points (CTPs)
   and trail termination points (TTPs) are the management plane objects
   for CP and TCP, respectively.

   In the same way as in M.3100, the transport resources in G.805 are
   identified for the purposes of the control plane by entities suitable
   for connection control.  G.8080 introduces the reference architecture
   for the control plane of the Automatically Switched Optical Networks
   (ASONs).  G.8080 introduces a set of reference points relevant to the
   ASON control plane and their relationship to the corresponding points
   in the transport plane.  A subnetwork point (SNP) is an abstraction
   that represents an actual or potential underlying CP or an actual or
   potential TCP.  A set of SNPs that are grouped together for the
   purpose of routing is called SNP pool (SNPP).  Similar to LC and SNC,
   the SNP-SNP relationship may be static and inflexible (this is
   referred to as an SNP link connection), or it can be dynamic and
   flexible (this is referred to as an SNP subnetwork connection).

3.1.  G.8080 Discovery Framework

   G.8080 provides a reference control plane architecture based on the
   descriptive use of functional components representing abstract
   entities and abstract component interfaces.  The description is
   generic, and no particular physical partitioning of functions is
   implied.  The input/output information flows associated with the
   functional components serve for defining the functions of the
   components and are considered to be conceptual, not physical.
   Components can be combined in different ways, and the description is
   not intended to limit implementations.  Control plane discovery is
   described in G.8080 by using three components: Discovery Agent (DA),
   Termination and Adaptation Performer (TAP), and Link Resource Manager

   The objective of the discovery framework in G.8080 is to establish
   the relationship between CP-CP link connections (transport plane) and
   SNP-SNP link connections (control plane).  The fundamental
   characteristics of G.8080 discovery framework is the functional
   separation between the control and the transport plane discovery
   processes and name spaces.  From G.8080: "This separation allows
   control plane names to be completely separate from transport plane
   names, and completely independent of the method used to populate the
   DAs with those transport names.  In order to assign an SNP-SNP link
   connection to an SNPP link, it is only necessary for the transport
   name for the link connection to exist".  Thus, it is possible to
   assign link connections to the control plane without the link
   connection being physically connected.

   Discovery encompasses two separate processes: (1) transport plane
   discovery, i.e., CP-to-CP and TCP-to-TCP connectivity; and (2)
   control plane discovery, i.e., SNP-to-SNP and SNPP links.

   G.8080 Amendment 1 defines the Discovery Agent (DA) as the entity
   responsible for discovery in the transport plane.  The DA operates in
   the transport name space only and in cooperation with the Termination
   and Adaptation Performer (TAP), provides the separation between that
   space and the control plane names.  A local DA is only aware of the
   CPs and TCPs that are assigned to it.  The DA holds the CP-CP link
   connection in the transport plane to enable SNP-SNP link connections
   to be bound to them at a later time by the TAP.  The CP-CP
   relationship may be discovered (e.g., per G.7714.1) or provided by a
   management system.

   Control plane discovery takes place entirely within the control plane
   name space (SNPs).  The Link Resource Manager (LRM) holds the SNP-SNP
   binding information necessary for the control plane name of the link
   connection, while the termination adaptation performer (TAP) holds

   the relation between the control plane name (SNP) and the transport
   plane name (CP) of the resource.  Figure 3 shows the relationship and
   the different entities for transport and control discoveries.

          LRM                             LRM
        +-----+ holds SNP-SNP Relation  +-----+
        |     |-------------------------|     |
        +-----+                         +-----+
           |                               |
           v                               v
        +-----+                         +-----+
        |  o  | SNPs in SNPP            |  o  |
        |     |                         |     |
        |  o  |                         |  o  |
        |     |                         |     |
        |  o  |                         |  o  |
        +-----+                         +-----+
           |                               |
           v                               v        Control Plane
        +-----+                         +-----+        Discovery
        |     | Termination and         |     |
        |     | Adaptation Performer    |     |
        +-----+       (TAP)             +-----+     Transport Plane
          |   \                           /  |          Discovery
          |    \                         /   |
          |  +-----+                +-----+  |
          |  | DA  |                |  DA |  |
          |  |     |                |     |  |
          |  +-----+                +-----+  |
          | /                              \ |
          V/                                \V
          O  CP (Transport Name)             O   CP (Transport Name)

      Figure 3: Discovery in the Control and the Transport Planes

4.  Discovery Technologies

4.1.  Generalized Automatic Discovery Techniques G.7714

   Generalized automatic discovery techniques are described in G.7714 to
   aid resource management and routing for G.8080.  The term routing
   here is described in the transport context of routing connections in
   an optical network as opposed to the routing context typically
   associated in packet networks.

   G.7714 is concerned with two types of discovery:

   - Layer adjacency discovery
   - Physical media adjacency discovery

   Layer adjacency discovery can be used to correlate physical
   connections with management configured attributes.  Among other
   features this capability allows reduction in configuration and the
   detection of mis-wired equipment.

   Physical media adjacency discovery is a process that allows the
   physical testing of the media for the purpose of inventory capacity
   and verifying the port characteristics of physical media adjacent

   G.7714 does not specify specific protocols but rather the type of
   techniques that can be used.  G.7714.1 specifies a protocol for layer
   adjacency with respect to SDH and OTN networks for layer adjacency
   discovery.  A GMPLS method for layer discovery using elements of LMP
   is included in this set of procedures.

   An important point about the G.7714 specification is that it
   specifies a discovery mechanism for optical networks but not
   necessarily how the information will be used.  It is intended that
   the transport management plane or a transport control plane may
   subsequently make use of the discovered information.

4.2.  LMP and G.8080 Terminology Mapping

   GMPLS is a set of IP-based protocols, including LMP, providing a
   control plane for multiple data plane technologies, including
   optical/transport networks and their resources (i.e., wavelengths,
   timeslots, etc.) and without assuming any restriction on the control
   plane architecture (see [RFC3945]).  On the other hand, G.8080
   defines a control plane reference architecture for optical/transport
   networks without any restriction on the control plane implementation.
   Being developed in separate standards forums, and with different
   scopes, they use different terms and definitions.

   Terminology mapping between LMP and ASON (G.805/G.8080) is an
   important step towards the understanding of the two architectures and
   allows for potential cooperation in areas where cooperation is
   possible.  To facilitate this mapping, we differentiate between the
   two types of data links in LMP.  According to LMP, a data link may be
   considered by each node that it terminates on as either a 'port' or a
   'component link'.  The LMP notions of port and component link are
   supported by the G.805/G.8080 architecture.  G.8080's variable
   adaptation function is broadly equivalent to LMP's component link,
   i.e., a single server-layer trail dynamically supporting different
   multiplexing structures.  Note that when the data plane delivers its
   own addressing space, LMP Interface_IDs and Data Links IDs are used
   as handles by the control plane to the actual CP Name and CP-to-CP
   Name, respectively.

   The terminology mapping is summarized in the following table: Note
   that the table maps ASON terms to GMPLS terms that refer to
   equivalent objects, but in many cases there is not a one-to-one
   mapping.  Additional information beyond discovery terminology can be
   found in [LEXICO].

   | ASON Terms     | GMPLS/LMP Terms    | GMPLS/LMP Terms   |
   |                | Port               | Component Link    |
   | CP             | TE Resource;       | TE Resource;      |
   |                | Interface (Port)   | Interface.        |
   |                |                    |(Comp. link)       |
   | CP Name        | Interface ID       | Interface ID(s)   |
   |                | no further sub-    | resources (such as|
   |                | division for(label)| timeslots, etc.)  |
   |                | resource allocation| on this interface |
   |                |                    | are identified by |
   |                |                    | set of labels     |
   | CP-to-CP Link  | Data Link          | Data Link         |
   | CP-to-CP Name  | Data Link ID       | Data Link ID      |
   | SNP            | TE Resource        | TE Resource       |
   | SNP Name       | Link ID            | Link ID           |
   | SNP LC         | TE Link            | TE Link           |
   | SNP LC Name    | TE Link ID         | TE Link ID        |
   | SNPP           | TE Link End        | TE Link End       |
   |                | (Port)             | (Comp. Link)      |
   | SNPP Name      | Link ID            | Link ID           |
   | SNPP Link      | TE Link            | TE Link           |
   | SNPP Link Name | TE Link ID         | TE Link ID        |

   where composite identifiers are:

   - Data Link ID: <Local Interface ID; Remote Interface ID>
   - TE Link ID:   <Local Link ID; Remote Link ID>

   Composite Identifiers are defined in the RFC 4204 [LMP].  LMP
   discovers data links and identifies them by the pair of local and
   remote interface IDs.  TE links are composed of data links or
   component TE links.  TE links are similarly identified by pair of
   local and remote link ID.

4.2.1.  TE Link Definition and Scope

   In the table, TE link/resource is equated with the concept of SNP,
   SNP LC, SNPP, and SNPP link.  The definition of the TE link is broad
   in scope, and it is useful to repeat it here.  The original
   definition appears in [GMPLS-RTG]:

   "A TE link is a logical construct that represents a way to group/map
   the information about certain physical resources (and their
   properties) that interconnects LSRs into the information that is used
   by Constrained SPF for GMPLS path computation, and GMPLS signaling".

   While this definition is concise, it is probably worth pointing out
   some of the implications of the definition.

   A component of the TE link may follow different paths between the
   pair of LSRs.  For example, a TE link comprising multiple STS-3cs,
   the individual STS-3cs component links may take identical or
   different physical (OC-3 and/or OC-48) paths between LSRs.

   The TE link construct is a logical construction encompassing many
   layers in networks [RFC3471].  A TE link can represent either
   unallocated potential or allocated actual resources.  Further
   allocation is represented by bandwidth reservation, and the resources
   may be real or, in the case of packets, virtual to allow for
   overbooking or other forms of statistical multiplexing schemes.

   Since TE links may represent large numbers of parallel resources,
   they can be bundled for efficient summarization of resource capacity.
   Typically, bundling represents a logical TE link resource at a
   particular Interface Switching Capability.  Once TE link resources
   are allocated, the actual capacity may be represented as LSP
   hierarchical (tunneled) TE link capability in another logical TE link

   TE links also incorporate the notion of a Forwarding Adjacency (FA)
   and Interface Switching Capability [RFC3945].  The FA allows
   transport resources to be represented as TE links.  The Interface
   Switching Capability specifies the type of transport capability such
   as Packet Switch Capable (PSC), Layer-2 Switch Capable (L2SC), Time-
   Division Multiplex (TDM), Lambda Switch Capable (LSC), and Fiber-
   Switch Capable (FSC).

   A TE link between GMPLS-controlled optical nodes may consist of a
   bundled TE link, which itself consists of a mix of point-to-point
   component links [BUNDLE].  A TE link is identified by the tuple (link
   Identifier (32-bit number), Component link Identifier (32-bit
   number), and generalized label (media specific)).

4.3.  LMP and G.8080 Discovery Relationship

   LMP currently consists of four primary procedures, of which the first
   two are mandatory and the last two are optional:

         1.  Control channel management
         2.  Link property correlation
         3.  Link verification
         4.  Fault management

   LMP procedures that are relevant to G.8080 control plane discovery
   are control channel management, link property correlation, and link
   verification.  Key to understanding G.8080 discovery aspects in
   relation to [LMP] is that LMP procedures are specific for an IP-based
   control plane abstraction of the transport plane.

   LMP control channel management is used to establish and maintain
   control channel connectivity between LMP adjacent nodes.  In GMPLS,
   the control channels between two adjacent nodes are not required to
   use the same physical medium as the TE links between those nodes.
   The control channels that are used to exchange the GMPLS control
   plane information exist independently of the TE links they manage
   (i.e., control channels may be in-band or out-of-band, provided the
   associated control points terminate the LMP packets).  The Link
   Management Protocol [LMP] was designed to manage TE links,
   independently of the physical medium capabilities of the data links.

   Link property correlation is used to aggregate multiple data links
   into a single TE link and to synchronize the link properties.

   Link verification is used to verify the physical connectivity of the
   data links and verify the mapping of the Interface-ID to Link-ID (CP
   to SNP).  The local-to-remote associations can be obtained using a
   priori knowledge or using the link verification procedure.

   Fault management is primarily used to suppress alarms and to localize
   failures.  It is an optional LMP procedure; its use will depend on
   the specific technology's capabilities.

   [LMP] supports distinct transport and control plane name spaces with
   the (out-of-band) TRACE object (see [LMP-TEST]).  The LMP TRACE
   object allows transport plane names to be associated with interface
   identifiers [LMP-TEST].

   Aspects of LMP link verification appear similar to G.7714.1
   discovery; however, the two procedures are different.  G.7714.1
   provides discovery of the transport plane layer adjacencies.  It
   provides a generic procedure to discover the connectivity of two

   endpoints in the transport plane.  On the other hand, the LMP link
   verification procedure is a control-plane-driven procedure and
   assumes either (1) a priori knowledge of the associated data plane's
   local and remote endpoint connectivity and Interface_IDs (e.g., via
   management plane or use of G.7714.1), or (2) support of the remote
   node for associating the data interface being verified with the
   content of the TRACE object (inferred mapping).  For SONET/SDH
   transport networks, LMP verification uses the SONET/SDH Trail Trace
   identifier (see [G.783]).

   G.7714.1 supports the use of transport plane discovery independent of
   the platform using the capability.  Furthermore, G.7714.1 specifies
   the use of a Discovery Agent that could be located in an external
   system and the need to support the use of text-oriented man-machine
   language to provide the interface.  Therefore, G.7714.1 limits the
   discovery messages to printable characters defined by [T.50] and
   requires Base64 encoding for the TCP-ID and DA ID.  External name-
   servers may be used to resolve the G.7714.1 TCP name, allowing the
   TCP to have an IP, Network Service Access Protocol (NSAP), or any
   other address format.  On the other hand, LMP is based on the use of
   an IP-based control plane, and the LMP interface ID uses IPv4, IPv6,
   or unnumbered interface IDs.

4.4.  Comparing LMP and G.8080

   LMP exists to support GMPLS TE resource and TE link discovery.  In
   section 4.2.1, we elaborated on the definition of the TE link.  LMP
   enables the aspects of TE links to be discovered and reported to the
   control plane, more specifically, the routing plane.  G.8080 and
   G.7714 are agnostic to the type of control plane and discovery
   protocol used.  LMP is a valid realization of a control plane
   discovery process under a G.8080 model.

   G.7714 specifies transport plane discovery with respect to the
   transport layer CTPs or TCPs using ASON conventions and naming for
   the elements of the ASON control plane and the ASON management plane.
   This discovery supports a centralized management model of
   configuration as well as a distributed control plane model; in other
   words, discovered items can be reported to the management plane or
   the control plane.  G.7714.1 provides one realization of a transport
   plane discovery process.

   Today, LMP and G.7714, G7714.1 are defined in different standards
   organizations.  They have evolved out of different naming schemes and
   architectural concepts.  Whereas G.7714.1 supports a transport plane
   layer adjacency connectivity verification that can be used by a

   control plane or a management plane, LMP is a control plane procedure
   for managing GMPLS TE links (GMPLS's control plane representation of
   the transport plane connections).

5.  Security Considerations

   Since this document is purely descriptive in nature, it does not
   introduce any security issues.

   G.8080 and G.7714/G.7714.1 provide security as associated with the
   Data Communications Network on which they are implemented.

   LMP is specified using IP, which provides security mechanisms
   associated with the IP network on which it is implemented.

6.  Informative References

   [LMP]       Lang, J., "Link Management Protocol (LMP)", RFC 4204,
               October 2005.

   [LMP-TEST]  Lang, J. and D. Papadimitriou, "Synchronous Optical
               Network (SONET)/Synchronous Digital Hierarchy (SDH)
               Encoding for Link Management Protocol (LMP) Test
               Messages", RFC 4207, October 2005.

   [RFC3945]   Mannie, E., "Generalized Multi-Protocol Label Switching
               (GMPLS) Architecture", RFC 3945, October 2004.

   [RFC3471]   Berger, L., "Generalized Multi-Protocol Label Switching
               (GMPLS) Signaling Functional Description", RFC 3471,
               January 2003.

   [GMPLS-RTG] Kompella, K. and Y. Rekhter, "Routing Extensions in
               Support of Generalized Multi-Protocol Label Switching
               (GMPLS)", RFC 4202, October 2005.

   [HIER]      Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
               Hierarchy with Generalized Multi-Protocol Label Switching
               (GMPLS) Traffic Engineering (TE)", RFC 4206, October

   [BUNDLE]    Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling
               in MPLS Traffic Engineering (TE)", RFC 4201, October

   [LEXICO]    Bryskin, I. and A. Farrel, "A Lexicography for the
               Interpretation of Generalized Multiprotocol Label
               Switching (GMPLS) Terminology within The Context of the
               ITU-T's Automatically Switched Optical Network (ASON)
               Architecture", Work in Progress, January 2006.

   For information on the availability of the ITU-T documents, please
   see http://www.itu.int.

   [G.783]     ITU-T G.783 (2004), Characteristics of synchronous
               digital hierarchy (SDH) equipment functional blocks.

   [G.805]     ITU-T G.805 (2000), Generic functional architecture of
               transport networks.

   [G.7714]    ITU-T G.7714/Y.1705 (2001), Generalized automatic
               discovery techniques.

   [G.7714.1]  ITU-T G.7714.1/Y.1705.1 (2003), Protocol for automatic
               discovery in SDH and OTN networks.

   [G.8080]    ITU-T G.8080/Y.1304 (2001), Architecture for the
               automatically switched optical network (ASON).

   [M.3100]    ITU-T M.3100 (1995), Generic Network Information Model.

   [T.50]      ITU-T T.50 (1992), International Reference Alphabet.

7.  Acknowledgements

   The authors would like to thank Astrid Lozano, John Drake, Adrian
   Farrel and Stephen Shew for their valuable comments.

   The authors would like to thank ITU-T Study Group 15 Question 14 for
   their careful review and comments.

Authors' Addresses

   Don Fedyk
   Nortel Networks
   600 Technology Park Drive
   Billerica, MA, 01821

   Phone: +1 978 288-3041
   EMail: dwfedyk@nortel.com

   Osama Aboul-Magd
   Nortel Networks
   P.O. Box 3511, Station 'C'
   Ottawa, Ontario, Canada

   Phone: +1 613 763-5827
   EMail: osama@nortel.com

   Deborah Brungard
   Rm. D1-3C22
   200 S. Laurel Ave.
   Middletown, NJ 07748, USA

   EMail: dbrungard@att.com

   Jonathan P. Lang
   Sonos, Inc.
   223 E. De La Guerra
   Santa Barbara, CA 93101

   EMail: jplang@ieee.org

   Dimitri Papadimitriou
   Francis Wellesplein, 1
   B-2018 Antwerpen, Belgium

   Phone: +32 3 240-84-91
   EMail: dimitri.papadimitriou@alcatel.be

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