MPLS Working Group                                              M. Bocci
Internet-Draft                                            Alcatel-Lucent
Intended status: Standards Track                              G. Swallow
Expires: January 13, April 28, 2011                                            Cisco
                                                           July 12,
                                                                 E. Gray
                                                        October 25, 2010

                          MPLS-TP Identifiers


   This document specifies identifiers for MPLS-TP objects.  Included
   are identifiers conformant to existing ITU conventions and
   identifiers which are compatible with existing IP, MPLS, GMPLS, and
   Pseudowire definitions.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
     1.3.  Notational Conventions in Backus-Naur Form . . . . . . . .  4
   2.  Named Entities . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Uniquely Identifying an Operator . . . . . . . . . . . . . . .  5
     3.1.  The Global ID  . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  ITU Carrier Code . . . . . . . . . . . . . . . . . . . . .  5  6
   4.  Node and Interface Identifiers . . . . . . . . . . . . . . . .  6
   5.  MPLS-TP Tunnel and LSP Identifiers . . . . . . . . . . . . . .  7
     5.1.  MPLS-TP Point to Point Tunnel Identifiers  . . . . . . . .  7  8
     5.2.  MPLS-TP LSP Identifiers  . . . . . . . . . . . . . . . . .  8
     5.3.  Mapping to GMPLS Signalling  . . . . . . . . . . . . . . .  8  9
   6.  Pseudowire Path Identifiers  . . . . . . . . . . . . . . . . .  9
   7.  Maintenance Identifiers  . . . . . . . . . . . . . . . . . . .  9 10
     7.1.  Maintenance Entity Group Identifiers . . . . . . . . . . . 10
       7.1.1.  ICC based MEG_IDs  . . . .  ICC-based MEG Identifiers  . . . . . . . . . . . . . . 10
       7.1.2.  IP Compatible MEG_IDs  . . . . . . . . . . . . . . . . 10 11  MPLS-TP LSP MEG_IDs  . . . . . . . . . . . . . . . 10 11  Pseudowire MEG_IDs . . . . . . . . . . . . . . . . 10 11
     7.2.  MEP_IDs  . . . . . . . . . . . . . . . . . . . . . . . . . 11
       7.2.1.  ICC based MEP_IDs  . . . .  ICC-based MEP Identifiers  . . . . . . . . . . . . . . 11
       7.2.2.  IP based MEP_IDs . . . . . . . . . . . . . . . . . . . 11 12  MPLS-TP LSP_MEP_ID . . . . . . . . . . . . . . . . 11 12  MEP_IDs for Pseudowires  . . . . . . . . . . . . . 11 12  Endpoint IDs for Pseudowire Segments . . . . . . . 12
     7.3.  MIP_IDs  . . . . 12
     7.3.  MIP Identifiers  . . . . . . . . . . . . . . . . . . . . . 12 13
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13 14
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 14
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 13 14
     10.2. Informative References . . . . . . . . . . . . . . . . . . 14 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 15

1.  Introduction

   This document specifies identifiers to be used in within the
   Transport Profile of Multiprotocol Label Switching (MPLS-TP).  The
   MPLS-TP requirements (RFC 5654) [12] require that the elements and
   objects in an MPLS-TP environment are able to be configured and
   managed without a control plane.  In such an environment many
   conventions for defining identifiers are possible.  This document
   defines identifiers for MPLS-TP management and OAM functions suitable
   to ITU conventions and to IP/MPLS conventions.  Applicability of the
   different identifier schemas to different applications are outside
   the scope of this document.

1.1.  Terminology

   AII: Attachment Interface Identifier

   AP: Attachment Point

   ASN: Autonomous System Number

   FEC: Forwarding Equivalence Class

   GMPLS: Generalized Multi-Protocol Label Switching

   ICC: ITU Carrier Code

   LSP: Label Switched Path

   LSR: Label Switching Router

   ME: Maintenance Entity

   MEG: Maintenance Entity Group

   MEP: Maintenance Entity Group End Point

   MIP: Maintenance Entity Group Intermediate Point

   MPLS: Multi-Protocol Label Switching

   OAM: Operations, Administration and Maintenance

   P2MP: Point to Multi-Point

   P2P: Point to Point

   PW: Pseudowire
   RSVP: Resource Reservation Protocol

   RSVP-TE: RSVP Traffic Engineering

   S-PE: Switching Provider Edge

   T-PE: Terminating Provider Edge

1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [1].

1.3.  Notational Conventions in Backus-Naur Form

   All multiple-word atomic identifiers use underscores (_) between the
   words to join the words.  Many of the identifiers are composed of a
   concatenation of other identifiers, these identifiers.  These are expressed using Backus-
   Naur Form.
   Backus-Naur Form (using double-colon - "::" - notation).

   Where the same identifier type is used multiple times in a
   concatenation, they are qualified by a prefix joining it joined to the
   identifier by a dash (-).  For example Src-Node_ID is the Node_ID of
   a node referred to as Src (short (where "Src" is short for source). "source" in this

   The notation does not define an implicit ordering of the information
   elements involved in a concatenated identifier.

2.  Named Entities

   In order to configure, operate and manage a transport network based
   on the MPLS Transport Profile, a number of entities require
   identification.  Identifiers for the follow entities are defined in
   this document:

   o  Operator

      *  Global_ID

      *  ICC

   o  LSR

   o  LSP
   o  PW

   o  Interface

   o  MEG

   o  MEP

   o  MIP

   o  Tunnel

   Note that we have borrowed the term tunnel from RSVP-TE (RFC 3209)
   [2] where it is used to describe an entity that provides a connection
   between a source and destination LSR.  The tunnel in turn is
   instantiated by one or more LSPs, where the additional LSPs are used
   for protection or re-grooming of the tunnel.

3.  Uniquely Identifying an Operator

   Two forms of identification are defined, one that is compatible with
   IP operational practice called a Global_ID and one compatible with
   ITU practice, the ICC.  An Operator MAY be identified either by its
   Global_ID or by its ICC.

3.1.  The Global ID

   RFC 5003 [3] defines a globally unique Attachment Interface
   Identifier (AII).  That AII is composed of three parts, a Global_ID
   which uniquely identifies a operator, a prefix, and finally and
   attachment circuit identifier.  We have chosen to use that Global ID
   for MPLS-TP.  Quoting from RFC 5003, section 3.2, "The global ID can
   contain the 2-octet or 4-octet value of the operator's Autonomous
   System Number (ASN).  It is expected that the global ID will be
   derived from the globally unique ASN of the autonomous system hosting
   the PEs containing the actual AIIs.  The presence of a global ID
   based on the operator's ASN ensures that the AII will be globally

   When the Global_ID is derived from a 2-octet AS number, the two high-
   order octets of this 4-octet identifier MUST be set to zero.

   Note that this Global_ID is used solely to provide a globally unique
   context for other MPLS-TP identifiers.  It has nothing to do with the
   use of the ASN in protocols such as BGP.

3.2.  ITU Carrier Code

   M.1400 defines the ITU Carrier Code (ICC) assigned to a network
   operator/service provider and maintained by the ITU-T
   Telecommunication Standardization Bureau (TSB):

   ICCs can be assigned both to ITU-T and non-ITU-T members and the
   referenced local ICC website may contain ICCs of operators of both

   The ICC is a string of one to six characters, each character being
   either alphabetic (i.e.  A-Z) or numeric (i.e. 0-9) characters.
   Alphabetic characters in the ICC SHOULD be represented with upper
   case letters.

4.  Node and Interface Identifiers

   An LSR requires identification of the node itself and of its
   interfaces.  An interface is the Access Point (AP) to a server layer
   MPLS-TP section or MPLS-TP tunnel.

   We call the identifier associated with a node a Node Identifier
   (Node_ID).  The Node_ID is a unique 32-bit unsigned integer value assigned by the
   operator within the scope of the Global_ID.  The value 0 (or in dotted decimal notation) zero is
   reserved and MUST NOT be used.
   The Node_ID is not an IPv4 address.  However, it was chosen to be 32-
   bits to allow compatibility with existing MPLS deployments.  In
   existing MPLS deployments LSRs are generally identified by an IPv4
   loopback address.  Where IPv4 addresses are in use the Node_ID MAY be
   automatically mapped used, it is
   convenient to use the LSR's /32 Node's IPv4 loopback address.  Note
   that, when IP reachability is not needed, address as the Node_ID,
   however the 32-bit Node_ID is does not
   required need to have any association with the
   IPv4 address space used in the operator's IGP or BGP.  Where IPv6
   addresses are used exclusively, a domain unique 32- bit value is

   In situations where a Node_ID needs to be globally unique, this is
   accomplished by prefixing the identifier with the operator's
   Global_ID.  The combination of Global_ID::Node_ID we call an Global
   Node ID or Global_Node_ID.

   Within the context of a particular node, we call the identifier
   associated with an interface an Interface Number or IF_Num. The
   IF_Num is a 32-bit unsigned integer assigned by the operator and MUST
   be unique within the scope of a Node_ID.  The IF_Num value 0 has
   special meaning (see section Section 7.3 and must not MUST NOT be used as the IF_Num in an MPLS-TP

   An Interface Identifier or IF_ID identifies an interface uniquely
   within the context of a Global_ID.  It is formed by concatenating the
   Node_ID with the IF_Num. That is an IF_ID is a 64-bit identifier
   formed as Node_ID::IF_Num.

   This convention was chosen to allow compatibility with GMPLS.  GMPLS
   signaling [4] requires interface identification.  GMPLS allows three
   formats for the Interface_ID.  The third format consists of an IPv4
   Address plus a 32-bit unsigned integer for the specific interface.
   The format defined for MPLS-TP is consistent with this format, but
   uses the Node_ID instead of an IPv4 Address.

   An IF_ID needs to be globally unique, this is accomplished by
   prefixing the identifier with the operator's Global_ID.  The
   combination of Global_ID::Node_ID::IF_Num we call an Global Interface
   ID or Global_IF_ID.

   The attachment point to an MPLS-TP Tunnel (see section Section 5.1
   also needs an interface identifier.  A procedure for automatically
   generating these is contained in that section.

5.  MPLS-TP Tunnel and LSP Identifiers


   An important construct within MPLS_TP is a connection which is service that may be
   identified by the server to a client, ideally using a single
   identifier.  Such a service may be provided across a working and a
   protection LSP. LSP, both of which should be similarly identified.  Within
   this document we will use the term MPLS-TP Tunnel "MPLS-TP Tunnel" or simply tunnel
   "tunnel" for the
   connection a service provided by the (for example) a working and protect
   protection LSPs.  This section defines an MPLS-TP Tunnel_ID to
   uniquely identify a tunnel and MPLS-TP LSP_IDs within the context of a
   that tunnel.

   For the case where multiple LSPs (for example) are used to support a
   single service with a common set of end-points, using this identifier
   allows for a trivial mapping between the server and client layers to
   a common service identifier which may be either defined by, or used
   by, the client.

   Note that this usage is not intended to constrain protection schemes,
   and may be used to identify any service (protected or un-protected)
   that may appear to the client as a single service attachment point.
   Keeping the tunnel number consistent across working and protection
   LSPs is a useful construct currently employed within GMPLS.  However
   there is no requirement that a protection LSP use the same tunnel
   number as the working LSP.

5.1.  MPLS-TP Point to Point Tunnel Identifiers

   At each endpoint a tunnel is uniquely identified by the endpoint's
   Node_ID and a locally assigned tunnel number.  Specifically a
   Tunnel_Num is a 16-bit unsigned integer unique within the context of
   the node.  The motivation for each endpoint having its own tunnel
   number is to allow a compact form for the MEP-ID.  See section

   Having two tunnel-ids also serves to simplify other signaling.  For
   instance an associated bi-directional tunnel could be setup using two
   unidirectional tunnels signaled via RSVP.

   The concatenation of the two endpoint identifier servers identifiers serves as the full
   identifier.  In a signaled situation, the node originating the
   signaling exchange is called the source and the target node is called
   the destination.  In a configured environment the endpoints could
   equally be called East and West.  Using the signaled convention and
   abbreviating the endpoint qualifiers to Src and Dst respectively, the
   format of the format of a Tunnel_ID is:


   Where the Tunnel_ID needs to be globally unique, this is accomplished
   by using globally unique Node_IDs as defined above.  Thus a globally
   unique Tunnel_ID becomes:


   When an MPLS-TP Tunnel is configured, it MUST be assigned a unique
   IF_ID at both the source and destination endpoints.  As usual, the
   IF_ID is composed of the local NODE_ID concatenated with a 32-bit
   IF_Num. It is RECOMMENDED that the IF_Num be auto-generated by adding
   2^31 to the local Tunnel_Num.

5.2.  MPLS-TP LSP Identifiers

   Within the scope of an MPLS-TP Tunnel_ID an LSP can be uniquely
   identified by a single LSP number.  Specifically an LSP_Num is a 16-
   bit unsigned integer unique within the Tunnel_ID.  Thus the format of
   a LSP_ID is:


   Where the LSP_ID needs to be globally unique, this is accomplished by
   using globally unique Node_IDs as defined above.  Thus a globally
   unique Tunnel_ID becomes:


   The corresponding ICC-based version of this identifier would be:


5.3.  Mapping to GMPLS Signalling

   This section defines the mapping from an MPLS-TP LSP_ID to GMPLS.  At
   this time, GMPLS has yet to be extended to accommodate Global_IDs.
   Thus a mapping is only made for the network unique form of the

   GMPLS signaling [5] uses a 5-tuple to uniquely identify an LSP within
   a operator's network.  This tuple is composed of a Tunnel Endpoint
   Address, Tunnel_ID, Extended Tunnel ID, and Tunnel Sender Address and

   In situations where a mapping to the GMPLS 5-tuple is required, the
   following mapping is used.

   o  Tunnel Endpoint Address = Dst-Node_ID

   o  Tunnel_ID = Src-Tunnel_Num

   o  Extended Tunnel_ID = Src-Node_ID

   o  Tunnel Sender Address = Src-Node_ID

   o  LSP_ID = LSP_Num

6.  Pseudowire Path Identifiers

   Pseudowire signaling (RFC 4447 [6]) defines two FECs used to signal
   pseudowires.  Of these, FEC Type 129 along with AII Type 2 as defined
   in RFC 5003 [3] fits the identification requirements of MPLS-TP.

   In an MPLS-TP environment, a PW is identified by a set of identifiers
   which can be mapped directly to the elements required by FEC 129 and
   AII Type 2.  To distinguish this identifier from other Pseudowire
   Identifiers, we call this a Pseudowire Path Identifier or PW_Path_Id.

   The AII Type 2 is composed of three fields.  These are the Global_ID,
   the Prefix, and the AC_ID.  The Global_ID used in this document is
   identical to the Global_ID defined in RFC 5003.  The Node_ID is used
   as the Prefix.  The AC_ID is as defined in RFC 5003.

   To complete the FEC 129, all that is required is a Attachment Group
   Identifier (AGI).  That field is exactly as specified in RFC 4447.
   FEC 129 has a notion of Source AII (SAII) and Target AII (TAII).
   These terms are used relative to the direction of the signaling.  In
   a purely configured environment when referring to the entire PW, this
   distinction is not critical.  That is a FEC 129 of AGIa::AIIb::AIIc
   is equivalent to AGIa::AIIc::AIIb.  We note that in a signaled
   environment, the required convention in RFC 4447 is that at a
   particular endpoint, the AII associated with that endpoint comes
   first.  The complete PW_Path_Id is:



   The corresponding ICC-based version for this identifier would be:


7.  Maintenance Identifiers

   In MPLS-TP a Maintenance Entity Group (MEG) represents an Entity that
   requires management and defines a relationship between a set of
   maintenance points.  A maintenance point is either Maintenance Entity
   Group End-point (MEP) or a Maintenance Entity Group Intermediate
   Point (MIP).  Maintenance points are uniquely associated with a MEG.
   Within the context of a MEG, MEPs and MIPs must be uniquely
   identified.  This section defines a means of uniquely identifying
   Maintenance Entity Groups, Maintenance Entities and uniquely defining
   MEPs and MIPs within the context of a Maintenance Entity Group.

   Note that depending on the requirements of a particular OAM
   interaction, the MPLS-TP maintenance entity context may be provided
   either explicitly using the MEG_IDs described above or implicitly by
   the label of the received OAM message.

7.1.  Maintenance Entity Group Identifiers

   Maintenance Entity Group Identifiers (MEG_IDs) are required for
   MPLS-TP LSPs and Pseudowires.  Two classes of MEG_IDs are defined,
   one that follows the IP compatible identifier defined above as well
   as the ICC-format.

7.1.1.  ICC based MEG_IDs  ICC-based MEG Identifiers

   MEG_ID for MPLS-TP LSPs and Pseudowires MAY use the globally unique
   ICC-based format.

   In this case, the MEG_ID is a string of up to thirteen characters,
   each character being either alphabetic (i.e.  A-Z) or numeric (i.e.
   0-9) characters.  It consists of two subfields: the ICC (as defined
   in section 3) followed by a unique MEG code (UMC).  The UMC MUST be
   unique within the organization identified by the ICC.

   The ICC MEG_ID may be applied equally to a single MPLS-TP LSP or
   Pseudowires.  Note that when encoded in a protocol such as in a TLV,
   a different type needs to be defined for LSP and PWs as the OAM
   capabilities may be different.

7.1.2.  IP Compatible MEG_IDs  MPLS-TP LSP MEG_IDs

   Since a MEG pertains to a single MPLS-TP LSP, IP compatible MEG_IDs
   for MPLS-TP LSPs are simply the corresponding LSP_IDs.  We note that
   while the two identifiers are syntactically identical, they have
   different semantics.  This semantic difference needs to be made
   clear.  For instance if both a MPLS-TP LSP_ID and MPLS-TP LSP MEG_IDs
   are to be encoded in TLVs different types need to be assigned for
   these two identifiers.  Pseudowire MEG_IDs

   For Pseudowires a MEG pertains to a single PW.  The IP compatible
   MEG_ID for a PW is simply the corresponding PW_Path_ID.  We note that
   while the two identifiers are syntactically identical, they have
   different semantics.  This semantic difference needs to be made
   clear.  For instance if both a PW_Path_ID and a PW_MEG_ID is to be
   encoded in TLVs different types need to be assigned for these two

7.2.  MEP_IDs

7.2.1.  ICC based MEP_IDs  ICC-based MEP Identifiers

   ICC-based MEP_IDs for MPLS-TP LSPs and Pseudowires are formed by
   appending a unique number to the MEG_ID defined in section
   Section 7.1.1 above.  Within the context of a particular MEG, we call
   the identifier associated with a MEP the MEP Index (MEP_Index).  The
   MEP_Index is administratively assigned.  It is encoded as a 16-bit
   unsigned integer and MUST be unique within the MEG.  An ICC-based
   MEP_ID is:


   An ICC-based MEP ID is globally unique by construction given the ICC-
   based MEG_ID global uniqueness.

7.2.2.  IP based MEP_IDs  MPLS-TP LSP_MEP_ID

   In order to automatically generate MEP_IDs for MPLS-TP LSPs, we use
   the elements of identification that are unique to an endpoint.  This
   ensures that MEP_IDs are unique for all LSPs within a operator.  When
   Tunnels or LSPs cross operator boundaries, these are made unique by
   pre-pending them with the operator's Global_ID.



   where the Node_ID is the node in which the MEP is located and
   Tunnel_Num is the tunnel number unique to that node.

   In situations where global uniqueness is required this becomes:

      Src-Global_ID::Src-Node_ID::Src-Tunnel_Num::LSP_Num  MEP_IDs for Pseudowires

   Like MPLS-TP LSPs, Pseudowire endpoints (T-PEs) require MEP_IDs.  In
   order to automatically generate MEP_IDs for PWs, we simply use the
   AGI plus the AII associated with that end of the PW.  Thus a MEP_ID
   used in end-to-end for an Pseudowire T-PE takes the form


   where the Node_ID is the node in which the MEP is located and
   Tunnel_Num is the tunnel number unique to that node.  Endpoint IDs for Pseudowire Segments

   In some OAM communications, messages are originated by the node at
   one end of a PW segment and relayed to the other end of that same
   segment by setting the TTL of the PW label to one. one (1).  For a multi-
   segment pseudowire, TTL could be set to any value that would cause
   OAM messages to reach the target segment end-point (up to and
   including 255).

   The MEP_ID Is Formed by a combination of a PW MEP_ID and the
   identification of the local node.  At an S-PE, there are two PW
   segments.  We distinguish the segments by using the MEP_ID which is
   upstream of the PW segment in question.  To complete the
   identification we suffix this with the identification of the local

      +-------+         +-------+         +-------+         +-------+
      |       |         |       |         |       |         |       |
      |      A|---------|B     C|---------|D     E|---------|F      |
      |       |         |       |         |       |         |       |
      +-------+         +-------+         +-------+         +-------+
        T-PE1             S-PE2             S-PE3             T-PE4
       (T)PE1            (S)PE2            (S)PE3            (T)PE4

                       Pseudowire Maintenance Points

   For example, suppose that in the above figure all of the nodes have
   Global_ID GID1; the node are represented as named in the figure; and
   The identification for the Pseudowire is:

           AGI           = AGI1
           Src-Global_ID = GID1
           Src-Node_ID   = T-PE1 PE1
           Src-AC_ID     = AII1
           Dst-Global_ID = GID1
           Dst-Node_ID   = T-PE1 PE4
           Dst-AC_ID     = AII4

   The PW segment endpoint MEP_ID at point A would be AGI1::GID1:T-PE1::AII1. -


   The MP_ID at point C would be AGI1::GID1:T-PE1::AII1::GID1:S-PE2. -


7.3.  MIP_IDs  MIP Identifiers

   At a cross connect cross-connect point, in order to automatically generate MIP_IDs
   for MPLS-TP, we simply use the IF_IDs of the two interfaces which are
   cross connected
   cross-connected via the label bindings of the MPLS-TP LSP.  If only
   one MIP is configured, then the MIP_ID is formed using the Node_ID
   and an IF_Num of 0.  In some contexts, such as LSP Ping[13], the
   Node_ID alone may be used as the MIP_ID.

8.  IANA Considerations

   There are no IANA actions resulting from this document.

9.  Security Considerations

   This document describes an information model and, as such, does not
   introduce security concerns.  Protocol specifications that describe
   use of this information model - however - may introduce security
   risks and concerns about authentication of participants.  For this
   reason, the writers of protocol specifications for the purpose of
   describing implementation of this information model need to describe
   security and authentication concerns that may be raised by the
   particular mechanisms defined and how those concerns may be

10.  References

10.1.  Normative References

   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [2]   Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and
         G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels",
         RFC 3209, December 2001.

   [3]   Metz, C., Martini, L., Balus, F., and J. Sugimoto, "Attachment
         Individual Identifier (AII) Types for Aggregation", RFC 5003,
         September 2007.

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

   [5]   Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS)
         Signaling Resource ReserVation Protocol-Traffic Engineering
         (RSVP-TE) Extensions", RFC 3473, January 2003.

   [6]   Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron,
         "Pseudowire Setup and Maintenance Using the Label Distribution
         Protocol (LDP)", RFC 4447, April 2006.

   [7]   Kompella, K., Rekhter, Y., and A. Kullberg, "Signalling
         Unnumbered Links in CR-LDP (Constraint-Routing Label
         Distribution Protocol)", RFC 3480, February 2003.

   [8]   Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling in
         MPLS Traffic Engineering (TE)", RFC 4201, October 2005.

   [9]   Lang, J., Rekhter, Y., and D. Papadimitriou, "RSVP-TE
         Extensions in Support of End-to-End Generalized Multi-Protocol
         Label Switching (GMPLS) Recovery", RFC 4872, May 2007.

   [10]  Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "BFD
         "Bidirectional Forwarding Detection (BFD) for MPLS LSPs", draft-ietf-bfd-mpls-07 (work in progress), Label
         Switched Paths (LSPs)", RFC 5884, June 2008. 2010.

   [11]  Nadeau, T. and C. Pignataro, "Bidirectional Forwarding
         Detection (BFD) for the Pseudowire Virtual Circuit Connectivity
         Verification (VCCV)", draft-ietf-pwe3-vccv-bfd-07 (work in
         progress), July 2009. RFC 5885, June 2010.

10.2.  Informative References

   [12]  Vigoureux, M.  Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and D. Ward,
         S. Ueno, "Requirements for OAM in of an MPLS Transport Networks", draft-ietf-mpls-tp-oam-requirements-06
         (work in progress), March 2010. Profile", RFC 5654,
         September 2009.

   [13]  Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label
         Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.

   [14]  Ohta, H., "Assignment of the 'OAM Alert Label' for
         Multiprotocol Label Switching Architecture (MPLS) Operation and
         Maintenance (OAM) Functions", RFC 3429, November 2002.

   [15]  Niven-Jenkins, B., Brungard,  Vigoureux, M., Ward, D., and M. Betts, M., Sprecher, N., "Requirements for
         Operations, Administration, and
         S. Ueno, "MPLS-TP Requirements",
         draft-ietf-mpls-tp-requirements-10 (work Maintenance (OAM) in progress),
         August 2009. MPLS
         Transport Networks", RFC 5860, May 2010.

   [16]  Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, "A
         Framework for MPLS in Transport Networks",
         draft-ietf-mpls-tp-framework-12 (work in progress), May RFC 5921, July 2010.

Authors' Addresses

   Matthew Bocci
   Voyager Place, Shoppenhangers Road
   Maidenhead, Berks  SL6 2PJ


   George Swallow

   Eric Gray
   900 Chelmsford Street
   Lowell, Massachussetts  01851-8100