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Versions: (draft-swallow-mpls-tp-identifiers) 00 01 02 03 04 05 06 07 RFC 6370

MPLS Working Group                                              M. Bocci
Internet-Draft                                            Alcatel-Lucent
Intended status: Standards Track                              G. Swallow
Expires: May 14, 2010                                              Cisco
                                                       November 10, 2009


                          MPLS-TP Identifiers
                   draft-ietf-mpls-tp-identifiers-00

Abstract

   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.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on May 14, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Named Entities . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Uniquely Identifying an Operator . . . . . . . . . . . . . . .  5
     3.1.  The Global ID  . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  ITU Carrier Code . . . . . . . . . . . . . . . . . . . . .  5
   4.  Node and Interface Identifiers . . . . . . . . . . . . . . . .  6
   5.  MPLS-TP Tunnel and LSP Identifiers . . . . . . . . . . . . . .  7
     5.1.  MPLS-TP Tunnel Identifiers . . . . . . . . . . . . . . . .  7
     5.2.  MPLS-TP LSP Identifiers  . . . . . . . . . . . . . . . . .  7
     5.3.  Mapping to GMPLS Signalling  . . . . . . . . . . . . . . .  8
   6.  Pseudowire Path Identifiers  . . . . . . . . . . . . . . . . .  8
   7.  Maintenance Identifiers  . . . . . . . . . . . . . . . . . . .  9
     7.1.  Maintenance Entity Group Identifiers . . . . . . . . . . .  9
       7.1.1.  ICC based MEG_IDs  . . . . . . . . . . . . . . . . . .  9
       7.1.2.  IP Compatible MEG_IDs  . . . . . . . . . . . . . . . . 10
         7.1.2.1.  MPLS-TP Tunnel MEG_IDs . . . . . . . . . . . . . . 10
         7.1.2.2.  MPLS-TP LSP MEG_IDs  . . . . . . . . . . . . . . . 10
         7.1.2.3.  Pseudowire MEG_IDs . . . . . . . . . . . . . . . . 10
     7.2.  Maintenance Points . . . . . . . . . . . . . . . . . . . . 11
       7.2.1.  Maintenance Point_IDs for MPLS-TP LSPs and Tunnels . . 11
         7.2.1.1.  MPLS-TP Tunnel_MEP_ID  . . . . . . . . . . . . . . 11
         7.2.1.2.  MPLS-TP LSP_MEP_ID . . . . . . . . . . . . . . . . 11
         7.2.1.3.  MPLS-TP LSP_MIP_ID . . . . . . . . . . . . . . . . 11
       7.2.2.  Maintenance Identifiers for Pseudowires  . . . . . . . 12
         7.2.2.1.  MEP_IDs for PW T-PEs . . . . . . . . . . . . . . . 12
         7.2.2.2.  MP_IDs for Pseudowires . . . . . . . . . . . . . . 12
   8.  Open issues  . . . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 13
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15









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1.  Introduction

   This document specifies identifiers to be used in within the
   Transport Profile of Multiprotocol Label Switching (MPLS-TP). where
   compatibility with existing MPLS control plane conventions are
   necessary.  The MPLS-TP requirements [13] 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.  In particular,
   identifiers conformant to existing ITU conventions are defined.  It
   is also anticipated that operational environments where MPLS-TP
   objects, e.g.  Label Switched Paths (LSPs) and Pseudowires (PWs) will
   be signaled via existing protocols such as the Label Distribution
   Protocol (RFC 4447) [1] and the Resource Reservation Protocol as it
   is applied to Generalized Multi-protocol Label Switching (RFCs 3471 &
   3473) [2][3] (GMPLS).  This document defines a set of identifiers for
   MPLS-TP which are both compatible with those protocols and applicable
   to MPLS-TP management and OAM functions.

1.1.  Terminology

   AII: Attachment Interface Identifier

   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 End Point

   MIP: Maintenance Intermediate Point

   MPLS: Multi-Protocol Label Switching

   OAM: Operations, Administration and Maintenance

   P2MP: Point to Multi-Point



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   P2P: Point to Point

   PSC: Protection State Coordination

   PW: Pseudowire

   RSVP: Resource Reservation Protocol

   RSVP-TE: RSVP Traffic Engineering

   S-PE: Switching Provider Edge

   T-PE: Terminating Provider Edge

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [4].


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

      *  ICC

      *  Global_ID

   o  LSR

   o  LSP

   o  PW

   o  Interface

   o  MEG

   o  MEP

   o  MIP




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   o  Tunnel

   Note that we have borrowed the term tunnel from RSVP-TE (RFC 3209)
   [5] where it is used to describe an entity that provides an LSP
   connection between a source and destination LSR which 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 [6] 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
   unique."

   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): www.itu.int/ITU-T/
   inr/icc/index.html.

   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
   kinds.




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   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.  We call the identifier associated with a node a Node
   Identifier (Node_ID).  Within the context of a particular node, we
   call the identifier associated with an interface an Logical Interface
   Handle or LIH.  The combination of Node_ID::LIH we call an Network
   Interface ID or IF_ID.

   In existing MPLS deployments Node_IDs are IPv4 addresses.  Therefore
   we have chosen the Node_ID to be a 32-bit value assigned by the
   operator.  Where IPv4 addresses are in use the Node_ID can be
   automatically mapped to the LSR's /32 IPv4 loopback address.  Note
   that, when IP reachability is not needed, the 32-bit Node_ID is not
   required to have any association with the IPv4 address space used in
   the operator's IGP or BGP, other that that they be uniquely chosen
   within the scope of that operator.

   GMPLS signaling [2] requires interface identification.  We have
   chosen to adopt the conventions of that RFC.  GMPLS allows three
   formats for the Interface_ID.  For IP numbered links, it is simply
   the IPv4 or IPv6 address associated with the interface.  The third
   format consists of an IPv4 Address plus a 32-bit unsigned integer for
   the specific interface.

   For MPLS-TP, we have adopted a format consistent with the third
   format above.  In MPLS-TP, each interface is assigned a 32-bit
   identifier which we call a Logical Interface Handle (LIH).  The LIH
   MUST be unique within the context of the Node_ID.  We map the Node_ID
   to the field the field which carries the IP address.  That is, an
   IF_ID is a 64-bit identifier consisting of the Node_ID followed by
   the LIH.  The LIH in turn is a 32-bit unsigned integer unique to the
   node.  The LIH value 0 has special meaning (see section
   Section 7.2.1.3 and must not be used as the LIH in an MPLS-TP IF_ID.

   In situations where a Node_ID or 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 we call
   an Global Node ID or Global_Node_ID.  Likewise, the combination of
   Global_ID::Node_ID::LIH we call an Global Interface ID or
   Global_IF_ID.




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   MPLS-TP Tunnels (see section Section 5.1) also need interface
   identifiers.  A procedure for automatically generating these is
   contained in that section.


5.  MPLS-TP Tunnel and LSP Identifiers

   A important construct within MPLS_TP is a connection which is
   provided across a working and a protection LSP.  Within this document
   we will use the term MPLS-TP Tunnel or simply tunnel for the
   connection provided by the working and protect LSPs.  This section
   defines an MPLS-TP Tunnel_ID to uniquely identify a tunnel and
   MPLS-TP LSP_IDs within the context of a tunnel.

5.1.  MPLS-TP Tunnel Identifiers

   At each endpoint a tunnel is uniquely identified by the Source
   Node_ID and a locally assigned tunnel number.  Specifically a
   Tunnel_Num is a 16-bit unsigned integer unique to the node.  The
   concatenation of the two endpoint identifier servers as the full
   identifier.  Thus the format of a Tunnel_ID is:

      Src-Node_ID::Src-Tunnel_Num::Dst-Node_ID::Dst-Tunnel_Num

   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:

      Src-Global_ID::Src-Node_ID::Src-Tunnel_Num:: Dst-Global_ID::Dst-
      Node_ID::Dst-Tunnel_Num

   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
   LIH.  It is RECOMMENDED that the LIH 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 Tunnel_ID is:

      Src-Node_ID::Src-Tunnel_Num::Dst-Node_ID::Dst-Tunnel_Num:: LSP_Num

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



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   unique Tunnel_ID becomes:

      Src-Global_ID::Src-Node_ID::Src-Tunnel_Num:: Dst-Global_ID::Dst-
      Node_ID::Dst-Tunnel_Num::LSP_Num

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
   LSP_ID.

   GMPLS signaling [3] 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
   (GMPLS) LSP_ID.

   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 [1]) defines two FECs used to signal
   pseudowires.  Of these, FEC Type 129 along with AII Type 2 as defined
   in RFC 5003 [6] 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



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   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:

      AGI:Src-Global_ID::Src-Node_ID::Src-AC_ID:: Dst-Global_ID::Dst-
      Node_ID::Dst-AC_ID.


7.  Maintenance Identifiers

   [Note this section needs to reconciled with on going ITU and MPLS WG
   discussions on Maintenance Points.]

   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 End-
   point (MEP) or a Maintenance Intermediate Point (MIP).  A Maintenance
   Entity is a relationship between two MEPs.  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.

7.1.  Maintenance Entity Group Identifiers

   Maintenance Entity Group Identifiers (MEG_IDs) are required for
   MPLS-TP Paths 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

   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 MPLS-TP tunnels, a single



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   MPLS-TP LSP, groups of MPLS-TP LSPs, Pseudowires, and groups of
   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

7.1.2.1.  MPLS-TP Tunnel MEG_IDs

   Since a MEG pertains to a single MPLS-TP Tunnel, IP compatible
   MEG_IDs for MPLS-TP Tunnels are simply the corresponding Tunnel_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 Tunnel_ID and MPLS-TP
   Tunnel MEG_IDs are to be encoded in TLVs different types need to be
   assigned for these two identifiers.

7.1.2.2.  MPLS-TP LSP MEG_IDs

   MEG_IDs for MPLS-TP LSPs may pertain to one or more LSPs.  Therefore
   the direct mapping used for tunnels is not possible.  However an
   indirect mapping which keeps the formats aligned is possible.  This
   is done by replacing the LSP_Num with a LSP_MEG_Num. Thus the format
   of a MPLS-TP LSP MEG_ID is:

      Src-Global_ID::Src-Node_ID::Src-Tunnel_Num:: Dst-Global_ID::Dst-
      Node_ID::Dst-Tunnel_Num::LSP_MEG_Num

   When a MEG_ID is assigned to a single MPLS-TP LSP it is RECOMMENDED
   that the LSP_MEG_Num be assigned equal to the LSP_Num. When a MEG_ID
   is assigned to a group of MPLS-TP LSPs within a single MPLS-TP
   Tunnel, it is recommended that the MEG_ID be assigned equal to the
   LSP_Num of one member of the group of MPLS-TP LSPs.  In this
   situation if the chosen LSP is later deconfigured it is RECOMMENDED
   that this LSP_Num not be reused unless the new LSP in question will
   become a member of the same MEG.

7.1.2.3.  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
   identifiers.



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7.2.  Maintenance Points

   Maintenance points are uniquely associated with a MEG.  Within the
   context of a MEG, MEPs and MIPs must be uniquely identified.  This
   section describes how MIPs and MEPs are identified.

   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.

7.2.1.  Maintenance Point_IDs for MPLS-TP LSPs and Tunnels

   In order to automatically generate MEP_IDs for MPLS-TP Tunnels and
   LSPs, we use the elements of identification that are unique to an
   endpoint.  This ensures that MEP_IDs are unique for all Tunnels and
   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.

7.2.1.1.  MPLS-TP Tunnel_MEP_ID

   A MPLS-TP Tunnel_MEP_ID is:

      Src-Node_ID::Src-Tunnel_Num

   In situations where global uniqueness is required this becomes:

      Src-Global_ID::Src-Node_ID::Src-Tunnel_Num

7.2.1.2.  MPLS-TP LSP_MEP_ID

   A MPLS-TP LSP_MEP_ID is:

      Src-Node_ID::Src-Tunnel_Num::LSP_Num

   In situations where global uniqueness is required this becomes:

      Src-Global_ID::Src-Node_ID::Src-Tunnel_Num::LSP_Num

7.2.1.3.  MPLS-TP LSP_MIP_ID

   At a cross connect point, in order to automatically generate MIP_IDs
   for MPLS-TP LSPs, we simply use the IF_IDs of the two interfaces
   which are 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 LIH of 0.




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7.2.2.  Maintenance Identifiers for Pseudowires

   Like MPLS-TP LSPs, Pseudowire endpoints (T-PEs) require MEP-IDs.
   Pseudowire S-PEs, however, are a special case.  Here the Maintenance
   Entity takes on some of the functionality of both a MIP and a MEP.
   Provisionally we are calling these a Maintenance Point or MP.

7.2.2.1.  MEP_IDs for PW T-PEs

   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
   for an Pseudowire T-PE takes the form:

      AGI:Src-Global_ID::Src-Node_ID::Src-AC_ID

7.2.2.2.  MP_IDs for Pseudowires

   The MP_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
   node.


      +-------+         +-------+         +-------+         +-------+
      |       |         |       |         |       |         |       |
      |      A|---------|B     C|---------|D     E|---------|F      |
      |       |         |       |         |       |         |       |
      +-------+         +-------+         +-------+         +-------+
        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
           Src-AC_ID     = AII1
           Dst-Global_ID = GID1
           Dst-Node_ID   = T-PE1
           Dst-AC_ID     = AII4

   The MEP_ID at point A would be AGI1::GID1:T-PE1::AII1.  The MP_ID at



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

   For interaction where the T-PE is acting as the segment endpoint, it
   too may use the MP_ID.


8.  Open issues

   1.  We have two means of identifying operators.  Should either be
       allowed in all cases or can we constrain this.  I.e. when there
       are both IP compatible and ITU compatible IDs for an Object can
       we constrain the operator ID to the corresponding format?
       Clearly when only one identifier is defined the both must be
       allowed.

   2.  Details on MEP and MIP identifiers are subject to ongoing
       discussions.  Further based on some discussion in Stockholm, ITU
       style identifiers for MEPs and MIPs were removed from this
       version.  However, consensus for this needs to be verified.

   3.  Pseudowire Maintenance Points need to be kept aligned with the
       model for Pseudowire maintenance.

   4.  Identifiers for P2MP entities

   5.  Tandem connection Identification - the identification should be
       exactly the same as any other MPLS-TP LSP.  However, in the ACH
       TLV draft we could have a different TLV with the same format as
       an MPLS-TP LSP, if there are places where the distinction becomes
       important.


9.  References

9.1.  Normative References

   [1]   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.

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

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

   [4]   Bradner, S., "Key words for use in RFCs to Indicate Requirement



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         Levels", BCP 14, RFC 2119, March 1997.

   [5]   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.

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

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

   [10]  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.

   [11]  Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "BFD
         For MPLS LSPs", draft-ietf-bfd-mpls-07 (work in progress),
         June 2008.

   [12]  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.

9.2.  Informative References

   [13]  Vigoureux, M., Ward, D., and M. Betts, "Requirements for OAM in
         MPLS Transport Networks",
         draft-ietf-mpls-tp-oam-requirements-03 (work in progress),
         August 2009.

   [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, D., Betts, M., Sprecher, N., and
         S. Ueno, "MPLS-TP Requirements",
         draft-ietf-mpls-tp-requirements-10 (work in progress),
         August 2009.



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   [16]  Bocci, M., Bryant, S., Frost, D., and L. Levrau, "A Framework
         for MPLS in Transport Networks",
         draft-ietf-mpls-tp-framework-06 (work in progress),
         October 2009.


Authors' Addresses

   Matthew Bocci
   Alcatel-Lucent
   Voyager Place, Shoppenhangers Road
   Maidenhead, Berks  SL6 2PJ
   UK

   Email: matthew.bocci@alcatel-lucent.com


   George Swallow
   Cisco

   Email: swallow@cisco.com






























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