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Versions: 00 01 02 draft-ietf-mpls-tp-identifiers

MPLS Working Group                                              M. Bocci
Internet-Draft                                            Alcatel-Lucent
Intended status: Standards Track                              G. Swallow
Expires: January 14, 2010                                          Cisco
                                                           July 13, 2009


                          MPLS-TP Identifiers
                  draft-swallow-mpls-tp-identifiers-01

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

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Abstract

   This document specifies identifiers for MPLS-TP objects.  Included
   are identifiers conformant to existing ITU conventions and



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   identifiers which are compatible with existing IP, MPLS, GMPLS, and
   Pseudowire definitions.


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.  Path Identifiers . . . . . . . . . . . . . . . . . . . . . . .  6
     5.1.  MPLS-TP LSP Identifiers  . . . . . . . . . . . . . . . . .  7
     5.2.  Pseudowire Identifiers . . . . . . . . . . . . . . . . . .  8
   6.  Maintenance Identifiers  . . . . . . . . . . . . . . . . . . .  8
     6.1.  Maintenance Entity Identifiers . . . . . . . . . . . . . .  8
       6.1.1.  IP Compatible ME-IDs . . . . . . . . . . . . . . . . .  9
       6.1.2.  ICC based ME-IDs . . . . . . . . . . . . . . . . . . .  9
     6.2.  Maintenance Points . . . . . . . . . . . . . . . . . . . .  9
     6.3.  MEP_IDs for MPLS-TP LSPs and Tunnels . . . . . . . . . . .  9
     6.4.  MEP_IDs for Pseudowires  . . . . . . . . . . . . . . . . . 10
     6.5.  Maintenance Intermediate Point Identifiers . . . . . . . . 10
   7.  Open issues  . . . . . . . . . . . . . . . . . . . . . . . . . 10
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13






















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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 conformat 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: Generalised Multi-Protocol Label Switching

   ICC: ITU Carrier Code

   LSP: Label Switched Path

   LSR: Label Switching Router

   ME: Maintenance Entity

   MEP: Maintenance End Point

   MIP: Maintenance Intermediate Point

   MPLS: Multi-Protocol Label Switching

   OAM: Operations, Administration and Maintenance

   P2MP: Point to Multi-Point

   P2P: Point to Point



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   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

   o  Tunnel




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   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 containu ICCs of operators of both
   kinds.

   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.



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   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 Network_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 consitent with the third format
   above.  In MPLS-TP, each interface is assigned a 32-bit identifier
   which we call an 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, a Nework_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.

   In situations where a Node_ID or an Network_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.


5.  Path Identifiers





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5.1.  MPLS-TP LSP Identifiers

   [Note: See proposed changes to in the issues section]

   GMPLS signalling [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 LSP_ID.  For MPLS-TP we have chosen a 4-tuple to uniquely
   identify a MPLS-TP LSP.  This is composed of a Source Node_ID,
   Destination Node_ID, Tunnel_Nbr, and LSP_Nbr. The terms Source and
   Destination in this context are used relative to the direction of the
   signalling.  Note that the Tunnel_ID MUST be unique within the
   context of the source.

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

   o  Tunnel Endpoint Address = Destination Node_ID

   o  Tunnel_ID = Tunnel_Nbr

   o  Extended Tunnel_ID = Source Node_ID

   o  Tunnel Sender Address = Source Node_ID

   o  LSP_ID = LSP_Nbr

   A important construct within MPLS_TP is a connection which is
   provided across a working and a protect LSP.  Note that RFC 4872 [7],
   "RSVP-TE Extensions for E2E GMPLS Recovery", requires that the
   working and protect LSP have the same identification except for the
   LSP_ID, which must be unique.  Within this document we will use the
   term Tunnel for the connection provided by the working and protect
   LSPs.

   Thus, a Protected MPLS-TP LSP within a single operator is uniquely
   identified by the 3-tuple, Source Node_ID, Destination Node_ID and
   Tunnel_Nbr. Similarly, an MPLS-TP LSP is uniquely identified by the
   4-tuple, Source Node_ID, Destination Node_ID, Tunnel_Nbr and LSP_Nbr.

   In situations where a tunnel or an LSP needs to be globally unique,
   this is accomplished by prefixing each of the source and destination
   Node_IDs with a operator's Global_ID.

   When an MPLS-TP LSP is configured, it MUST be assigned a unique
   Network_IF_ID at both the source and destination endpoints.  Further
   when a MPLS-TP Tunnel is configured, it too must be assigned a unique
   Network_IF_ID.  Thus a point-to-point tunnel with working and protect



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   LSPs will have a total of three Network_IF_IDs assigned at each of
   the source and destination.

5.2.  Pseudowire Identifiers

   Pseudowire signalling (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.  The AII 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 signalling.  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 signalled
   environment, the required convention in RFC 4447 is that at a
   particular endpoint, the AII associated with that endpoint comes
   first.


6.  Maintenance Identifiers

   In MPLS-TP a Maintenance Entity (ME) 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).  This section
   defines a means of uniquely identifying Maintenance Entities and
   uniquely defining MEPs and MIPs within the context of a Maintenance
   Entity.

6.1.  Maintenance Entity Identifiers

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

   A Maintenance Entity and an MPLS-TP Path are closely related by
   separate concepts.  A MPLS-TP Path is a transport entity.  It exists
   with or without an associated maintenance entity, e.g. when the LSP



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   is not monitored.

6.1.1.  IP Compatible ME-IDs

   In order to automatically generate MEP_IDs for MPLS-TP LSPs and
   Pseudowires we simply use the corresponding Path identifier.
   However, when encoded in a protocol such as in a TLV, a different
   type needs to be defined as the two identifiers are semantically
   different.

6.1.2.  ICC based ME-IDs

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

   In this case, the ME 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 ME ID code (UMC).

   The UMC MUST be unique within the organization identified by the ICC.

   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.

6.2.  Maintenance Points

   Maintenance points are uniquely associated with a maintenance entity.
   Within the context of a ME, 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 ME-IDs described above or implicitly by
   the label of the received OAM message.

6.3.  MEP_IDs for MPLS-TP LSPs and Tunnels

   [Note: See proposed changes to in the issues section]

   In order to automatically generate MEP_IDs for MPLS-TP Tunnels and
   LSPs, we simply use the Network_IF_ID assigned when they are
   configured.  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.  [Question: do we want two ACH TLV formats or
   do we just spend the extra 4 octets on all OAM]



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6.4.  MEP_IDs for Pseudowires

   In order to automatically generate MEP_IDs for PWs, we simply use the
   AII associated with that end of the PW.

6.5.  Maintenance Intermediate Point Identifiers

   At a cross connect point, in order to automatically generate MIP_IDs
   for MPLS-TP LSPs, we simply use the MEP_IDs of the two interfaces
   which are cross connected via the label bindings of the MPLS-TP LSP.
   Note that although by this mapping, the MEP and the MIP will
   syntactically identical, the semantics will be made clear by both the
   TLV encoding and the scoping of the identifier to its MPLS-TP Path.
   If only one MIP is configured, then the lower value MEP_ID is chosen.
   This ensures that MIP_IDs are unique within the scope of an ME-ID
   within a single operator.  When Tunnels, LSPs or PWs cross operator
   boundaries, MIP_IDs are made unique by pre-pending them with the
   operator's Global_ID.  [Question: do we want two formats or do we
   just spend the extra 4+ octets on all OAM].

   [Note: Note - it has been proposed that when there is just one MIP to
   use the Node-ID only - need to discuss encoding for this]


7.  Open issues

   1.  The lack of symmetry between the configuration of the "head" and
       "Tail" ends of an MPLS-TP LSP makes for difficulties in
       configuration and operational intuitiveness.  Further it leads to
       interoperability issues with other possible implementations of
       protection.  Finally there are issues with odd configurations
       with P2MP / MP2MP (2 endpoints on the same node) I've decided
       that the tunnel ID I previously proposed really should be
       changed.  I propose to make it more like the PW-ID

          So instead of

          [Src-Global-ID]::Src-Node-ID::[Dst-Global-ID]:: Dst-Node-
          ID::Tunnel-nbr

          It would be

          [Src-Global-ID]::Src-Node-ID::Src-Tunnel-nbr:: [Dst-Global-
          ID]::Dst-Node-ID::Dst-Tunnel-nbr

          Likewise the Path-ID would go from





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          [Src-Global-ID]::Src-Node-ID::[Dst-Global-ID]:: Dst-Node-
          ID::Tunnel-nbr::LSP-nbr

          to

          [Src-Global-ID]::Src-Node-ID::Src-Tunnel-nbr::Src-LSP-nbr::
          [Dst-Global-ID]::Dst-Node-ID::Dst-Tunnel-nbr::Dst-LSP-nbr

          I would also change the IF-IDs and MEPs to

          Tunnel

          [Src-Global-ID]::Src-Node-ID::Src-Tunnel-nbr

          Path

          [Src-Global-ID]::Src-Node-ID::Src-Tunnel-nbr::Src-LSP-nbr

   2.  Can we do away with tunnel IDs all together and just use the IDs
       of the Working Path instead (irrespective of whether it is active
       or not)

   3.  We have two means of identifying operators.  Should either be
       allowed in all cases or can we constain 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.

   4.  Details on MEP and MIP identifiers need discussion.

   5.  Additional ICC identifiers for other entities may be required

   6.  Do we need IPv6 identifiers as well?

   7.  Identifiers for P2MP entities

   8.  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.  Are there additional identifiers required for NMS functions?


8.  References




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8.1.  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
         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]   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.

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

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

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

   [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-06
         (work in progress), July 2009.





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8.2.  Informative References

   [13]  Vigoureux, M., Ward, D., and M. Betts, "Requirements for OAM in
         MPLS Transport Networks",
         draft-ietf-mpls-tp-oam-requirements-02 (work in progress),
         June 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-09 (work in progress),
         June 2009.

   [16]  Bocci, M., Bryant, S., and L. Levrau, "A Framework for MPLS in
         Transport Networks", draft-ietf-mpls-tp-framework-02 (work in
         progress), July 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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