path: root/doc/rfc/rfc4972.txt

Network Working Group                                   JP. Vasseur, Ed.
Request for Comments: 4972                            Cisco Systems, Inc
Category: Standards Track                                JL. Leroux, Ed.
                                                          France Telecom
                                                             S. Yasukawa
                                                                     NTT
                                                              S. Previdi
                                                               P. Psenak
                                                      Cisco Systems, Inc
                                                               P. Mabbey
                                                                 Comcast
                                                               July 2007


       Routing Extensions for Discovery of Multiprotocol (MPLS)
   Label Switch Router (LSR) Traffic Engineering (TE) Mesh Membership

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   The setup of a full mesh of Multi-Protocol Label Switching (MPLS)
   Traffic Engineering (TE) Label Switched Paths (LSP) among a set of
   Label Switch Routers (LSR) is a common deployment scenario of MPLS
   Traffic Engineering either for bandwidth optimization, bandwidth
   guarantees or fast rerouting with MPLS Fast Reroute.  Such deployment
   may require the configuration of a potentially large number of TE
   LSPs (on the order of the square of the number of LSRs).  This
   document specifies Interior Gateway Protocol (IGP) routing extensions
   for Intermediate System-to-Intermediate System (IS-IS) and Open
   Shortest Path First (OSPF) so as to provide an automatic discovery of
   the set of LSRs members of a mesh in order to automate the creation
   of such mesh of TE LSPs.








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Table of Contents

   1. Introduction ....................................................2
   2. Definitions .....................................................3
      2.1. Conventions Used in This Document ..........................4
   3. Description of a TE Mesh-Group ..................................4
   4. TE-MESH-GROUP TLV Formats .......................................4
      4.1. OSPF TE-MESH-GROUP TLV Format ..............................4
      4.2. IS-IS TE-MESH-GROUP Sub-TLV Format .........................7
   5. Elements of Procedure ...........................................9
      5.1. OSPF .......................................................9
      5.2. IS-IS .....................................................10
   6. Backward Compatibility .........................................11
   7. IANA Considerations ............................................11
      7.1. OSPF ......................................................11
      7.2. IS-IS .....................................................11
   8. Security Considerations ........................................12
   9. Acknowledgements ...............................................12
   10. References ....................................................12
      10.1. Normative References .....................................12
      10.2. Informative References ...................................13

1.  Introduction

   There are two well-known approaches in deploying MPLS Traffic
   Engineering:

   (1) The so-called "strategic" approach that consists of setting up a
   full mesh of TE LSPs between a set of LSRs.

   (2) The so-called "tactical" approach, where a set of TE LSPs are
   provisioned on well-identified "hot spots" in order to alleviate a
   congestion resulting, for instance, from an unexpected traffic growth
   in some parts of the network.

   The setup of a full mesh of TE LSPs among a set of LSRs is a common
   deployment scenario of MPLS Traffic Engineering either for bandwidth
   optimization, bandwidth guarantees, or fast rerouting with MPLS Fast
   Reroute.  Setting up a full mesh of TE LSPs between N LSRs requires
   the configuration of a potentially large number of TE LSPs (O(N^2)).
   Furthermore, the addition of any new LSR in the mesh requires the
   configuration of N additional TE LSPs on the new LSR and one new TE
   LSP on every LSR of the existing mesh destined to this new LSR, which
   gives a total of 2*N TE LSPs to be configured.  Such an operation is
   not only time consuming but also risky (prone to misconfiguration)
   for Service Providers.  Hence, an automatic mechanism for setting up
   TE LSPs meshes is desirable and requires the ability to automatically
   discover the set of LSRs that belong to the mesh.  This document



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   specifies routing extensions so as to automatically discover the
   members of a mesh, also referred to as a "TE mesh-group".  Note that
   the mechanism(s) needed for the dynamic creation of TE LSPs is
   implementation specific and outside the scope of this document.

   Routing extensions have been defined in [RFC4970] and [RFC4971] in
   order to advertise router capabilities.  This document specifies IGP
   (OSPF and IS-IS) TE Mesh Group (Type Length Value) TLVs allowing for
   the automatic discovery of a TE mesh-group members, to be carried in
   the OSPF Router Information (Link State Advertisement) LSA [RFC4970]
   and IS-IS Router Capability TLV [RFC4971].  The routing extensions
   specified in this document provide the ability to signal multiple TE
   mesh groups.  An LSR may belong to more than one TE mesh-group(s).

   There are relatively tight real-time constraints on the operation of
   IGPs (such as OSPF and IS-IS).  For this reason, some care needs to
   be applied when proposing to carry additional information in an IGP.
   The information described in this document is both relatively small
   in total volume (compared with other information already carried in
   IGPs), and also relatively stable (i.e., changes are based on
   configuration changes, but not on dynamic events within the network,
   or on dynamic triggers, such as the leaking of information from other
   routing protocols or routing protocol instances).

2.  Definitions

   Terminology used in this document

   IGP: Interior Gateway Protocol

   IGP Area: OSPF area or IS-IS level

   IS-IS: Intermediate System-to-Intermediate System (IS-IS)

   LSR: Label Switch Router

   OSPF: Open Shortest Path First

   OSPF LSA: OSPF Link State Advertisement

   TE LSP: Traffic Engineering Label Switched Path

   TE LSP head-end: head/source of the TE LSP

   TE LSP tail-end: tail/destination of the TE LSP.

   TLV: Type Length Value




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2.1.  Conventions Used in This Document

   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 [RFC2119].

3.  Description of a TE Mesh-Group

   A TE mesh-group is defined as a group of LSRs that are connected by a
   full mesh of TE LSPs.  Routing extensions are specified in this
   document, allowing for dynamic discovery of the TE mesh-group
   members.  Procedures are also specified for a member to join and
   leave a TE mesh-group.  For each TE mesh-group membership announced
   by an LSR, the following information is advertised:

   -  A mesh-group number identifying the TE mesh-group that the LSR
      belongs to,

   -  A tail-end address (used as the TE LSP Tail-end address by other
      LSRs belonging to the same mesh-group),

   -  A tail-end name: a display string that is allocated to the tail-
      end used to ease the TE-LSP naming.

4.  TE-MESH-GROUP TLV Formats

4.1.  OSPF TE-MESH-GROUP TLV Format

   The TE-MESH-GROUP TLV is used to advertise the desire of an LSR to
   join/leave a given TE mesh-group.  No sub-TLV is currently defined
   for the TE-MESH-GROUP TLV.

   The OSPF TE-MESH-GROUP TLV (advertised in an OSPF router information
   LSA defined in [RFC4970]) has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Type             |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      //                            Value                            //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 1 - OSPF TE-MESH-GROUP TLV format





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   Where
      Type: identifies the TLV type
      Length: the length of the value field in octets

   The format of the OSPF TE-MESH-GROUP TLV is the same as the TLV
   format used by the Traffic Engineering Extensions to OSPF
   (see[RFC3630]).  The TLV is padded to a four-octet alignment; padding
   is not included in the length field (so a three-octet value would
   have a length of three, but the total size of the TLV would be eight
   octets).  Nested TLVs are also 32-bit aligned.  Unrecognized types
   are ignored.  All types between 32768 and 65535 are reserved for
   vendor-specific extensions.  All other undefined type codes are
   reserved for future assignment by IANA.

   The OSPF TE-MESH-GROUP TLV format for IPv4 (Figure 2) and IPv6
   (Figure 3) is as follows:

   TYPE: 3
   LENGTH: Variable

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      mesh-group-number 1                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Tail-end IPv4 address 1                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Name length  |               Tail-end name 1                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //                                                               //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      mesh-group-number n                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Tail-end IPv4 address n                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Name length  |               Tail-end name n                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 2 - OSPF TE-MESH-GROUP TLV format (IPv4 Address)












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   TYPE: 4
   LENGTH: Variable

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    mesh-group-number 1                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                   Tail-end IPv6 address 1                     |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Name length  |             Tail-end name 1                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //                                                               //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    mesh-group-number n                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                   Tail-end IPv6 address n                     |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Name length  |             Tail-end name n                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 3 - OSPF TE-MESH-GROUP TLV format (IPv6 Address)

   The OSPF TE-MESH-GROUP TLV may contain one or more mesh-group
   entries, where each entry corresponds to a TE mesh-group and is made
   of the following fields:

   -  A mesh-group-number that identifies the mesh-group number.

   -  A Tail-end address: an IPv4 or IPv6 IP address to be used as a
      tail-end TE LSP address by other LSRs belonging to the same mesh-
      group.

   -  Name length field: An integer, expressed in octets, that indicates
      the length of the Tail-end name before padding.

   -  A Tail-end name: A display string that is allocated to the Tail-
      end.  The field is of variable length field and is used to
      facilitate the TE LSP identification.






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4.2.  IS-IS TE-MESH-GROUP Sub-TLV Format

   The TE-MESH-GROUP sub-TLV is used to advertise the desire of an LSR
   to join/leave a given TE mesh-group.  No sub-TLV is currently defined
   for the TE-MESH-GROUP sub-TLV.

   The IS-IS TE-MESH-GROUP sub-TLV (advertised in the IS-IS CAPABILITY
   TLV defined in [RFC4971]) is composed of 1 octet for the type, 1
   octet specifying the TLV length and a value field.  The format of the
   TE-MESH-GROUP sub-TLV is identical to the TLV format used by the
   Traffic Engineering Extensions for IS-IS [RFC3784].

   The IS-IS TE-MESH-GROUP sub-TLV format for IPv4 (Figure 4) and IPv6
   (Figure 5) is as follows:

   TYPE: 3
   LENGTH: Variable
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     mesh-group-number 1                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Tail-end IPv4 address  1                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Name length  |             Tail-end name 1                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //                                                               //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     mesh-group-number n                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Tail-end IPv4 address n                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Name length  |             Tail-end name n                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 4 - IS-IS TE-MESH-GROUP sub-TLV format (IPv4 Address)















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   TYPE: 4
   LENGTH: Variable

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      mesh-group-number 1                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                    Tail-end IPv6 address 1                    |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Name length  |            Tail-end name 1                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //                                                               //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      mesh-group-number n                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                    Tail-end IPv6 address n                    |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Name length  |            Tail-end name n                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 5 - IS-IS TE-MESH-GROUP sub-TLV format (IPv6 Address)

   The IS-IS TE-MESH-GROUP sub-TLV may contain one or more mesh-group
   entries where each entry correspond to a TE mesh-group and is made of
   the following fields:

   -  A mesh-group-number that identifies the mesh-group number.

   -  A Tail-end address: an IPv4 or IPv6 IP address to be used as a
      tail-end TE LSP address by other LSRs belonging to the same mesh-
      group.

   -  Name length field: An integer, expressed in octets, that indicates
      the length of the Tail-end name before padding.

   -  A Tail-end name: A display string that is allocated to the Tail-
      end.  The field is of variable length and is used to facilitate
      the TE LSP identification.






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5.  Elements of Procedure

   The OSPF TE-MESH-GROUP TLV is carried within the OSPF Routing
   Information LSA and the IS-IS TE-MESH-GROUP sub-TLV is carried within
   the IS-IS Router capability TLV.  As such, elements of procedure are
   inherited from those defined in [RFC4970] and [RFC4971] for OSPF and
   IS-IS respectively.  Specifically, a router MUST originate a new
   LSA/LSP whenever the content of this information changes, or whenever
   required by regular routing procedure (e.g., updates).

   The TE-MESH-GROUP TLV is OPTIONAL and MUST NOT include more than one
   of each of the IPv4 instances or the IPv6 instance.  If either the
   IPv4 or the IPv6 OSPF TE-MESH-GROUP TLV occurs more than once within
   the OSPF Router Information LSA, only the first instance is
   processed, subsequent TLV(s) SHOULD be silently ignored.  Similarly,
   if either the IPv4 or the IPv6 IS-IS TE-MESH-GROUP sub-TLV occurs
   more than once within the IS-IS Router capability TLV, only the first
   instance is processed, subsequent TLV(s) SHOULD be silently ignored.

5.1.  OSPF

   The TE-MESH-GROUP TLV is advertised within an OSPF Router Information
   opaque LSA (opaque type of 4, opaque ID of 0) for OSPFv2 [RFC2328]
   and within a new LSA (Router Information LSA) for OSPFv3 [RFC2740].
   The Router Information LSAs for OSPFv2 and OSPFv3 are defined in
   [RFC4970].

   A router MUST originate a new OSPF router information LSA whenever
   the content of any of the advertised TLV changes or whenever required
   by the regular OSPF procedure (LSA update (every LSRefreshTime)).  If
   an LSR desires to join or leave a particular TE mesh group, it MUST
   originate a new OSPF Router Information LSA comprising the updated
   TE-MESH-GROUP TLV.  In the case of a join, a new entry will be added
   to the TE-MESH-GROUP TLV; conversely, if the LSR leaves, a mesh-group
   the corresponding entry will be removed from the TE-MESH-GROUP TLV.
   Note that both operations can be performed in the context of a single
   LSA update.  An implementation SHOULD be able to detect any change to
   a previously received TE-MESH-GROUP TLV from a specific LSR.

   As defined in [RFC2370] for OSPVv2 and in [RFC2740] for OSPFv3, the
   flooding scope of the Router Information LSA is determined by the LSA
   Opaque type for OSPFv2 and the values of the S1/S2 bits for OSPFv3.

   For OSPFv2 Router Information opaque LSA:

   -  Link-local scope: type 9;

   -  Area-local scope: type 10;



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   -  Routing-domain scope: type 11.  In this case, the flooding scope
      is equivalent to the Type 5 LSA flooding scope.

   For OSPFv3 Router Information LSA:

   -  Link-local scope: OSPFv3 Router Information LSA with the S1 and S2
      bits cleared;

   -  Area-local scope: OSPFv3 Router Information LSA with the S1 bit
      set and the S2 bit cleared;

   -  Routing-domain scope: OSPFv3 Router Information LSA with S1 bit
      cleared and the S2 bit set.

   A router may generate multiple OSPF Router Information LSAs with
   different flooding scopes.

   The TE-MESH-GROUP TLV may be advertised within an Area-local or
   Routing-domain scope Router Information LSA, depending on the MPLS TE
   mesh group profile:

   -  If the MPLS TE mesh-group is contained within a single area (all
      the LSRs of the mesh-group are contained within a single area),
      the TE-MESH-GROUP TLV MUST be generated within an Area-local
      Router Information LSA.

   -  If the MPLS TE mesh-group spans multiple OSPF areas, the TE mesh-
      group TLV MUST be generated within a Routing-domain scope router
      information LSA.

5.2.  IS-IS

   The TE-MESH-GROUP sub-TLV is advertised within the IS-IS Router
   CAPABILITY TLV defined in [RFC4971].  An IS-IS router MUST originate
   a new IS-IS LSP whenever the content of any of the advertised sub-TLV
   changes or whenever required by regular IS-IS procedure (LSP
   updates).  If an LSR desires to join or leave a particular TE mesh
   group, it MUST originate a new LSP comprising the refreshed IS-IS
   Router capability TLV comprising the updated TE-MESH-GROUP sub-TLV.
   In the case of a join, a new entry will be added to the TE-MESH-GROUP
   sub-TLV; conversely, if the LSR leaves a mesh-group, the
   corresponding entry will be deleted from the TE-MESH-GROUP sub-TLV.
   Note that both operations can be performed in the context of a single
   update.  An implementation SHOULD be able to detect any change to a
   previously received TE-MESH-GROUP sub-TLV from a specific LSR.

   If the flooding scope of a TE-MESH-GROUP sub-TLV is limited to an
   IS-IS level/area, the sub-TLV MUST not be leaked across level/area



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   and the S flag of the Router CAPABILITY TLV MUST be cleared.
   Conversely, if the flooding scope of a TE-MESH-GROUP sub-TLV is the
   entire routing domain, the TLV MUST be leaked across IS-IS
   levels/areas, and the S flag of the Router CAPABILITY TLV MUST be
   set.  In both cases, the flooding rules specified in [RFC4971] apply.

   As specified in [RFC4971], a router may generate multiple IS-IS
   Router CAPABILITY TLVs within an IS-IS LSP with different flooding
   scopes.

6.  Backward Compatibility

   The TE-MESH-GROUP TLVs defined in this document do not introduce any
   interoperability issue.  For OSPF, a router not supporting the TE-
   MESH-GROUP TLV SHOULD just silently ignore the TLV as specified in
   [RFC2370].  For an IS-IS, a router not supporting the TE-MESH-GROUP
   sub-TLV SHOULD just silently ignore the sub-TLV.

7.  IANA Considerations

7.1.  OSPF

   The registry for the Router Information LSA is defined in [RFC4970].
   IANA assigned a new OSPF TLV code-point for the TE-MESH-GROUP TLVs
   carried within the Router Information LSA.

   Value      Sub-TLV                   References
   -----     --------                   ----------
     3    TE-MESH-GROUP TLV (IPv4)      RFC 4972 (this doc)
     4    TE-MESH-GROUP TLV (IPv6)      RFC 4972 (this doc)

7.2.  IS-IS

   The registry for the Router Capability TLV is defined in [RFC4971].
   IANA assigned a new IS-IS sub-TLV code-point for the TE-MESH-GROUP
   sub-TLVs carried within the IS-IS Router Capability TLV.

   Value      Sub-TLV                  References
   -----      --------                 ----------
     3    TE-MESH-GROUP TLV (IPv4)     RFC 4972 (this doc)
     4    TE-MESH-GROUP TLV (IPv6)     RFC 4972 (this doc)










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8.  Security Considerations

   The function described in this document does not create any new
   security issues for the OSPF and IS-IS protocols.  Security
   considerations are covered in [RFC2328] and [RFC2740] for the base
   OSPF protocol and in [RFC1195] for IS-IS.  It must be noted that the
   advertisement of "fake" TE Mesh Group membership(s) by a mis-
   configured or malicious LSR Y would not have any major impact on the
   network (other than overloading the IGP), such as triggering the set
   up of new MPLS TE LSP: indeed, for a new TE LSP originated by another
   LSR X destined to LSR Y to be set up, the same TE Mesh group
   membership must be configured on both LSRs.  Thus such fake
   advertisement could not amplify any Denial of Service (DoS) attack.

9.  Acknowledgements

   We would like to thank Dean Cheng, Adrian Farrel, Yannick Le Louedec,
   Dave Ward, Les Ginsberg, Stephen Nadas, Acee Lindem, Dimitri
   Papadimitriou, and Lakshminath Dondeti for their useful comments.

10.  References

10.1.  Normative References

   [RFC4971]  Vasseur, J-P., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
              "Intermediate System to Intermediate System (IS-IS)
              Extensions for Advertising Router Information", RFC 4971,
              July 2007.

   [RFC4970]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
              S. Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 4970, July 2007.

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, December 1990.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [RFC2370]  Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, July
              1998.

   [RFC2740]  Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC
              2740, December 1999.





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10.2.  Informative References

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630, September
              2003.

   [RFC3784]  Smit, H. and T. Li, "Intermediate System to Intermediate
              System (IS-IS) Extensions for Traffic Engineering (TE)",
              RFC 3784, June 2004.

Authors' Addresses

   JP Vasseur (editor)
   Cisco Systems, Inc
   1414 Massachusetts Avenue
   Boxborough, MA  01719
   USA

   EMail: jpv@cisco.com


   JL Le Roux (editor)
   France Telecom
   2, Avenue Pierre-Marzin
   Lanion,   22307
   FRANCE

   EMail: jeanlouis.leroux@orange-ftgroup.com


   Seisho Yasukawa
   NTT
   3-1, Otemachi 2-Chome Chiyoda-ku
   Tokyo,   100-8116
   JAPAN

   EMail: s.yasukawa@hco.ntt.co.jp


   Stefano Previdi
   Cisco Systems, Inc
   Via Del Serafico 200
   Roma,   00142
   Italy

   EMail: sprevidi@cisco.com





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RFC 4972        Discovery of MPLS LSR TE Mesh Membership       July 2007


   Peter Psenak
   Cisco Systems
   Mlynske Nivy 43
   821 09
   Bratislava
   Slovakia

   EMail: ppsenak@cisco.com


   Paul Mabbey
   Comcast Cable
   4100 E. Dry Creek Rd
   Centennial, CO 80122
   USA

   EMail: Paul_Mabey@cable.comcast.com


































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RFC 4972        Discovery of MPLS LSR TE Mesh Membership       July 2007


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