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rfc:rfc3477

Network Working Group K. Kompella Request for Comments: 3477 Y. Rekhter Category: Standards Track Juniper Networks

                                                          January 2003
   Signalling Unnumbered Links in Resource ReSerVation Protocol -
                   Traffic Engineering (RSVP-TE)

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 Internet Society (2003).  All Rights Reserved.

Abstract

 Current signalling used by Multi-Protocol Label Switching Traffic
 Engineering (MPLS TE) does not provide support for unnumbered links.
 This document defines procedures and extensions to Resource
 ReSerVation Protocol (RSVP) for Label Switched Path (LSP) Tunnels
 (RSVP-TE), one of the MPLS TE signalling protocols, that are needed
 in order to support unnumbered links.

Specification of Requirements

 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 BCP 14, RFC 2119
 [RFC2119].

1. Overview

 Supporting MPLS TE over unnumbered links (i.e., links that do not
 have IP addresses) involves two components: (a) the ability to carry
 (TE) information about unnumbered links in IGP TE extensions (ISIS or
 OSPF), and (b) the ability to specify unnumbered links in MPLS TE
 signalling.  The former is covered in [GMPLS-ISIS, GMPLS-OSPF].  The
 focus of this document is on the latter.

Kompella & Rekhter Standards Track [Page 1] RFC 3477 Signalling Unnumbered Links in RSVP-TE January 2003

 Current signalling used by MPLS TE does not provide support for
 unnumbered links because the current signalling does not provide a
 way to indicate an unnumbered link in its Explicit Route and Record
 Route Objects.  This document proposes simple procedures and
 extensions that allow RSVP-TE signalling [RFC3473] to be used with
 unnumbered links.

2. Link Identifiers

 An unnumbered link has to be a point-to-point link.  An LSR at each
 end of an unnumbered link assigns an identifier to that link.  This
 identifier is a non-zero 32-bit number that is unique within the
 scope of the LSR that assigns it.  If one is using OSPF or ISIS as
 the IGP in support of traffic engineering, then the IS-IS and/or OSPF
 and RSVP modules on an LSR must agree on the identifiers.
 There is no a priori relationship between the identifiers assigned to
 a link by the LSRs at each end of that link.
 LSRs at the two end points of an unnumbered link exchange with each
 other the identifiers they assign to the link.  Exchanging the
 identifiers may be accomplished by configuration, by means of a
 protocol such as LMP ([LMP]), by means of RSVP/CR-LDP (especially in
 the case where a link is a Forwarding Adjacency, see below), or by
 means of IS-IS or OSPF extensions ([ISIS-GMPLS], [OSPF-GMPLS]).
 Consider an (unnumbered) link between LSRs A and B.  LSR A chooses an
 identifier for that link.  So does LSR B.  From A's perspective, we
 refer to the identifier that A assigned to the link as the "link
 local identifier" (or just "local identifier"), and to the identifier
 that B assigned to the link as the "link remote identifier" (or just
 "remote identifier").  Likewise, from B's perspective, the identifier
 that B assigned to the link is the local identifier, and the
 identifier that A assigned to the link is the remote identifier.
 In the context of this document the term "Router ID" means a stable
 IP address of an LSR that is always reachable if there is any
 connectivity to the LSR.  This is typically implemented as a
 "loopback address"; the key attribute is that the address does not
 become unusable if an interface on the LSR is down.  In some cases
 this value will need to be configured.  If one is using the OSPF or
 ISIS as the IGP in support of traffic engineering, then it is
 RECOMMENDED for the Router ID to be set to the "Router Address" as
 defined in [OSPF-TE], or "Traffic Engineering Router ID" as defined
 in [ISIS-TE].
 This section is equally applicable to the case of unnumbered
 component links (see [LINK-BUNDLE]).

Kompella & Rekhter Standards Track [Page 2] RFC 3477 Signalling Unnumbered Links in RSVP-TE January 2003

3. Unnumbered Forwarding Adjacencies

 If an LSR that originates an LSP advertises this LSP as an unnumbered
 Forwarding Adjacency in IS-IS or OSPF (see [LSP-HIER]), or the LSR
 uses the Forwarding Adjacency formed by this LSP as an unnumbered
 component link of a bundled link (see [LINK-BUNDLE]), the LSR MUST
 allocate an identifier to that Forwarding Adjacency (just like for
 any other unnumbered link).  Moreover, the Path message used for
 establishing the LSP that forms the Forwarding Adjacency MUST contain
 the LSP_TUNNEL_INTERFACE_ID object (described below), with the LSR's
 Router ID set to the head end's Router ID, and the Interface ID set
 to the identifier that the LSR allocated to the Forwarding Adjacency.
 If the Path message contains the LSP_TUNNEL_INTERFACE_ID object, then
 the tail-end LSR MUST allocate an identifier to that Forwarding
 Adjacency (just like for any other unnumbered link).  Furthermore,
 the Resv message for the LSP MUST contain an LSP_TUNNEL_INTERFACE_ID
 object, with the LSR's Router ID set to the tail-end's Router ID, and
 the Interface ID set to the identifier allocated by the tail-end LSR.
 For the purpose of processing the ERO and the IF_ID RSVP_HOP objects,
 an unnumbered Forwarding Adjacency is treated as an unnumbered (TE)
 link or an unnumbered component link as follows.  The LSR that
 originates the Adjacency sets the link local identifier for that link
 to the value that the LSR allocates to that Forwarding Adjacency, and
 the link remote identifier to the value carried in the Interface ID
 field of the Reverse Interface ID object.  The LSR that is a tail-end
 of that Forwarding Adjacency sets the link local identifier for that
 link to the value that the LSR allocates to that Forwarding
 Adjacency, and the link remote identifier to the value carried in the
 Interface ID field of the Forward Interface ID object.

3.1. LSP_TUNNEL_INTERFACE_ID Object

 The LSP_TUNNEL_INTERFACE_ID object has a class number of of 193, C-
 Type of 1 and length of 12.  The format is given below.
 Figure 1: LSP_TUNNEL_INTERFACE_ID Object
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        LSR's Router ID                        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    Interface ID (32 bits)                     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Kompella & Rekhter Standards Track [Page 3] RFC 3477 Signalling Unnumbered Links in RSVP-TE January 2003

 This object can optionally appear in either a Path message or a Resv
 message.  In the former case, we call it the "Forward Interface ID"
 for that LSP; in the latter case, we call it the "Reverse Interface
 ID" for the LSP.

4. Signalling Unnumbered Links in EROs

 A new subobject of the Explicit Route Object (ERO) is used to specify
 unnumbered links.  This subobject has the following format:
 Figure 2: Unnumbered Interface ID Subobject
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |L|    Type     |     Length    |    Reserved (MUST be zero)    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                           Router ID                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Interface ID (32 bits)                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The Type is 4 (Unnumbered Interface ID).  The Length is 12.
 The Interface ID is the identifier assigned to the link by the LSR
 specified by the router ID.

4.1. Processing the IF_ID RSVP_HOP object

 When an LSR receives a Path message containing the IF_ID RSVP_HOP
 object (see [RFC3473], [RFC3471]) with the IF_INDEX TLV, the LSR
 processes this TLV as follows.  The LSR must have information about
 the identifiers assigned by its neighbors to the unnumbered links
 between the neighbors and the LSR.  The LSR uses this information to
 find a link with tuple <Router ID, local identifier> matching the
 tuple <IP Address, Interface ID> carried in the IF_INDEX TLV.  If the
 matching tuple is found, the match identifies the link for which the
 LSR has to perform label allocation.
 Otherwise, the LSR SHOULD return an error using the IF_ID ERROR_SPEC
 object (see [RFC3473], [RFC3471]).  The Error code in the object is
 set to 24.  The Error value in the object is set to 16.

4.2. Processing the ERO

 The Unnumbered Interface ID subobject is defined to be a part of a
 particular abstract node if that node has the Router ID that is equal
 to the Router ID field in the subobject, and if the node has an

Kompella & Rekhter Standards Track [Page 4] RFC 3477 Signalling Unnumbered Links in RSVP-TE January 2003

 (unnumbered) link or an (unnumbered) Forwarding Adjacency whose local
 identifier (from that node's point of view) is equal to the value
 carried in the Interface ID field of the subobject.
 With this in mind, the ERO processing in the presence of the
 Unnumbered Interface ID subobject follows the rules specified in
 section 4.3.4.1 of [RFC3209].
 As part of the ERO processing, or to be more precise, as part of the
 next hop selection, if the outgoing link is unnumbered, the Path
 message that the node sends to the next hop MUST include the IF_ID
 RSVP_HOP object, with the IP address field of that object set to the
 Router ID of the node, and the Interface ID field of that object set
 to the identifier assigned to the link by the node.

5. Record Route Object

 A new subobject of the Record Route Object (RRO) is used to record
 that the LSP path traversed an unnumbered link.  This subobject 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    |     Flags     | Reserved (MBZ)|
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                           Router ID                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Interface ID (32 bits)                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The Type is 4 (Unnumbered Interface ID); the Length is 12.  Flags are
 defined below.
 0x01  Local protection available
    Indicates that the link downstream of this node is protected via a
    local repair mechanism.  This flag can only be set if the Local
    protection flag was set in the SESSION_ATTRIBUTE object of the
    corresponding Path message.
 0x02  Local protection in use
    Indicates that a local repair mechanism is in use to maintain this
    tunnel (usually in the face of an outage of the link it was
    previously routed over).

Kompella & Rekhter Standards Track [Page 5] RFC 3477 Signalling Unnumbered Links in RSVP-TE January 2003

5.1. Handling RRO

 If at an intermediate node (or at the head-end), the ERO subobject
 that was used to determine the next hop is of type Unnumbered
 Interface ID, and a RRO object was received in the Path message (or
 is desired in the original Path message), an RRO subobject of type
 Unnumbered Interface ID MUST be appended to the received RRO when
 sending a Path message downstream.
 If the ERO subobject that was used to determine the next hop is of
 any other type, the handling procedures of [RFC3209] apply.  Also, if
 Label Recording is desired, the procedures of [RFC3209] apply.

6. Security Considerations

 This document makes a small extension to RFC 3209 [RFC3209] to refine
 and explicate the use of unnumbered links.  As such it poses no new
 security concerns.  In fact, one might argue that use of the extra
 interface identify could make an RSVP message harder to spoof.

7. IANA Considerations

 The IANA assigns values to RSVP protocol parameters.  The current
 document defines a new subobject for the EXPLICIT_ROUTE object and
 for the ROUTE_RECORD object.  The rules for the assignment of
 subobject numbers have been defined in [RFC3209], using the
 terminology of BCP 26, RFC 2434, "Guidelines for Writing an IANA
 Considerations Section in RFCs".  Those rules apply to the assignment
 of subobject numbers for the new subobject of the EXPLICIT_ROUTE and
 ROUTE_RECORD objects.
 Furthermore, the same Internet authority needs to assign a class
 number to the LSP_TUNNEL_INTERFACE_ID object.  This must be of the
 form 11bbbbbb (i.e., RSVP silently ignores this unknown object but
 forwards it).

8. Intellectual Property Considerations

 The IETF takes no position regarding the validity or scope of any
 intellectual property or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; neither does it represent that it
 has made any effort to identify any such rights.  Information on the
 IETF's procedures with respect to rights in standards-track and
 standards-related documentation can be found in BCP-11.  Copies of
 claims of rights made available for publication and any assurances of
 licenses to be made available, or the result of an attempt made to

Kompella & Rekhter Standards Track [Page 6] RFC 3477 Signalling Unnumbered Links in RSVP-TE January 2003

 obtain a general license or permission for the use of such
 proprietary rights by implementors or users of this specification can
 be obtained from the IETF Secretariat.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights which may cover technology that may be required to practice
 this standard.  Please address the information to the IETF Executive
 Director.

9. Acknowledgments

 Thanks to Lou Berger and Markus Jork for pointing out that the RRO
 should be extended in like fashion to the ERO.  Thanks also to Rahul
 Aggarwal and Alan Kullberg for their comments on the text.  Finally,
 thanks to Bora Akyol, Vach Kompella, and George Swallow.

10. References

10.1. Normative references

 [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3209]     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.
 [RFC3471]     Berger, L., Editor, "Generalized Multi-Protocol Label
               Switching (MPLS) Signaling Functional Description", RFC
               3471, January 2003.
 [RFC3473]     Berger, L., Editor, "Generalized Multi-Protocol Label
               Switching (MPLS) Signaling Resource ReserVation
               Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
               3473, January 2003.

10.2. Non-normative references

 [GMPLS-ISIS]  Kompella, K., Rekhter, Y., Banerjee, A. et al., "IS-IS
               Extensions in Support of Generalized MPLS", Work in
               Progress.
 [GMPLS-OSPF]  Kompella, K., Rekhter, Y., Banerjee, A. et al., "OSPF
               Extensions in Support of Generalized MPLS", Work in
               Progress.

Kompella & Rekhter Standards Track [Page 7] RFC 3477 Signalling Unnumbered Links in RSVP-TE January 2003

 [ISIS-TE]     Li, T. and H. Smit, "IS-IS extensions for Traffic
               Engineering", Work in Progress.
 [LINK-BUNDLE] Kompella, K., Rekhter, Y. and L. Berger, "Link Bundling
               in MPLS Traffic Engineering", Work in Progress.
 [LSP-HIER]    Kompella, K. and Y. Rekhter, "LSP Hierarchy with MPLS
               TE", Work in Progress.
 [LMP]         Lang, J., Mitra, K., et al., "Link Management Protocol
               (LMP)", Work in Progress.
 [OSPF-TE]     Katz, D., Yeung, D., Kompella, K., "Traffic Engineering
               Extensions to OSPF Version 2", Work in Progress.

11. Authors' Addresses

 Kireeti Kompella
 Juniper Networks, Inc.
 1194 N. Mathilda Ave.
 Sunnyvale, CA 94089
 EMail: kireeti@juniper.net
 Yakov Rekhter
 Juniper Networks, Inc.
 1194 N. Mathilda Ave.
 Sunnyvale, CA 94089
 EMail: yakov@juniper.net

Kompella & Rekhter Standards Track [Page 8] RFC 3477 Signalling Unnumbered Links in RSVP-TE January 2003

12. Full Copyright Statement

 Copyright (C) The Internet Society (2003).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Kompella & Rekhter Standards Track [Page 9]

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