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Versions: 00 01                                                         
   ISIS WG
   Internet Draft                                 Jean-Philippe Vasseur
                                                        Stefano Previdi
                                                          Cisco Systems

   Document: draft-vasseur-isis-link-attr-
   00.txt
   Expires: August 2004                                   February 2004


               Definition of an IS-IS Link Attribute sub-TLV

                    draft-vasseur-isis-link-attr-00.txt


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 [i].

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
        http://www.ietf.org/ietf/1id-abstracts.txt
   The list of Internet-Draft Shadow Directories can be accessed at
        http://www.ietf.org/shadow.html.


Abstract

   This document proposes the definition of a sub-TLV called ôlink-
   attributeö carried within the TLV 22 and used to flood some link
   characteristics.

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 [ii].




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Table of contents

   1. Introduction...................................................2
   2. Link-attributes sub-TLV format.................................2
   3. Interoperability with routers non supporting this capability...3
   4. Security considerations........................................3
   5. Intellectual Property Considerations...........................3
   6. Acknowledgments................................................4
   7. References.....................................................4
   Normative references..............................................4
   Informative references............................................4
   8. Author's Addresses.............................................4


1.
  Introduction

   [IS-IS] specifies the IS-IS protocol (ISO 10589) with extensions to
   support IPv4 in [IS-IS-IP]. A router advertises one or several Link
   State Protocol data units which are composed of variable length
   tuples called TLVs (Type-Length-Value).

   [IS-IS-TE] defines a set of new TLVs whose aims are to add more
   information about links characteristics, increase the range of IS-IS
   metrics and improve the encoding of IS-IS prefixes.

   This document defines a new sub-TLV named ôLink-attributesö carried
   within the extended IS reachability TLV (type 22) specified in [IS-
   IS-TE].

2.
  Link-attributes sub-TLV format

   The link-attribute sub-TLV is carried within the TLV 22 and has a
   format identical to the TLV format used by the Traffic Engineering
   Extensions for IS-IS [IS-IS-TE]: 1 octet of sub-type, 1 octet of
   length of the value field of the sub-TLV followed by a 16 set of bit
   flags.

   The Link-attribute sub-type is 19 (to be assigned by IANA) and has a
   length of 2 octets bit mask.

   This sub-TLV is OPTIONAL and MUST appear at most once.

   The following bits are defined:




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   0x01: ôLocal Protection Availableö. When set, this indicates that the
   link is protected by means of some local protection mechanism (e.g
   [FRR]).

   0x02: ôLocal protection in useö. When set, this indicates that the
   local protection for the link in question is currently active.

   Such link characteristics has several applications such as
   constrained shortest path computation for a Traffic Engineering Label
   Switched (TE LSP) path, triggering of specific actions in the context
   of IS-IS SPF computation.

   0x04: ôLink excluded from local protection pathö. When set, this link
   SHOULD not be included in any computation of a repair path by any
   other router in the routing area.

3.
  Interoperability with routers non supporting this capability

   There is no interoperability issue as a router not supporting the
   link-attribute sub-TLV MUST just silently ignore this sub-TLV.

4.
  Security considerations

   No new security issues are raised in this document.

5.
  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
   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.

   The IETF has been notified of intellectual property rights claimed in
   regard to some or all of the specification contained in this


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   document.  For more information consult the online list of claimed
   rights.


6.
  Acknowledgments

   The authors would like to thank Mike Shand for his comments.

7.
  References

Normative references

   [RFC] Bradner, S., "Key words for use in RFCs to Indicate Requirement
   Levels," RFC 2119.

   [IS-IS] "Intermediate System to Intermediate System Intra-Domain
   Routeing Exchange Protocol for use in Conjunction with the Protocol
   for Providing the Connectionless-mode Network Service (ISO 8473)",
   ISO 10589.

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

   [IS-IS-TE] H. Smit, T. Li, ôIs-IS extensions for traffic
   engineeringö, draft-ietf-isis-traffic, work in progress.

Informative references

   [FRR] Ping Pan, et al, "Fast Reroute Extensions to RSVP-TE for LSP
   Tunnels", draft-ietf-mpls-rsvp-lsp-fastreroute-03.txt, December 2003.


8.
  Author's Addresses

      Jean-Philippe Vasseur
      CISCO Systems, Inc.
      300 Beaver Brook
      Boxborough, MA 01719
      USA
      Email: jpv@cisco.com

      Stefano Previdi
      CISCO Systems, Inc.
      Via Del Serafico 200
      00142 - Roma
      ITALY
      Email: sprevidi@cisco.com




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