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].
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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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