Network Working Group Christian Martin
INTERNET DRAFT Verizon Global Networks,
Inc
Expiration Date: October, 2001 April 2001
Administrative Tags in IS-IS
<draft-martin-isis-admin-tags-00.txt>
Status
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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-
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1.0 Abstract
This document describes an extension to the IS-IS protocol to add
operational capabilities that allow for easier management of and
control over IP prefix distribution within an IS-IS domain. The
IS-IS protocol is specified in [1], with extensions for supporting
IPv4 specified in [2] and further enhancements for Traffic Engineering[4]
in [3].
This document enhances the IS-IS protocol by extending the
information that a Intermediate System (IS) [router] can place in
Link State Protocol Data Units (LSPs) as specified in [2]. This
information may be of use to operators who must control the way
IP prefix information is distributed throughout a multi-level, large
scale IS-IS topology.
2. 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 [4].
3.0 Introduction
As defined in [2] and extended in [3], the IS-IS protocol may be used
to distribute IP prefix reachibility information throughout an IS-IS
domain. The IP prefix information is encoded as TLV type 130 in [2],
with additional information carried in TLV 135 as specified in [3].
In particular, the extended IP Reachibilty TLV (135) contains support
for a larger metric space, an up/down bit to indicate redistribution
between different levels in the hierarchy, the IP prefix, and one or
more sub-TLVs that can be used to carry specific information about the
prefix. As of this writing no sub-TLVs have been defined; however, this
draft proposes two new sub-TLVs that may be used to carry administrative
information about an IP prefix.
This document is a publication of the IS-IS Working Group within the
IETF, and is a contribution to ISO IEC JTC1/SC6, for eventual
inclusion with ISO 10589.
4.0 Sub-TLV Additions
This draft proposes a new "Administrative Tag" sub-TLV to be added
to TLV 135. This TLV specifies a 32 bit unsigned integer that may be
associated with an IP prefix. One use for this tag would be for
controlling redistribution between areas, different routing protocols,
or multiple instances of IS-IS running on the same router. The methods
for which their use is implemented is beyond the scope of this document
and is left to the operators of IS-IS networks to decide. It is assumed,
however, that vendors will provide tools to match and set these tags
in routing policy configuration tools. The encoding of this new TLV is
as follows:
4.1 Sub-TLV <?>: Administrative Tag
This sub-TLV shall be used to associate an integer value with an IP
prefix such that it may be used in routing policy to control the
distribution of routing information within an IS-IS domain. The
Administrative Tag shall be encoded as a 4 octet unsigned integer.
5.0 Security Considerations
This document raises no new security issues for IS-IS, as any annotations
to IP prefixes should not pass outside the administrative control of the
network operator of the IS-IS domain. Such an allowance would violate
the
spirit of Interior Gateway Protocols in general and IS-IS in particular.
6.0 Acknowledgments
The author would like to thank Henk Smit for clarifying the best place to
describe this new information, and Tony Li for useful comments on this
draft.
7.0 References
[1] ISO 10589, "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)" [Also republished as RFC 1142]
[2] RFC 1195, "Use of OSI IS-IS for routing in TCP/IP and dual
environments", R.W. Callon, Dec. 1990
[3] draft-ietf-isis-traffic-02.txt, "IS-IS extensions for Traffic
Engineering", T. Li, H. Smit, Sep. 2000
[4] RFC 2702, "Requirements for Traffic Engineering Over MPLS," D.
Awduche, J. Malcolm, J. Agogbua, M. O'Dell, and J. McManus, September
1999.
9.0 Author's Address
Christian Martin
Verizon Global Networks, Inc.
1880 Campus Commons Dr
Reston, VA 20191
Email: cmartin@verizongni.com
Voice: 1 (703) 2954394
Fax: 1 (703) 2954279
Expiration Date: October, 2001