Network Working Group JP. Vasseur, Ed.
Request for Comments: 4971 N. Shen, Ed.
Category: Standards Track Cisco Systems, Inc.
R. Aggarwal, Ed.
Juniper Networks
July 2007
Intermediate System to Intermediate System (IS-IS) Extensions
for Advertising Router Information
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
This document defines a new optional Intermediate System to
Intermediate System (IS-IS) TLV named CAPABILITY, formed of multiple
sub-TLVs, which allows a router to announce its capabilities within
an IS-IS level or the entire routing domain.
Table of Contents
1. Introduction ....................................................2
1.1. Conventions Used in This Document ..........................2
2. IS-IS Router CAPABILITY TLV .....................................3
3. Elements of Procedure ...........................................4
4. Interoperability with Routers Not Supporting the
Capability TLV ..................................................5
5. Security Considerations .........................................6
6. IANA Considerations .............................................6
7. Acknowledgment ..................................................6
8. References ......................................................6
8.1. Normative References .......................................6
8.2. Informative References .....................................8
Vasseur, et al. Standards Track [Page 1]
RFC 4971 IS-IS Extensions for Advertising Router Info July 2007
1. Introduction
There are several situations where it is useful for the IS-IS [IS-IS]
[IS-IS-IP] routers to learn the capabilities of the other routers of
their IS-IS level, area, or routing domain. For the sake of
illustration, three examples related to MPLS Traffic Engineering (TE)
are described here:
1. Mesh-group: the setting up of a mesh of TE Label Switched Paths
(LSPs) [IS-IS-TE] requires some significant configuration effort.
[AUTOMESH] proposes an auto-discovery mechanism whereby every
Label Switching Router (LSR) of a mesh advertises its mesh-group
membership by means of IS-IS extensions.
2. Point to Multipoint TE LSP (P2MP LSP). A specific sub-TLV
([TE-NODE-CAP]) allows an LSR to advertise its Point To Multipoint
capabilities ([P2MP] and [P2MP-REQS]).
3. Inter-area traffic engineering: Advertisement of the IPv4 and/or
the IPv6 Traffic Engineering Router IDs.
The use of IS-IS for Path Computation Element (PCE) discovery may
also be considered and will be discussed in the PCE WG.
The capabilities mentioned above require the specification of new
sub-TLVs carried within the CAPABILITY TLV defined in this document.
Note that the examples above are provided for the sake of
illustration. This document proposes a generic capability
advertising mechanism that is not limited to MPLS Traffic
Engineering.
This document defines a new optional IS-IS TLV named CAPABILITY,
formed of multiple sub-TLVs, which allows a router to announce its
capabilities within an IS-IS level or the entire routing domain. The
applications mentioned above require the specification of new sub-
TLVs carried within the CAPABILITY TLV defined in this document.
Definition of these sub-TLVs is outside the scope of this document.
1.1. 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 [RFC-2119].
Vasseur, et al. Standards Track [Page 2]
RFC 4971 IS-IS Extensions for Advertising Router Info July 2007
2. IS-IS Router CAPABILITY TLV
The IS-IS Router CAPABILITY TLV is composed of 1 octet for the type,
datatracker.ietf.org