RFC 2966 (rfc2966) - Page 1 of 14


Domain-wide Prefix Distribution with Two-Level IS-IS



Alternative Format: Original Text Document



Network Working Group                                              T. Li
Request for Comments: 2966                              Procket Networks
Category: Informational                                    T. Przygienda
                                                                 Redback
                                                                 H. Smit
                                                        Procket Networks
                                                            October 2000


          Domain-wide Prefix Distribution with Two-Level IS-IS

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   This document describes extensions to the Intermediate System to
   Intermediate System (IS-IS) protocol to support optimal routing
   within a two-level domain.  The IS-IS protocol is specified in ISO
   10589, with extensions for supporting IPv4 (Internet Protocol)
   specified in RFC 1195 [2].

   This document extends the semantics presented in RFC 1195 so that a
   routing domain running with both level 1 and level 2 Intermediate
   Systems (IS) [routers] can distribute IP prefixes between level 1 and
   level 2 and vice versa.  This distribution requires certain
   restrictions to insure that persistent forwarding loops do not form.
   The goal of this domain-wide prefix distribution is to increase the
   granularity of the routing information within the domain.

1. Introduction

   An IS-IS routing domain (a.k.a., an autonomous system running IS-IS)
   can be partitioned into multiple level 1 (L1) areas, and a level 2
   (L2) connected subset of the topology that interconnects all of the
   L1 areas.  Within each L1 area, all routers exchange link state
   information.  L2 routers also exchange L2 link state information to
   compute routes between areas.






                             Informational