RFC 1998 (rfc1998) - Page 1 of 9

An Application of the BGP Community Attribute in Multi-home Routing

Network Working Group                                            E. Chen
Request for Comments: 1998                                           MCI
Category: Informational                                         T. Bates
                                                           cisco Systems
                                                             August 1996


             An Application of the BGP Community Attribute
                         in Multi-home Routing


Status of This Memo

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

Abstract

   This document presents an application of the BGP community attribute
   [2] in simplifying the implementation and configuration of routing
   policies in the multi-provider Internet. It shows how the community
   based configuration can be used to replace the AS-based customization
   of the BGP "LOCAL_PREF" attribute, a common method used today.  Not
   only does the technique presented simplifies configuration and
   management at the provider level, it also represents a paradigm shift
   in that it gives the potential for the customer to control its own
   routing policy with respect to its service provider, as well as
   providing the ability for policy configuration to be done at a prefix
   based granularity rather than the more common AS based granularity.

1. Introduction

   In the multi-provider Internet, it is common for a service subscriber
   (i.e., customer) to have more than one service provider, or to have
   arrangements for redundant connectivity to the global connected
   Internet. As discussed in [3], routing strategies in these cases
   usually require coordination between the service subscriber and its
   providers, which typically leads to customization of router
   configurations (e.g., BGP "LOCAL_PREF") not only by the subscriber,
   but also by its providers.  Due to the large number of customers a
   provider serves, customization of router configurations at the
   provider level may present management and scalability problems.

   This document presents an application of the BGP community attribute
   in simplifying the implementation of routing strategies in the
   multi-provider Internet.  More specifically, the technique presented
   uses a community-based, rather than the common AS-based,



Chen & Bates                 Informational