RFC 2918 (rfc2918) - Page 1 of 4

Route Refresh Capability for BGP-4

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Network Working Group                                            E. Chen
Request for Comments: 2918                              Redback Networks
Category: Standards Track                                 September 2000


                   Route Refresh Capability for BGP-4

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 Internet Society (2000).  All Rights Reserved.

Abstract

   This document defines a new Border Gateway Protocol (BGP) capability
   termed 'Route Refresh Capability', which would allow the dynamic
   exchange of route refresh request between BGP speakers and subsequent
   re-advertisement of the respective Adj-RIB-Out.  One possible
   application of this capability is to facilitate non-disruptive
   routing policy changes.

1. Introduction

   Currently there does not exist a mechanism in BGP-4 [BGP-4] to
   dynamically request a re-advertisement of the Adj-RIB-Out from a BGP
   peer.  When the inbound routing policy for a peer changes, all
   prefixes from that peer must be somehow made available and then re-
   examined against the new policy. To accomplish this, a commonly used
   approach, known as 'soft-reconfiguration', is to store an unmodified
   copy of all routes from that peer at all times, even though routing
   policies do not change frequently (typically no more than a couple
   times a day). Additional memory and CPU are required to maintain
   these routes.

   This document proposes an alternative solution that avoids the
   additional maintenance cost. More specifically, it defines a new BGP
   capability termed 'Route Refresh Capability', which would allow the
   dynamic exchange of route refresh request between BGP speakers and
   subsequent re-advertisement of the respective Adj-RIB-Out.





Chen                        Standards Track
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