BGP Route Flap Damping (RFC2439)
Original Publication Date: 1998-Nov-01
Included in the Prior Art Database: 2019-Feb-11
Internet Society Requests For Comment (RFCs)
C. Villamizar: AUTHOR [+2]
A usage of the BGP routing protocol is described which is capable of reducing the routing traffic passed on to routing peers and therefore the load on these peers without adversely affecting route convergence time for relatively stable routes. [STANDARDS-TRACK]
Network Working Group C. Villamizar Request for Comments: 2439 ANS Category: Standards Track R. Chandra Cisco R. Govindan ISI November 1998
BGP Route Flap Damping
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 (C) The Internet Society (1998). All Rights Reserved.
A usage of the BGP routing protocol is described which is capable of reducing the routing traffic passed on to routing peers and therefore the load on these peers without adversely affecting route convergence time for relatively stable routes. This technique has been implemented in commercial products supporting BGP. The technique is also applicable to IDRP.
The overall goals are:
o to provide a mechanism capable of reducing router processing load caused by instability
o in doing so prevent sustained routing oscillations
o to do so without sacrificing route convergence time for generally well behaved routes.
This must be accomplished keeping other goals of BGP in mind:
o pack changes into a small number of updates
o preserve consistent routing
Villamizar, et. al. Standards Track [Page 1]
RFC 2439 BGP Route Flap Damping November 1998
o minimal addition space and computational overhead
An excessive rate of update to the advertised reachability of a subset of Internet prefixes has been widespread in the Internet. This observation was made in the early 1990s by many people involved in Internet operations and remains the case. These excessive updates are not necessarily periodic so route oscillation would be a misleading term. The informal term used to describe this effect is "route flap". The techniques described here are now widely deployed and are commonly referred to as "route flap damping".
To maintain scalability of a routed internet, it is necessary to reduce the amount of change in routing state propagated by BGP in order to limit processing requirements. The primary contributors of processing load resulting from BGP updates are the BGP decision process and adding and removing forwarding entries.
Consider the following example. A widely deployed BGP implementation may tend to fail due to high routing update volume. For example, it may be unable to maintain it’s BGP or IGP sessions if sufficiently loaded. The failure of one router can further contribute to the load on other routers. This additional load may cause failures in other instances of the same implementation or other implementations with a similar weakness. In the worst case, a stable oscillation could result. Such worse cases have already been observed in practice.
A BGP implementation must be prepared for a large volume of routing traffic. A BGP implementation cannot rely...