<?xml version='1.0'?>

<reference anchor='RFC2439'>

<front>
<title>BGP Route Flap Damping</title>
<author initials='C.' surname='Villamizar' fullname='Curtis Villamizar'>
<organization>ANS</organization>
<address>
<email>curtis@ans.net</email></address></author>
<author initials='R.' surname='Chandra' fullname='Ravi Chandra'>
<organization>Cisco Systems</organization>
<address>
<email>rchandra@cisco.com</email></address></author>
<author initials='R.' surname='Govindan' fullname='Ramesh Govindan'>
<organization>ISI</organization>
<address>
<email>govindan@isi.edu</email></address></author>
<date month='November' year='1998' />
<area>Routing</area>
<keyword>border gateway protocol</keyword>
<keyword>BGP</keyword>
<keyword>routing</keyword>
<abstract>
<t>
   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.
</t>
<t>
   The overall goals are:

<list>
<t>
   o  to provide a mechanism capable of reducing router processing load
      caused by instability
</t>
<t>
   o  in doing so prevent sustained routing oscillations
</t>
<t>
   o  to do so without sacrificing route convergence time for generally
      well behaved routes.
</t></list></t>
<t>
   This must be accomplished keeping other goals of BGP in mind:

<list>
<t>
   o  pack changes into a small number of updates
</t>
<t>
   o  preserve consistent routing
</t>
<t>
   o  minimal addition space and computational overhead
</t></list></t>
<t>
   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
   &quot;route flap&quot;.  The techniques described here are now widely deployed
   and are commonly referred to as &quot;route flap damping&quot;.
</t></abstract></front>

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