Dear RIPE Routing-WG members, at the RIPE43 meeting in Rhodes last week Randy Bush was giving an interesting presentation on recent observations of counterproductive effects of current implementations of BGP Route Flap Damp(en)ing. The presentation is available in Acrobat Reader format at: http://www.ripe.net/ripe/meetings/archive/ripe-43/presentations/ripe43-routi... Brief summary: Basically because of "Cascaded Withdrawals" a single original flap of a prefix may cause the route flap penalty to exceed the suppress threshold at some points (routers) in the Internet. Main reasons for this behaviour are the characteristics of BGP (path vector), variations in BGP timers and delays, algorythm, implementation and parameters of current Route Flap Damping. This phenomenon is also (though less clearly) described in RIPE-229 (Flap Damping Parameter Recommendation), as it was in its predecessors since early 1998: http://www.ripe.net/ripe/docs/ripe-229.html#4.1 Only in late July this year I did again observe severe occurences of this phenomenon and was starting a conversation with Philip Smith (Cisco) and others. Now there is a SIGCOM 2002 Publication (August 2002) "Route Flap Damping Exacerbates Internet Routing Convergence" by Z.Mao and others: http://www.cs.berkeley.edu/~zmao/Papers/sig02.pdf I would like to thank the authors for the excellent research and, as one of the authors of RIPE-229 and its predecessors, I'm acknowledging that we haven't yet been able to analyse this specific problem in detail, but have communicated it to e.g. the MERIT/IPMA project team. I'm therefore more than grateful that Z.Mao and his co-authors did finally investigate it and would like to propose to the RIPE Routing-WG that we formally acknowledge their work, and specifically support their conclusion. Comments are of course welcome ! Kind regards CP --- ---------------------------------------------------------------------- --- --- Christian Panigl : Vienna University Computer Center - ACOnet --- --- VUCC - ACOnet - VIX : -------------------------------------------- --- --- Universitaetsstrasse 7 : Mail: Panigl@CC.UniVie.ac.at (CP8-RIPE) --- --- A-1010 Vienna / Austria : Tel: +43 1 4277-14032 (Fax: -9140) --- --- ---------------------------------------------------------------------- ---