Re: Route Flap Damping: Harmful ?

["Christian Panigl, ACOnet/VIX/UniVie" <]

>Date: Wed, 18 Sep 2002 10:46:25 +0100
>From: Tony Barber acb@localhost
>
>I agree with you that RIPE should acknowledge its support for this research.
>I have a couple of observations to add before everyone agrees to go dropping 
>damping from their configurations:

    Thanks for your support Tony,
    
    of course, I was NOT suggesting to immediately obsolete RIPE-229 and to
    drop damping ;-)

>1) Its hard to dispute that NO damping is better than the suppression of
>constantly oscilating routes from my perspective, as a steady state *will*
>always be reached.  As Randy states, it may require less aggressive
>parameters to achieve this.

    Remember when we started to draft the first version (RIPE-178), the goal
    was to get rid of exaggeratedly aggressive damping which was at that
    time applied by some major US carriers.  I always was standing for a
    very "flat and gentle" damping approach but for the sake of getting the
    aggressive guys playing along we then compromised to "graded damping".

>How important is it in this context to still have damping in place ?

    I'm inviting you to look at
    
    http://www.aco.net/lookingglass/lg.html [flap statistics]
    
    at that router (Cisco) we have configured flap damping according to
    RIPE-229 and we are receiving a full and undamped routing table through
    GEANT and GlobalCrossing (^20965_3549_).  You can clearly see that
    something very weird is going on "somewhere".
    
    Looking at those flap statistics raises the question how much "less
    aggressive" the parameters should be :-(
    
    I don't think damping is still essential for the stability of todays core
    routers, but it obviously would be essential to improve the stability at
    some spots of the Internet and to improve convergence, either with a new
    version of BGP or a completely new inter-domain routing protocol.
    
    Kind regards
    CP