[76774] in North American Network Operators' Group
Re: Dampening considered harmful?
daemon@ATHENA.MIT.EDU (Mark Kent)
Mon Dec 27 21:16:57 2004
Date: Mon, 27 Dec 2004 18:16:24 -0800 (PST)
From: Mark Kent <mark@noc.mainstreet.net>
To: nanog@nanog.org
Errors-To: owner-nanog-outgoing@merit.edu
Back in mid-December someone typed:
> > One reason to be careful with dampening is that flaps can be
> > multiplied. (Connect to routeviews and see the different flap counts
> > under different peers for the same flap at your end to observe this.)
How about in this scenario:
asA gets transit from asT
asA gets backup transit (ASpath padding) from asB
asB gets transit from asT
asB gets transit from asJ
asJ gets transit from asT
asT peers with whole world(*)
Now, as asA flaps to asT, we see "bad things" happen to their routes,
namely an unreasonable amount of flap at even nearest neighbors to asT.
Can this flap magnification be explained by the hierarchy I describe
above? That is, asT treats all of these ASpaths as customer routes:
asA
asB_asA
asJ_asB_asA
and so we might expect to see multiple flaps as different "best"
routes come into view inside the geographically diverse asT... right?
Thanks,
-mark
(*)you know what I mean.
