The Big Squeeze

Sean Donelan SEAN at SDG.DRA.COM
Mon Mar 3 04:23:33 UTC 1997

>> I would suggest that the largest percentage of flapping prefixes in the
>> global routing system belong to prefixes longer than /19.
>Hence the convention to damp differently for different lengths.  See one of
>the foils in, which suggests that we
>over here start following the European lead on this.

Is the route computation of a /8 prefix flapping once a second any
different than a /24 flapping once a second?  If /8's are "naturally"
more stable, then why allow them to flap more before dampening them?

When dampening was first being rolled out I remember one of the early
networks that got hit was PSI's net 38/8.  Treating flapping prefixes
differently based on length has more to do with how many people scream
when prefixes covering a large amount of address space get dampened
than the impact of the route flap of an individual prefix on the router.

Although most folks have permanently filtered it, isn't 1/8 still the
flappiest prefix of all.
Sean Donelan, Data Research Associates, Inc, St. Louis, MO
  Affiliation given for identification not representation

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