North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Aggressive route flap dampening
[email protected] (Sean M. Doran) writes: > The "N" should be reduced (or the time period lengthened) and the > cost of increasing that ratio should increase with the length of > the prefix, in order to encourage topologically sound aggregation > either through traditional means or through NAT and NAT-like boxes > such as the one described and implemented by Paul Vixie. Here's where we part company. Varying the 'charge', either monetary or in flap penalty creates an incorrect incentive: folks are incented to use a shorter prefix. Note that this is distinct from aggregation in that they may simply use a shorter prefix and not actually use more address space, thus hurting netwide utilization. The 'correct' incentive is a charge for flapping and a charge for announcement. Both have real costs, directly traceable to processor and memory costs. > It fixed two problems simultaneously: firstly, there is lots of flap > and flap is most irritating when relatively unimportant (and statistically > small is likely to be less important than large) NLRI is responsible for > a disproportionally large amount of it. Secondly, there are lots of > networks which really ought to be aggregated. When a single up/down or > up/down/up flap makes the network unusable for an hour or two, people > generally become motivated either to be very very stable or to aggregate > even adjacent aggregatable /24s in order to suffer fewer disconnectivities. Note that both of these are 'fixed' without a length restriction: the per prefix charge incents folks to aggregate. The per flap charge incents them to stability. Direct cause and effect, without harmful side effects. ;-) Tony
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