smd@clock.org (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