filtering long prefixes

Michael Dillon michael at
Fri Sep 22 02:59:47 UTC 1995

On Thu, 21 Sep 1995, Sean Doran wrote:

> P.S.: This raises an interesting point that has been raised
> 	in private email to various folks concerned with
> 	206/8: if local aggregation cannot be done, then
> 	I suppose it would be easy enough to have some
> 	well-connected provider somewhere generate a prefix
> that is 18 bits long or shorter and deliver to the subnets 
> appropriately.  Whether this would be done out of the goodness
> of that provider's well-connected heart, or for a fee, is
> an interesting question.

Are you suggesting some sort of exchange point or NAP specifically to 
break out longer prefixes from shorter prefixes that cannot be 
topologically aggregated? Would something like this enable people
to maintain provider independent addressing (i.e. no renumbering) by 
merely paying a fee to an exchange point that is well connected and 
settling for less optimal routing?

If this will work in practice, it seems like the perfect tradeoff. On the 
one hand you must renumber when changing providers but you get optimal 
routing. On the other hand, you avoid renumbering but you pay a few bucks 
and have less than optimal routing.

Am I missing anything here?

Michael Dillon                                    Voice: +1-604-546-8022
Memra Software Inc.                                 Fax: +1-604-542-4130                             E-mail: michael at

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