On 23-nov-04, at 11:09, Elmar K. Bins wrote:
Well, suppose we know 212/8 is used in Europe. A network that is present in say, North America and Europe then has the routers in Europe that talk to the routers in America filter out all 212/8 more specifics and only announce the aggregate instead. In the simple version this only works if there is full interconnection for all 212/8 destination in Europe.
And if everyone gives transit to anyone. Ideal world.
Actually everyone giving everyone transit is far from ideal. We've seen this happen in IPv6, with poor performance as a result. The trouble is that the destination of the traffic can do very little to improve this even if good connectivity is also present. But that's not what I'm saying anyway. If aggregates are only used within ASes and not communicated to other ASes, the macro view will stay the same. We just remove information in places where it has no added value. For example, someone in Los Angeles really doesn't care whether a packet goes to Darmstadt or Hannover. All they care about is that the packets move to the east. The correlation between network topology and geography doesn't have to be perfect. The number of routing table entries saved corresponds to the level of topology/geo correlation. Anything from 50% and up would be worthwhile, IMO.