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Re: [RRG] Geographic aggregation-based routing
On 16 jul 2008, at 17:41, William Herrin wrote:
You more or less re-propose provider-aggregatable addressing with
geographic registries, an approach which has been in place for better
than a decade now and has already achieved the close to the maximum
aggregation it can.
You mean that PA has already gone as far as it can go and geoPI == PA?
Not so. The big difference is that with geoPI you get to switch ISPs
without changing your address. (Including connecting to more than one
ISP at the same time.) This is exactly the thing that PA won't give you.
I personally think there's still a little room for improvement in the
FIB calculation. It might be possible to reduce the FIB by selecting
the most-common exit in the RIB for each /8 and then only installing
the more specifics in the FIB for the prefixes that use a different
exit. But the closer you get to the core, the less improvement that
offers, something you should be able to confirm or refute with RIB
snapshots from various operators if you care to try it.
That's because today, there is little rhyme or reason to the
distribution of prefixes within each of those /8s. However, if you
know that everything in 145.0.0.0/8 is in the Netherlands, there is
really no reason to keep all those more specifics in your routers in
Seattle, as interconnection with Dutch networks typically happens in
Amsterdam with backups in England and Germany, or at the very least in
the US north east, where all the transatlantic cables land.
Since there is no cost (except for updating some registry machinery)
for doing geoPI rather than straight PI for IPv6, there's really no
reason NOT to do it.
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