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Re: [RRG] Geographic aggregation-based routing
On 13 jul 2008, at 22:53, William Herrin wrote:
Hence we have found a contradiction: a valid network configuration for
which your algorithm can't meet the constraints. If this was math,
we'd say it was disproven. Since it's engineering, we say something
along the lines of: disqualified for technical error.
It turns out that -all- geographic aggregation strategies suffer from
a variant of this problem. That's why none of the rest of us are
interested in talking about geographic aggregation.
You're oversimplifying.
If you split the world into regions and then have interconnections
between different networks in some regions but not in all of them, you
can't solve routing if you first send packets to the target region and
then try to hand them over to the target network.
(Note that you can easily reverse this problem: today we route to the
target network and then to the target region. This works with
incomplete regional interconnection between networks, but it fails if
different parts of a single network become partitioned. Hence we spend
a lot of money and effort to make sure that doesn't happen.)
The solution is rather than to impose 100% geographical aggregation,
just apply the aggregation when the more specific and the aggregate
align. If they don't, keep the more specific. This way, we get to
benefit from the regionality that is clearly present in the network,
especially outside huge countries like the US and (presumably) China,
while at the same time not imposing any new requirements on protocols
or business models.
However, we DO need to start giving out addresses in a geographically
aggregatable way, rather than in pseudo-random fashion, the way things
happen today. There is no guarantee this will help, but at least there
is the possibility of future geographic aggregation, while if this
doesn't materialize we're no worse of than today. The way things are
now we KNOW there is no way to aggregate PI prefixes.
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