Route table growth and hardware to the filter

michael.dillon at michael.dillon at
Sun Sep 23 20:54:13 UTC 2007

> However, if they were transit-free, 
> they would, by definition, never have more than one peer for 
> any single-homed prefix.

And that sounds like a single point of failure to me. Let's look
at it another way by considering the path to any prefix. If there
is only one single path available, and a single event, such as the
depeering by one ASN, can lead to that path being broken, then you
have a network whose connectivity is not terribly robust.

If a network bites the bullet, and either openly buys transit, or
works out some partnership peering plus transit deal to hide the fact
that they have transit, then there is the possibility of having
two paths for every prefix. If they then take the trouble to analyze
the paths and adjust things to make sure that the multiple paths
to a single prefix don't share fate, then they stand a good chance
of having a robust network. 

The thinking, and the work involved, are a lot like what you need
to do in order to ensure physical separacy of fibre paths. It's the
same fundamental problem but perhaps more dynamic since circuits tend
to get groomed less often than paths change.

--Michael Dillon

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