Re: about Area Splitting

[Tony Przygienda <[e-mail]>]

Li, Ke Qin (Peter) wrote:

>Hi,
>
>        I've read the Internet Draft "OSPF Areas Considered Harmful" written
>by Mikkel Thorup
>http://www.ietf.org/internet-drafts/draft-thorup-ospf-harmful-00.txt. In
>Section 8.0 "Summarization and infinite loops", a scenario is described
>where area splitting results in infinite routing loop (although IMHO it is
>black hole). I think it is a basic problem related to OSPF hierarchy and
>area range. Has this problem been discussed in this list before? If yes,
>what is the solution?
>
>        Thank you very much!
>
>Keqin Li
>Bell Labs Research China
>Tel: [phone]-8438
>
>
>
I discussed and started to write once with John what we considered the
optimal solution (and I know some people
implemented it). Basically, when you realized that you see through the
backbone advertisement of an ABR in your
area that you
don't have intra-area connectivity to, you inject with the summary all
the more specifics into the backbone. Simple
to implement, the only real disadvantage really being that you may put
tons of routes into the backbone. On the other
hand, you're only real other solutions are either for one to stop
advertising (avg. 50% of area goes down) or
maybe have some complicated 'tunnel-through-backbone' solution, which we
didn't think was worth the effort.

If anybody feels like writing that down, I can help a bit, I don't think
I will find my writedown anymore on all my
harddisks lying around ; -)

-- tony