Re: SYN floods continue

[Vern Paxson <vern () ee lbl gov>]

> That prohibits IP src spoofing (and asymmetrical paths).
> ...
> In most networks asymmetrical routing is an indication of a bug in
> an IGP configuration, so early detection of the configuration problems
> would be an additional benefit.

In my Internet end-to-end routing study I found that fully 50% of the pairs
of paths through the Internet had a major asymmetry at the end of 1995.
"Major" meaning: visited at least one different city in the two directions.
(30% visited at least one different AS.)  This was a significant increase
over the same figure for the end of 1994, 30%.  So it may be quite hard to
make and keep Internet routing symmetric.

The paper's available from:

        ftp://ftp.ee.lbl.gov/papers/routing.SIGCOMM.ps.Z

- Vern
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