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Re: "Selfish Routing"
From: Sean Finn <seanf () routescience com>
Date: Fri, 14 Feb 2003 17:51:18 -0800



Abstractions and analogies aside, is this really a problem,
and is it really worth solving? Sounds like a lot of
additional complexity for the supposed benefits.


A key comment to put this paper in perspective:
(from http://news.com.com/2100-1033-984694.html?tag=fd_top )
> "The extent to which the real Internet conforms to these
> mathematical models is not yet well understood," Roughgarden
> said.

In particular, BGP does uses neither latency not congestion as
a parameter to choose a path. (assuming that conditions are such
that the BGP session can stay up, of course ;).

Widespread deployment of a pure-performance criteria for path
selection could indeed have the type of problem described. Standard
BGP flap dampening mechanisms would mitigate, but not eliminate,
the potentially negative effects described.

Chasing the last ms of optimization tends to both focus traffic
on the single "best" link, as well as increasing the rate of route
change as the "best" continually changes.

Considering alternate paths with roughly similar performance
significantly changes the picture. This not only reduces the
required rate of route change, but also tends to spread the
load across the range of valid (near-optimal) paths, and thus
significantly mitigates the concerns raised in the paper.

cheers -- Sean



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