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Re: GLBX ICMP rate limiting (was RE: Tier-1 without their own backbone?)
From: Paul Vixie <vixie () vix com>
Date: 28 Aug 2003 17:48:33 +0000


Along these lines, how does this limiting affect akamai or other 'ping
for distance' type localization services? I'd think their data would
get somewhat skewed, right?

using icmp to predict tcp performance has always been a silly idea; it
doesn't take any icmp rate limit policy changes to make it silly.  other
silly ways to try to predict tcp performance include aspath length
comparisons, stupid dns tricks, or geographic distance comparisons.

the only reliable way to know what tcp will do is execute it.  not just
the syn/synack as in some blast protocols i know of, but the whole session.
and the predictive value of the information you'll gain from this decays
rather quickly unless you have a lot of it for trending/aggregation.

"gee, ping was faster to A but tcp was faster to B, do you s'pose there
could be a satellite link, or a 9600 baud modem, in the system somewhere?"
-- 
Paul Vixie


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