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Re: Keynote/Boardwatch Results
From: "Alex.Bligh" <amb () xara net>
Date: Wed, 09 Jul 1997 22:12:09 +0100

 
SYN -> SYN/ACK time (actual connection)                       22%
Web browser says "Contacting www.website.com..."

SYN/ACK -> first data (web server work--              78%
getting material, processing material)
Web browser says "www.website.com contacted, waiting for response"

Note that this didn't include different types of content.  But it *did*
truly measure one thing--that the delay caused by web servers is
considerably higher than that of "network performance" (or actual connect
time).

Urm, maybe I'm missing something here, but taking an incredibly
simplistic model where you have a probability p of losing any packet,
there is a (1-p)^3 chance of 3 way handshake losing a packet and stalling,
and a (1-p)^(2 * no packets reqd for 1st data) for the latter. With
slow start etc there are bound to be more than two packets back before
it starts processing the response, so the latter is always going to
have a higher chance of failing. Now add to the fact that with technology
such as ATM, it is more likely large packets will be dropped than small
ones (with a given cell loss probability), and being careful to remember
all that good stuff at the last but one NANOG about broken client stacks,
and I think you might find the above is a "non measurement".

I *think* (and am not sure) that if you have a proxy set up, you
always get the latter once you have connected to the proxy.

Oh, and to skew the figures in the other direction, doesn't the first
prompt come up while the DNS lookup is being done?

Alex Bligh
Xara Networks





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