[56473] in North American Network Operators' Group
Re: 923Mbits/s across the ocean
daemon@ATHENA.MIT.EDU (David G. Andersen)
Sun Mar 9 13:00:48 2003
Date: Sun, 9 Mar 2003 12:59:55 -0500
From: "David G. Andersen" <dga@lcs.mit.edu>
To: Iljitsch van Beijnum <iljitsch@muada.com>
Cc: Joe St Sauver <JOE@OREGON.UOREGON.EDU>, nanog@nanog.org
In-Reply-To: <20030309140553.L58283-100000@sequoia.muada.com>
Errors-To: owner-nanog-outgoing@merit.edu
On Sun, Mar 09, 2003 at 02:25:25PM +0100, Iljitsch van Beijnum quacked:
>
> On Sat, 8 Mar 2003, Joe St Sauver wrote:
>
> > you will see that for bulk TCP flows, the median throughput is still only
> > 2.3Mbps. 95th%-ile is only ~9Mbps. That's really not all that great,
> > throughput wise, IMHO.
>
> Strange. Why is that? RFC 1323 is widely implemented, although not
> widely enabled (and for good reason: the timestamp option kills header
> compression so it's bad for lower-bandwidth connections). My guess is
> that the OS can't afford to throw around MB+ size buffers for every TCP
> session so the default buffers (which limit the windows that can be
> used) are relatively small and application programmers don't override
> the default.
Which makes it doubly a shame that the adaptive buffer tuning
tricks haven't made it into production systems yet. It was
a beautiful, simple idea that worked very well for adapting to
long fat networks:
http://www.acm.org/sigcomm/sigcomm98/tp/abs_26.html
-dave
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