Re: Powers-of-two - 7 for recv() length??
From: Stephen Hemminger
Date: Wed Mar 31 2004 - 13:53:58 EST
On Wed, 31 Mar 2004 13:02:03 -0500 (EST)
"Richard B. Johnson" <root@xxxxxxxxxxxxxxxxxx> wrote:
> On Wed, 31 Mar 2004, Stephen Hemminger wrote:
> > What is the socket send/receive buffering, and the underlying network.
> > You need to look at the data flow with something like tcpdump and tcptrace.
> > If you get flow controlled or lots of other reasons, TCP will validly
> > send a small number of bytes (like 1) which will get things out of alignment.
> Hmmm. I get lots of truncated IP packets. See attached. I've tried
> to help by setting both RCV_BUF and SND_BUF to 1/2 megabytes. Nothing
> seems to work except sending only 1436 bytes at a time. That makes
> everything miserably slow. 1436 comes from (1500 - 64) 1500 being the
> ethernet packet length, 64 being the IP header length.
That is because you are running on the loopback interface that has an
MTU of 16K. And tcpdump is being smart and only reading part of the
> Dick Johnson
> Penguin : Linux version 2.4.24 on an i686 machine (797.90 BogoMips).
> Note 96.31% of all statistics are fiction.
Stephen Hemminger mailto:shemminger@xxxxxxxx
Open Source Development Lab http://developer.osdl.org/shemminger
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