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From Rob Hartill <>
Subject Re: potential Apache performance problem: size of the TCP send buffer
Date Tue, 29 Oct 1996 08:04:55 GMT

Thanks John for the info/pointers/patch. I'll pass this on to the developers
list for consideration.


John Heidemann wrote:
>Apache-1.1.1 doesn't appear to set the size of the TCP send buffer.
>On many systems the default send-buffer size is too small to support
>full-rate transfer over high bandwidth-delay-product networks (such as
>cross-US Internet traffic).  For example, a 100ms round-trip time
>(typical cross-US latency) and a 4kB default buffer size (common to
>many OSes such as SunOS) limit transfer rate to 40kB/s.
>Much better cross-US transfer rates are possible between
>well-connected hosts if the send buffer size is increased.  A patch at
>implements the SendBufferSize directive to allow Apache to have a
>configurable buffer size.
>A complete description of this directive is in the file
>send_buffer_size.html which accompanies the patch.  For a pointer to
>other patches, see <>.  For
>descriptions of the problems motivating these patches, see
><>.  [For
>those of you who have seen this web page before, there are some new
>figures in ``The Performance Problems'' section and the buffer-size
>problem is described under ``Other Problems'' there.]
>   -John Heidemann
>    USC/ISI

Rob Hartill (  ... why wait for a clear night to see the stars?.

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