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From John Heidemann <jo...@ISI.EDU>
Subject potential Apache performance problem: size of the TCP send buffer
Date Tue, 29 Oct 1996 02:06:07 GMT

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
<http://www.isi.edu/~johnh/SOFTWARE/APACHE/apache_1.1.1_isi_set_sndbuf.patch>
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 <http://www.isi.edu/~johnh/SOFTWARE/APACHE>.  For
descriptions of the problems motivating these patches, see
<http://www.isi.edu/lsam/publications/phttp_tcp_interactions/>.  [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




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