Re: tcp on SUN computers.


Bill Nowicki (nowicki%rose@SUN.COM)
Tue, 10 Jun 86 11:51:02 PDT


        I have found that with Sun release 2.0 "the world will break"
        if I patch tcp_sendspace and tcp_recvspace to be only 16K, not
        32K. At 15K it works, but 16K crashes.

Please clarify what you mean by "world will break". Last week I did
some tests and tried various sizes like 16K and 32K without any
"crashes". There is a severe performance problem if one side has a
large recvspace and the other has a sendspace that is less than or
equal to one quarter of the recvspace. The "silly window syndrome
avoidance feature" then takes effect, and you can send only five times
the sendspace per second. For example, if a machine with increased
recvspace (8K) sends to a machine with the default sendspace of 2K,
then throghput is 10Kbytes/second, about twenty times slower than 2K
sending to 2K! This is probably true for 4.2 in general, but have
not tried the 4.3BSD SWSA code.

Note that my experiments are using Sun-3s running 3.x -- you should
upgrade from 2.x as soon as you can, since 3.x has several of the 4.2BSD
bugs removed.

        -- Bill Nowicki
           Sun Micsrosystems



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