🚀 go-pugleaf

In article <16594@auspex-gw.auspex.com>, guy@Auspex.COM (Guy Harris) writes:
|> >The window is how much the other end is prepared to accept (65535 implies
|> >infinite). (this is bigger than the maximum packet size on every network
|> >I have ever seen)
|> 
|> Yes, but, as far as I know, it's not required that the sending TCP stuff
|> everything into one packet, and there's a "TCP Big Window" option
|> mentioned in RFC1106, to increase the maximum window size beyond 64K. 
|> 
|> There's also an RFC, RFC1110, entitled "A Problem with the TCP Big
|> Window Option"; both date back to mid-1989, and not being a full-time
|> networking weenie, I don't know what the state of Big Windows in TCP is
|> (except that I seem to remember Vernon Schryver talking about cranking
|> the window size up when using FDDI, in order to light the fibre up, so I
|> suspect there's at least a semi-stable standard for Big Windows).

RFC 1323 is the latest RFC describing big windows.  It is basically an
update to RFC's 1072 (window scaling, time-stamps for rtt measurement,
and selective acknowledgements) and 1185 (using the same time-stamps for
rejecting old, duplicate segments).  The selective acknowledgement was
dropped from 1323 because it was felt that more research needed to be
done.

RFC 1106 was another method of getting >64K windows.  I don't know much
about it.  The problem with big windows described in RFC 1110 (that a 32-bit
sequence number isn't good enough with 30-bit windows) was addressed in RFC
1185 and refined in RFC 1323.

RFC 1323 is pretty solid.  SGI's next major OS release will include a
TCP that can do RFC 1323 (both window scaling, and time-stamps).

Vernon nearly saturates an FDDI ring with a couple of Indigos and a single
TCP connection with a 60K window (no window scaling needed).  But, he likes
to crank up the window to 128K+ to squeeze the last 0.2 MBytes/s out.
Since the "big windows" will be available soon, you'll be able to try this
at home.


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Thomas Skibo         Advanced Networking, Silicon Graphics     skibo@sgi.com