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Re: BSD doesn't track window size changes correctly.

On 3 Apr, 2012, at 11:21 , David Laight wrote:

> From experiments I've done with other protocols, it is certainly
> best not to reduce the window to zero - because missing the window
> opening msg is problematical. Best to leave it open a bit and
> defer sending acks. (might confuse RTT timings though!)

You probably won't find it in any specification document but the
routing protocol BGP depends quite strongly on zero-window TCP being
well-working for stability.  In fact it could be argued that BGP
came to be used for almost all the heavy lifting of Internet routing
for a couple of decades now precisely because of this feature of the
TCP transport.  Prior routing protocols had custom transports with no
equivalent to a zero window to shut your neighbors up, and as a result
were inherently difficult to keep from melting if you carried a lot of
routes in there and then put the routers under stress (networks running
BGP have been known to melt as well, but generally from bad implementations
rather than difficulties inherent in the design).

I don't usually pay much attention to TCP, but I cringe a bit when I hear
about problems with zero window behavior.

Dennis Ferguson

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