[e2e] Are we doing sliding window in the Internet?
detlef.bosau at web.de
Sun Dec 31 11:15:44 PST 2006
Happy New Year, Miss Sophy My Dear!
(Although this sketch is in Englisch, it is hardly known outside Germay
to my knowledge.)
I wonder whether we´re really doing sliding window in TCP connections
all the time or whether a number of connections have congestion windows
of only one segment, i.e. behave like stop´n wait in reality.
When I assume an Ethernet like MTU, i.e. 1500 byte = 12000 bit, and 10
ms RTT the throughput is roughly 12000 bit / 10 ms = 1.2 Mbps.
From this I would expect that in quite a few cases a TCP connection
will have a congestion window of 1 MSS or even less.
In addition, some weeks ago I read a paper, I don´t remember were, that
we should reconsider and perhaps resize our MTUs to larger values for
networks with large bandwidth. The rationale was simply as follows: The
MTU size is always a tradeoff between overhead and jitter. From Ethernet
we know that we can accept a maximum packet duration of 12000 bit / (10
Mbps) = 1.2 ms and the resultig jitter. For Gigabit Ethernet
a maximum packet duration of 1.2 ms would result in a MTU size of 1500
kbyte = 1.5 Mbyte.
If so, we would see "stop´n wait like" connections much more frequently
Is this view correct?
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