[e2e] Are we doing sliding window in the Internet?

Joe Touch touch at ISI.EDU
Wed Jan 3 08:20:27 PST 2007

Detlef Bosau wrote:
> Just before I´m to end my life on "Yellow Mama" .......  ;-)
> I admit that I often forget to mention all my assumptions. And even
> more, I don´t have all the RFCs in mind, particularly not rfc 3390,
> which Joe has in mind when he talks of an initial window of 4 MSS.
> When I do NS2 simulations, I mostly turn off delayed ACKs for my
> purposes at the moment.
> From the congavoid paper, I understand that the intention was to double
> CWND each round if the sender is in slow start state and to increase it
> by 1 MSS each round when the sender is in congestion avoidance state.

The original intention was to double it, but since delayed ACKs that
hasn't been the case. The current AI is 1.5x in slowstart, and has been
for quite a long time.

> From my understanding it is not necessary for the AIMD scheme to work
> that this doubling/increasing happens every or every other round.
> Of course, it affects the convergence time.

It also affects fairness when different connections use different
factors, either for AI or MD.


Joe Touch
Sr. Network Engineer, USAF TSAT Space Segment

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