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

Detlef Bosau detlef.bosau at web.de
Wed Jan 3 03:13:10 PST 2007

Lachlan Andrew wrote:
> Greetings,
> On 02/01/07, Joe Touch <touch at isi.edu> wrote:
>> Detlef Bosau wrote:
>> > Round    CWND
>> >    1              2
>> >    2              4
>> >    3              8
>> It doesn't double each RTT; it goes up by 50%. Remember, the window
>> grows by one MSS each ACK during the initial phase, but there is one ACK
>> for each two MSS's.
> If you have ABC (as recent Linux senders do by default), or don't use
> delayed ACKs (as Linux receivers don't when the window is small),
> Detlef was right that it doubles each RTT.
> $0.02
> Lachlan

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.

 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.

I´m talking too much. Please forgive me, if I miss to mention all my 
assumptions ...


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