[ee122] Delayed ACK and CWND movement

Richard Schmidt huntingtonsurfca at gmail.com
Mon Nov 5 13:09:28 PST 2007

Doing the homework, TCP sends data ACK's every other packet it recieves.

When I was thinking about the CWND, I got confused as to how much this
would increase if the ACK's came only after every other packet (i.e.
half as many ACK's). I would think that the CWND would grow half as
fast as a result (since upon an ACK, CWND += MSS*(MSS/CWND)). But when
I was thinking about it rationally, the point of the previous equation
was to increment packets sent by 1MSS every RTT, and if this was
followed, then the ACK coming after about 2RTT's would let the CWND
increase at the same rate as if the ACK's came after every packet.

Can you please help clarify the equational relation and the rationale?


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