[e2e] Unexpected small reduction in cwnd during iperf test

Xiaoliang (David) Wei weixl at caltech.edu
Wed Aug 9 03:35:17 PDT 2006

Thanks, Toby.

>> as the cwnd before this glitch has been kept to 5931 unchanged for
>> several RTTs (I assume the RTT in your case is in the order of 100ms
>> across the Atlantic), I guess one possibility is that there is some ack
>> packet reordering.
> It is certainly possible (almost likely) that ACKs are being reordered,
> but I hadn't realised that would have any knock on effect - I'd always
> thought that a disordered 'late' ACK would be ignored as the disordered
> 'early' ACK would have acknowledged its sequence space.

I think you are right... I was thinking the reordering of data packets. (But 
on the other hand, as SACK is enabled, the number of packets in flight 
should not decrease in the event of data packet reordering).


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