[e2e] TCP un-friendly congestion control

[Guglielmo Morandin]

Craig, you will take 18 rtt if the cwnd doubles every rtt.
But after a packet drop the congestion window is supposed to grow by 
just one packet every rtt, isn't it?

BTW, even slow start is not really doubling the window every rtt, if you 
take into consideration delayed acks.

-Guglielmo


Craig Partridge wrote:
> In message <000001c32c54$43ec4ae0$9d350e98 at HD>, "Injong Rhee" writes:
> 
> 
>>My definition for fast, long distance networks might have been perhaps
>>too liberal. In case of 1Gbps and 50ms, its B x D is 4167 packets
>>assuming 1500 byte packets. It will take around 2083 (4167 after worst
>>case timeout) round trip times which is around 104 (208) seconds. If the
>>delay increases to 100ms and 200ms, this becomes 6 min and 28 min. As
>>you scale the bandwidth to 10G, this becomes ...well..I guess that
>>should be enough. 
> 
> 
> I don't understand your logic here.
> 
> The bandwidth*delay product is indeed around 6,250,000 bytes which is
> 4167 segments.
> 
> The maximum TCP window size is 2^30 which is 1,073,741,824 or at least
> two orders of magnitude larger than required.
> 
> The number of round-trips required to reach this window size is approximately
> 18 RTTs, which is 0.9 seconds.
> 
> So... I don't see where 2083 RTTs comes from, nor 6 or 28 minutes.
> 
> Craig
>