[e2e] TCP un-friendly congestion control

[Craig Partridge]

In message <4CA02219-9918-11D7-AEC6-003065DC1D5E at cisco.com>, Guglielmo Morandin
 writes:

>> So run that logic.  Suppose the available capacity is 1 Gbps (and if
>> it isn't, why are we having this discussion?) and so around the point
>> we hit 1 Gbps we regularly get a congestion loss.
>>
>Isn't your assumption a little too strict to be useful in reality? If I 
>do have guaranteed
>1Gbps capacity, I don't need tcp. I could just shape my flow at a rate 
>slightly
>lower, and retransmit packets that are dropped because of bit errors.

Well, run that logic.  If you have 1 Gbps guaranteed, you can set your
TCP window to the right size and run congestion loss free too....

I agree that one has to look very carefully at BER (though remember that
bit errors are not evenly distributed -- what you're likely to see is
a situation where, say, 90% of connections never see a bit error and 10%
do).

>I doubt that 750Mbps can be sustained by standard tcp in a real 
>network, unless available capacity is much bigger.
>But bandwidth is not THAT cheap.

TCP running at 700+Mbps over real networks was demonstrated by Cray over 
a dozen years ago.

Craig