[e2e] TCP un-friendly congestion control

[Craig Partridge]

In message <3EE0E340.4030102 at cisco.com>, Guglielmo Morandin writes:

>Craig, you will take 18 rtt if the cwnd doubles every rtt.

Actually, if it grows by 50% each RTT.

>But after a packet drop the congestion window is supposed to grow by 
>just one packet every rtt, isn't it?

Only after hitting half the congestion window.

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.

CWND runs at 500 Mbps and it takes only a few RTTs to grow to that
size.

After CWND (at which times we're at 500 Mbps) we grow linearly to 1 Gbps.

That says our average data rate is just under 750Mbps for a 1 Gbps link.
(Assuming no error loss -- which starts to become a factor on some
channels at these rates).

Craig