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Re: "Does TCP Need an Overhaul?" (internetevolution, via slashdot)
On Apr 5, 2008, at 9:40 AM, Kevin Day wrote:
That's only partially correct: TCP doesn't _time out_, but it still cuts its sending window in half (ergo, it cuts the rate at which it sends in half). The TCP sending rate computations are unchanged by either NewReno or SACK; the difference is that NR and SACK are much more efficient at getting back on their feet after the loss and:
a) Are less likely to retransmit packets they've already sent
b) Are less likely to go into a huge timeout and therefore back to slow-start
You can force TCP into basically whatever sending rate you want by dropping the right packets.
are downloading you're either throwing away data from the server (which is wasting bandwidth getting all the way to you) or throwing away your clients' ACKs. Lost ACKs do almost nothing to slow down TCP unless you've thrown them *all* away.
You're definitely tossing useful data. One can argue that you're going to do that anyway at the bottleneck link, but I'm not sure I've had enough espresso to make that argument yet. :)
I'm not saying all of this is completely useless, but it's relying a lot on the fact that the people you're trying to rate limit are going to be playing by the same rules you intended. This makes me really wish that something like ECN had taken off - any router between the two end-points can say "slow this connection down" and (if both ends are playing by the rules) they do so without wasting time on retransmits.