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SubjectRe: More TCP speed fixes
According to Eric Schenk:
> (5) I've made some changes to the way delayed ACKs are treated.
> In particular if the packet interarrival time is larger than
> 1/2 second, then delaying ACKs is a bad idea, since it will just
> result in skewing the RTT calculation for the sender.
> So, I changed things so that if sk->ato > HZ/2, we simply don't
> delay the ACK at all.

Note that when you implement such fixed time comparisons, you may
adversely affect performance in environments that are operating slower
than you think is reasonable.
Most notably, amateur packet radio (which benefits a lot from any delayed
ack scheme) often has packet interarrival times > 1/2 second.

It is better to adjust the time threshold depending on the serial speed
and the MTU or MRU.
(of course, as I wrote earlier, performance in amateur packet radio
will benefit even more from a TCP implementation that knows about
halfduplex interfaces and does not queue replies before carrier drops)


| Rob Janssen | BBS: +31-302870036 (2300-0730 local) |

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