Messages in this thread | | | Date | Tue, 16 Nov 1999 13:31:18 -0500 (EST) | From | "Mike A. Harris" <> | Subject | Re: Skyhigh retransmit times. Yearold problem still in 2.3.26 |
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On Sun, 14 Nov 1999, Steve Underwood wrote:
>> > >> > netstat -ton >> > >> > tcp 0 0 127.0.0.1:1026 127.0.0.1:1027 ESTABLISHED off (0.00/0/0) >> > tcp 0 0 204.179.131.123:1745 207.33.153.134:6667 ESTABLISHED on2 (7106.08/0/0) >> > tcp 0 0 204.179.131.123:1023 207.33.153.134:22 ESTABLISHED on2 (6455.34/0/0) >> > >> > If there would at least be a command to reset those times to make the >> > connection usable again.... This way I have to establish a new connection >> > to the same host to do something usable. >> >> Once you get through again TCP will reset the timeouts itself as it >> receives new ACKs. > >Whilst this is true, I think many people would describe a >protocol that allows 2 hour retransmits as broken. Were its >designers looking for reasonable results on links between the >Earth and Mars?
Actually, I believe they were looking for reasonable results with connections to Mars:
From tcp_timer.c:
tcp_retransmit_skb(sk, skb_peek(&sk->write_queue));
/* Increase the timeout each time we retransmit. Note that * we do not increase the rtt estimate. rto is initialized * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests * that doubling rto each time is the least we can get away with. * In KA9Q, Karn uses this for the first few times, and then * goes to quadratic. netBSD doubles, but only goes up to *64, * and clamps at 1 to 64 sec afterwards. Note that 120 sec is * defined in the protocol as the maximum possible RTT. I guess * we'll have to use something other than TCP to talk to the * University of Mars. * * PAWS allows us longer timeouts and large windows, so once * implemented ftp to mars will work nicely. We will have to fix * the 120 second clamps though! */ tp->backoff++; tp->rto = min(tp->rto << 1, 120*HZ); tcp_reset_xmit_timer(sk, TIME_RETRANS, tp->rto);
tcp_write_timeout(sk);
>This is quite a pain with TCP across unreliable media (e.g. the >Internet). A broken path gets fixed after some significant >downtime, but established connections take an age to pick up >again. There has be a Better Way.
Hmm... Move to Mars? ;o)
-- Mike A. Harris Linux advocate Computer Consultant GNU advocate Capslock Consulting Open Source advocate
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