Messages in this thread | | | Date | Tue, 14 Sep 1999 22:27:39 +0000 | From | Marc Mutz <> | Subject | Re: _Very_ strange network delay over dialup-ISDN in 2.2.11. |
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David Woodhouse wrote: > <snip> > > This sounds familiar. I had a similar problem a few months ago. There were > always a constant number of packets in the outgoing queue. If I ran tcpdump on > the ISDN interface, I could see them being sent out. TCP connections would > stall, unless I ran ping across the link to keep the queue moving. ping -f > would make packets go out almost immediately (chronologically speaking). > > I didn't ever manage to find out the cause of the problem. It used to take > some days of connectivity before it would happen, so I couldn't easily debug > it. Eventually we installed a leased line to replace the ISDN, so I have no > clue if it's still happening. > > I was using the CVS ISDN code at the time - the standard code wouldn't work > with the Teles 16.3c IIRC. >
I just fell over this problem again, this time in 2.2.12. Haven't had it for two weeks or so, but I must admit that I don't run ping continuously anymore to keep the link up. Instead, I do the following loop:
while netstat -n | grep tcp | grep -v 127.0.0; do ping -c 5 $PEER_IP sleep 4 done
This has revealed some other aspect of the problem, although I guess they are *but differnt manifestations:
- ping times over an otherwise unused link go from 40ms to 1040ms, ie. up by exactly one second, the ping interval. - the above loop almost always shows many connections of the from tcp 1 0 ... CLOSE_WAIT that won't go away for minutes. ping -f will not flush these! Example real-world output follows: tcp 1 0 129.70.37.20:2143 129.70.4.50:8080 CLOSE_WAIT tcp 1 0 129.70.37.20:2142 129.70.4.50:8080 CLOSE_WAIT tcp 1 0 129.70.37.20:2141 129.70.4.50:8080 CLOSE_WAIT tcp 1 0 129.70.37.20:2140 129.70.4.50:8080 CLOSE_WAIT tcp 1 0 129.70.37.20:2139 129.70.4.50:8080 CLOSE_WAIT tcp 1 0 129.70.37.20:2138 129.70.4.50:8080 CLOSE_WAIT tcp 1 0 129.70.37.20:2137 129.70.4.50:8080 CLOSE_WAIT tcp 1 0 129.70.37.20:2136 129.70.4.50:8080 CLOSE_WAIT tcp 0 1 129.70.37.20:2132 128.32.18.166:80 SYN_SENT
So this indicates that the same problem as described by David is present here, with a queue length of one.
-- Marc Mutz <Marc@Mutz.com> http://marc.mutz.com/ University of Bielefeld, Dep. of Mathematics / Dep. of Physics
PGP-keyID's: 0xd46ce9ab (RSA), 0x7ae55b9e (DSS/DH)
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