Messages in this thread | | | Date | Fri, 20 Aug 1999 09:13:46 +0200 | From | bvermeul@blacksta ... | Subject | Re: _Very_ strange network delay over dialup-ISDN in 2.2.11. |
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In mailinglist.linux.kernel, you wrote: > >Marc@Mutz.com said: >> I just experienced a very wierd network delay: I use a ISDN dialup >> line to my university. Normally I do not run ping, so this is - apart >> from a similar occurence with up to 20 sec lags in 2.2.10 - the first >> time I noticed this behaviour. But this time I wanted to keep the >> connection established. So I fired up ping, and saw that it reported a >> round-trip time of 1 second (1000 ms)! > > >Marc@Mutz.com said: >> it could only be resolved by shutting down the ISDN system (/sbin/ >> init.d/i4l stop) and starting it again. > > >Marc@Mutz.com said: >> Anyone got a clue? > >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.
Seen that, worked around it... :) There are two ways to work around this particular problem: Disable VJ compression on your ISDN link (-vj -vccomp I believe it is on the ipppd commandline), or disable tcp_timestamps. One way or the other the tcp_timestamps bite the VJ compression, if you disable either one, you get your normal, fast link.
Regards,
Bas Vermeulen
-- "God, root, what is difference?" -- Pitr, User Friendly -- Pitr, User Friendly
"God is more forgiving." -- Dave Aronson -- Dave Aronson
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