Re: _Very_ strange network delay over dialup-ISDN in 2.2.11.
bvermeul@blackstar.nl
Fri, 20 Aug 1999 09:13:46 +0200
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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