network problems?

Robert Watson rwatson at
Thu Apr 19 10:03:37 UTC 2007

On Thu, 19 Apr 2007, Krassimir Slavchev wrote:

> The problem is when I try to access ftp servers, the connection stalls 
> randomly. Also I can't do cvsup and fetch. This happens only with machines 
> running -current and when the traffic is passed through router based on 
> FreeBSD 4.4. One of the test machines is my notebook which have installed 
> 7.0-CURRENT (from today) and 5.4-STABLE and I see this problem only with 
> -current.
> Is there any new features in -current tcp stack which may be incompatible 
> with FreeBSD 4.x?

No, not in principle, and ideally also not in practice.

Sounds like a bit more diagnosis is needed, though.  The first thing we should 
try to determine if this is a problem with a device driver, the network stack, 
or applications.

If you run ping on one terminal to the local router, does it experience 
problems at the same time as other applications?  I.e., does ftp stallage 
align with ping stallage?

Are there any console messages suggesting driver problems, such as messages 
about interrupts, timeouts, and so on?

If you run "vmstat -i", is there any device with an extraordinarily high 
interrupt rate (second column over 10000 or so)?

Could you try doing your network tests directly with the local router and 
avoid using the wide area network?  This would help avoid having wide area 
issues affect your testing, and also demonstrate whether or not you can 
reproduce it in a purely local setup (much easier to debug).

Robert N M Watson
Computer Laboratory
University of Cambridge

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