[altq:1679] Re: Unstable cbq on Openbsd box

[Nicolas Christin <nicolas@cs.virginia.edu>]

On Thu, 17 Oct 2002, Danny Kjærgaard wrote:

> Im running a altqd on a OBSD3.1 box. I cant get my conf to run like
> i want it. The problem is that when i start an ftp connection to the
> altq server and start downloading the speed is like 30k like i should.
> The after some time it drops do 22k for 2-3 secs. then back up at 30k
> agin. It does this all the time. I tried to make the bandwidth bigger
> but i didnt help. I compile my kernel with the kernel option that
> emulates the 256GHz cpu. Can somone help me ?

With such a coarse level of details, it's hard to do anything but take
a wild guess. It sounds like a TCP back-off to me. (You drop too many
packets in a row, and the source ends up reducing its congestion window
size very drastically, possibly back to slow-start). Making the
"bandwidth bigger" wouldn't change a thing, you would still end up
dropping packets, ultimately causing a decrease in throughput.

Please provide your altqstat output. What do you use to measure the
throughput of your FTP flow?

-- 
Nicolas Christin
Ph.D. Candidate, University of Virginia, Computer Science
http://www.cs.virginia.edu/~nicolas