ipfw bandwidth shaping problems (intermittent latency)

[Andy Coates]

Hi,

Up until now I've been fairly happy with just using a simple pipe with:

  pipe 1 config bw 2400Kbit/s

However recently under a more utilised link we start to see every third
packet or so have a higher latency than the rest.  For example, an icmp
ping to the host would show 10ms, 10ms, and then 190ms, then back to 10ms
for another 2 pings and upto 190ms again.

I decided to play with the queue settings, and tried:

  pipe 1 config bw 2400Kbit/s queue 15

This then brought that third ping down to 70ms, so an improvement.  This
still isn't acceptable however, since the amount of bandwidth being used
is only 1000Kbit/s so I can't see where the problem is.

Is there anything else I can change to improve the response/latency? Or
is this some type of bug?

Thanks in advance.

Andy.