thr3ads.net - LARTC - Data rate accuracy started failing. [Oct 2003]

Dear all,

  I am an experienced unix administrator and a long time ago (1+ year)
  I made traffic-shaping system for an ISP (~400 clients).

  Each ip address requires 4 classes -
   2 for incoming (internet->client), one for international traffic,
     the other for local-country and border-country traffic.
     and
   2 for outgoing (client->internet), for the same purposes.

 Everything worked ok until last week, when more clients
 were added. The data rate (rate NNkbit) is no longer stable -
 sometimes it exceeds the rate specified and sometimes
 there is starvation. And no, there is still planty of traffic
 left, so its not a problem of bandwidth capacity.

 The technique used is htb + sfq for traffic exceeding 0.8mbit/s,
 for traffics up to 0.8mbit/s as it is not cpu-intensive
 (but depends on HZ for calculations)

 Are there any limits I am not aware of? It seems that everything
 works ok again if I remove some addresses (single address /32 or
 larger networks). I am not sure which part fails, filtering
 or actual shaping.

 And, it is vanilla Linux 2.4.20 with qos services coming with
 it.

 Also, i never came up with the other question: there has always
 been problem with tbf. For example, rate 256kbit is specified but the
 actual rate never exceeds 230 - 250kbit, so I add 30kbit for each
 rate (so 256 becoms 286kbit) so client got exactly his 256kbit.

thanks,
P.Krumins