[LARTC] (simplified) Rate precision

[LARTC] (simplified) Rate precision

[Peteris Krumins]

 Hello gentleman,

  i wrote a few days ago but did not receive any answers.

  I simplified the problem and even wrote a quick example
  which demonstrates the innacurate rate precision:

tc qdisc del dev eth0 root >/dev/null 2>&1
tc qdisc add dev eth0 root handle 1: htb
tc class add dev eth0 parent 1: classid 1:101 htb rate 2048kbit
tc qdisc add dev eth0 parent 1:101 handle 101: sfq perturb 10
tc filter add dev eth0 protocol ip parent 1: prio 5 handle 101 fw flowid 1:101
iptables -A PREROUTING -t mangle --src <ip_address> -j MARK --set-mark 101

  The example above should shape the speed to 2mbit (2048kbit) but
  unfortunately the real speed is only 1920kbit..

  Tthe only solution I have found is to add the missing rate.

  Linux 2.4.20 vanilla.

  Any comments?


P.Krumins

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Re: [LARTC] (simplified) Rate precision

[Andreas Klauer]

Am Saturday 01 November 2003 21:32 schrieb Peteris Krumins:

>   i wrote a few days ago but did not receive any answers.

I did not receive/read this mail.

>   The example above should shape the speed to 2mbit (2048kbit)
> but unfortunately the real speed is only 1920kbit..

How exactly do you measure the 'real speed'? The difference sounds much like
overhead of some sort that you're not accounting properly. For example, when
using scp to copy files over the line, it would be normal to have lower
transfer rates than the actual line speed, because there's some kind of
handshake/encryption overhead with every package sent.

Regards,
Andreas Klauer

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