[rbak-nsp] priority queuing issue

[Brian George]

Hi Thomas,

Thanks for the reply.  I tried setting the burst to 1.5 seconds of traffic at the rate and it didn't help.  The reason I have it set there to 15000 is because the manual states for pq burst to be 10 times the interface mtu.

Does anyone know how how a pq policy knows the rate at which congestion is occurring?  If rates are set for each queue in use does it use that total as the max rate for the circuit?  for instance I have this policy bound to a vlan on a gige port, so the rate at which there is congestion as far as this circuit is concerned would be less than the port speed.

Edrr policies work well for this but the 15 policy limit per card isn't cutting it.  Maybe someone has some ppa2 based eth cards they want to sell cheap :)

Thanks,
Brian




-----Original Message-----
From: Voigt, Thomas [Thomas.Voigt at netkom.de]
Received: Friday, 22 Jun 2012, 4:51am
To: redback-nsp at puck.nether.net [redback-nsp at puck.nether.net]
Subject: Re: [rbak-nsp] priority queuing issue


Hi,

Brian George wrote:

> I have a pq profile set up w/ 4 q's, each assigned a rate.  According to the manual when there is no congestion the rate limit should not be imposed, however I am seeing queue rate being enforced even when no other traffic is offered.  I'm running  v 6.1.4.6.

You are right, George.
As long as there is no congestion all queues can use higher bandwith than the configured. If you like to disallow one queue to use a higer rate, if there is no congestion you have to use the "no-exceed" keyword.

> qos policy pq-test3 pq
>  num-queues 4
> queue 0 rate 5000 burst 15000
> queue 1 rate 20000 burst 15000
> queue 2 rate 50000 burst 15000
> queue 3 rate 30000 burst 15000

But I see a possible problem in your config:
Your burst rates don't follow the guidelines from the manual. So it could be possible, that you've got some unexpected bandwith rates.

The manual states, you have to calculate the burst rates as follows:

The burst rate has to be configured as the number of bytes which are transferred in 1.5sec with the given rate.

So if you like to configure a rate of 5Mbit/s your burst size should be 5000000Bit/s * 1.5 / 8 = 937500 Bytes

Hope this helps.

--
regards

Thomas