Re: 3560 - Why is output queue 1 always limited to 400k with

From: Petr Lapukhov (petr@internetworkexpert.com)
Date: Tue Sep 30 2008 - 15:46:17 ART

Could you post your full configuration? I just ran a quick simulation and it
works just as it usually worked for me: PQ steals all the bandwidth. E.g.
between Prec 0 and Prec 5 traffic:
interface FastEthernet0/1
 speed 10
 srr-queue bandwidth limit 20
 priority-queue out

Rack1R1#show policy-map interface fastEthernet 0/0
 FastEthernet0/0

  Service-policy input: METER

    Class-map: PREC0 (match-all)
      23 packets, 34822 bytes
      30 second offered rate 1000 bps
      Match: ip precedence 0

    Class-map: PREC5 (match-all)
      22739 packets, 34426846 bytes
      30 second offered rate 1956000 bps
      Match: ip precedence 5

If you change the speed limit to 30% the situation becomes as following:

Rack1R1#show policy-map interface fastEthernet 0/0
 FastEthernet0/0

  Service-policy input: METER

    Class-map: PREC0 (match-all)
      136 packets, 205904 bytes
      30 second offered rate 1000 bps
      Match: ip precedence 0

    Class-map: PREC5 (match-all)
      96488 packets, 146082832 bytes
      30 second offered rate 2716000 bps
      Match: ip precedence 5

That is, the PQ claims all bandwidth again.

HTH 

-- 
Petr Lapukhov, CCIE #16379 (R&S/Security/SP/Voice)
petr@internetworkexpert.com

Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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2008/9/30 Hobbs <deadheadblues@gmail.com>

> Hello,
>
> I know this is lengthy but I am completely stumped. I have been reading and
> labbing some of the examples of 3560/3550 qos on IE's blog and I have run
> into some interesting issues in my lab.
>
> R1----\
> R3----[SW1]----[SW2]-----R2
> R5----/
>
> All ports set to 10M. R1=cos1, R3=cos3, R5=cos5, default cos-output-q map.
>
> R2 has a policy with classes that match precedence (1,3,5) applied to its
> interface to meter the rate of each class.
> On each router I run this command: "ping 192.168.0.2 rep 1000000 size
> 1500"
> to generate a bunch of traffic. This works great.
>
> Whenever I have priority-queue out on f0/13, cos 5 is always limited to
> 400,000K no matter if I have a "srr-queue bandwidth limit" or not. In
> addition, the other queues eat up the rest of the bandwidth (unless I shape
> them of course). In other words, priority queuing is NOT starving the other
> queues.
>
> Any other settings I need to check? From what I understand share/shape
> parameters on queue 1 don't matter when priority queue is on, and in fact
> they don' t affect it - 400K is always the limit!
>
> thanks,
>
> the blog is here for reference:
>
> http://blog.internetworkexpert.com/2008/06/26/quick-notes-on-the-3560-egress-queuing/
>
>
> Blogs and organic groups at http://www.ccie.net
>
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