1p1q4t Receive Priority Queue

Unanswered Question
Sep 10th, 2009

I have a WS-X6408A-GBIC line-card in my 7609. I am doing QOS on this router, but what is odd to me is that my COS 5 value is not mapped to my Rx strict-priority queue 2?

This does not look normal, but maybe it is?? I have seen other examples with the same queuing structure and COS 5 is mapped to the queue 2. This is what the Rx queuing looks like on one of my Gig interfaces:

Queueing Mode In Rx direction: mode-cos

Receive queues [type = 1p1q4t]:

Queue Id Scheduling Num of thresholds


1 Standard 4

2 Priority 1

queue tail-drop-thresholds


1 100[1] 100[2] 100[3] 100[4]

queue thresh cos-map


1 1 0 1 2 3 4 5 6 7

1 2

1 3

1 4

2 1

Packets dropped on Receive:

BPDU packets: 0

queue thresh dropped [cos-map]


1 1 0 [0 1 2 3 4 5 6 7 ]

* - shared receive counter

As you can see, COS values all mapped to Rx queue 1. I appreciate your help!



I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4 (1 ratings)
eknell Thu, 09/10/2009 - 12:28


I have actually tried that, "priority-queue cos-map 1 5" and it does nothing. It says something like propagating to all interfaces, but when I look at the queuing on the interface, nothing changes?

Do you happen to know how to manually change it to Q2?

Thanks again..

Edison Ortiz Thu, 09/10/2009 - 12:45

The link I posted also indicates the Queue will always be 1.

I don't have an equipment at the moment for testing, if you wish - you can open a TAC case.

I also want to point out, you should concentrate on egress priority queueing to be functioning as ingress priority queueing does not provide as much benefit.



eknell Fri, 09/11/2009 - 10:36


I appreciate it, but all of my egress queuing is configured correctly, which why I am interested in the ingress portion. It seems to be a QOS issue and am just double checking everything, ya know?

Let me ask you this. Have you ever heard RTP packet reordering across a 2 Gig Etherchannel before? Maybe something like Interleaved packets causing VoIP issues??

I don't even know if this could be a cause for our VoIP issue, I am just having to start to look at other things besides QOS that could cause quality issues.

Thanks for you responses!

Edison Ortiz Fri, 09/11/2009 - 10:50

Let me ask you this. Have you ever heard RTP packet reordering across a 2 Gig Etherchannel before?

Not on EtherChannel as the traffic is per flow - in other words - you won't have RTP traffic equally balanced hence no reordering on the inter-switch link.

Maybe something like Interleaved packets causing VoIP issues??

Interleaving is tied to MLPPP, no issue with Giga EtherChannel.



eknell Fri, 09/11/2009 - 11:19

Thanks again!

By the way, I had already opened a TAC case a couple weeks ago on this issue. They went through all my QOS configurations with a fine tooth comb, across every router and switch hop and they said everything was provisioned correctly, which is why I am trying to think "outside the box".

I am dealing with calls that traverse 3 PBX's, 2 being VoIP PBX's with the last VoIP PBX SIP trunking to the 3rd Class5 Phone switch, across our fiber backbone with multiple router and switch hops?!

You can see I have so many variables in the mix, and it is like trying to find a needle in a hay stack!

Anyhow, I will quit rambling. Again, I appreciate your help! Have a good one!


This Discussion