QOS settings on my 2960 switch - explain please

[carl_townshend]

Hi all

I am getting into some QOS config and would like to understand the sistuation a little better on my switches.

Can someone please explain the following

1.Which QOS values are normally mapped to which queue

2.Which queue is normally the high priority queue

3.What is the threshold settings

4.How do I display which values are assigned to what queue

5.Lastly when applying QOS would we normally assign to the output queue (egress), when would we apply on the input queue and why ?

Many thanks

Carl

[jonathanaxford]

Hi Carl,

There is some great information on 2960 QoS in the software config guide:

http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_44_se/configuration/guide/swqos.html#wp1021811

I'll have a stab at your questions...

1) Guess it depends on what you are doing and what you are trusting. We map all DSCP EF (46) to the priority Queue - Q1 on the 2960 and all Call signalling CS3 traffic to Q2. Default 0 traffic goes down Q4. This is all based on a Cisco Auto Qos config which fitted well to our environment, supporting Cisco Voice.

2) Depends on the model, on a 2960, Q1 is the priorty queue, on a Cisco 6509 WS-X6748-SFP module, its Q4.

3) Threshold settings set up various paramters such as queue buffer sizes and weighted tail drop values... the doco above will have more info on this.

4) If you do a show run you can see the output dscp-map/output cos-map entries whihc indicate what queues each of the QoS values is assigned to.

5) Not sure what you mean by this? In our environment, supporting VoIP on all access switches, we use QoS on everyswitchport and uplink - it's patr of our standard config BUT, this is a simplistic setup so it depends entirely on your needs.

Hope this helps a little,

Jon

[carl_townshend]

Hi

many thanks for your help

I mean for the last question, when applying the service policy for example where would we apply it, input or output? by default when say im just trusting qos values, when we are talkign about the queing for this does it apply to the input or output queue of the interface?

cheers

[Shashank Singh]

Hi Carl,

service policy can be applied both on ingress and egress depending on the requirements. If you configure service-policy input, it applies to the traffic coming in on this port and vice versa for service-policy output.

service-policy input can affect queuing of data in ingress and service-policy output can affect queuing of data in egress.

Hope this helps.

Shashank

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