QoS priority level 1-7 IOS-XR

[michaldieska]

Hello guys,

could someone share more info about the introduced QoS feature (from IOS-XR 5.3.2) to support up to 7 priority levels in LLQ?

RP/0/RP0/CPU0:at0f2a-r2n0-gr(config-pmap-c)#priority level ?
 <1-7>  Priority level

I was aware of only about priority levels 1-2 where level1 has higher priority than level2 but both are high priority queues.

Now I am little bit confused as there is no good description of this new capability.

What is the relationship between those different 7 levels now?

How they behave and what is the benefit to have 7 different priority queues?

How to map this to the 8Q/16Q model?

Any help would be much appreciated.

Thank you a lot.

[smilstea · Accepted solution]

Priority level 1 is highest, then 2, and so on in descending order until we get to priority none. As it is a strict priority mode, there is a possibility that traffic on lower priority queues will be starved as long as there is continuous traffic on higher priority queues.

Sam

[michaldieska]

Hi Sam,

thank you very much for your reply. I am wondering what is the purpose/usage example to have so many PQs? When there were only 2 PQs, usual usage was to have 1 PQ for Voice and another PQ for Video, but 7 PQs?

Are there any restrictions to use those 7 priority queues?

I didn't find too much information about this feature in cisco webpages, do you know about some good documentation about this?

Thank you again Sam,

have a nice day,

Michal.

[smilstea]

One example would be if you had the typical QoS classes of video, voice, business class, scavenger / best-effort, etc then you can assign a PQ to each one.

There isn't much in the way of configuration except to assign priority level x to the class.

Sam