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michaldieska
Beginner

QoS priority level 1-7 IOS-XR

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.

1 ACCEPTED SOLUTION

Accepted Solutions
smilstea
Cisco Employee

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

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3 REPLIES 3
smilstea
Cisco Employee

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

View solution in original post

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.

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