Two class-map priority statemetns under one policy map. Who has the priority?

[allensurface]

If I configure a policy map such as the one below, who has the actual  priority?

policy-map WAN-EDGE
class VOICE
  priority 512
class  CALL-SIGNALING
  bandwidth 12
class VIDEO
  priority 1024
class  class-default
  fair-queue

[sean_evershed]

In this case you have two low latency queues. Thererfore voice will get a reserved bandwidth of 512K and video will get 1024K of reserved bandwidth.

[allensurface]

I understand that there will be two LLQ's, but I am wondering who is going to

get queued first. For instance,assume the link is saturated and the priority queues are guaranteeing the 512 and 1024 each. The video traffic sends a large amount of data and large packets while their is a voice call on the same link. Would the voice data have to wait for the video? With one strict priority queue, the answer is obvious, the strict prioty queue traffic would get queued to the interface. But, with two priority queues, I can't see where one would be preferred over the other. I seem to recall reading somewhere that both traffic would be queued, but they would be competing with each other, essentially breaking the strict priority queue.

[samavedula_rama · Accepted solution]

As you very well know, LLQ is CBWFQ+Priority Queue. So, essentially, there is only one strict priority Queue. Just like we have 'HIGH' priority queuing in legacy method.

So, no matter how many priority queues you configure, they will still be one single queue. Inside the Queue the mechanism is still FIFO. So, if a voice packet comes then it goes first and if a video streaming packet comes it goes first, etc.

However I am not sure if it is the sum of Priorities that would end up as total priority.   Need to lab it up and check

Hope it helps.

[allensurface]

Rama, that is what I wanted to confirm. I thought that was the case as I thought I remembered studying that, but couldn't remember. Thanks for the clear answer!