CBWFQ

[annayuzhao]

What's the Queuing mechnism in each class?

What's the Queuing mechnism between the classes?

For example if I have two classes with bandwidth 64 and 128. Each class is defined by couple access-list. Obviously with each class there is a queuing mechnism and also the queuing mechnism between the classes.

I think maybe in the class it's WFQ, and between the class it's FIFO.

Any other thoughts? Thanks

[pbarman]

CBWFQ -- As the name goes, it is WFQ within the class. Bandwith is reserved for each class with the "bandwidth" command, so traffic conforming to that class will have this much amount of bandwidth.

Between classes, it is FIFO, whichever packet comes in it is compared to the access-list (or whatever criteria specified in map-class) and given that share of bandwidth, and sent out as FIFO. If a class is configured with "priority" command (LLQ), in that case all traffic in that class will be sent first before starting with other classes.

[annayuzhao]

Perfect. That's the answer what I expected. The other small question.I was reading the document saying by default CB queuing reserver 256 queues, but CBWFQ reserve 64. What I am wondering is how system knows that you are configuring CBWFQ or just CB. The reason I am asking this, I have done the following config in the router, but it says 256 queues as reserved, not 64.

policy-map test2

class test2

priority128

interface Serial0/0

ip address 10.1.40.2 255.255.255.0

service-policy output test2

show queueing fair

reserved queue still shows 256. Not 64.

But according to the cisco document, I list an example bellow stating it should show 64.

-----------------------------------------

Router#show queueing fair

Current fair queue configuration:

Interface Discard Dynamic Reserved Link Priority

threshold queues queues queues queues

Ethernet0 64 256 64 8 1

---------------------------------------------------

Thanks