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New Member

FRF.12 traffic shapping fragmentation queing

I have a quick q in regards to queing and FRF.12 traffic shapping fragmentation and queing

The cisco doco I am reading says WFQ or LLQ must be configured on the pvc ok

Frame relay traffic shapping must be configured on the interface.

The next page goes on to say that the only the only queing supported on a pvc when fragmentation is enabled is weighted WFQ is this correct ?

I would have thought that if we were using fragmentation It was to interleave critical traffic such as voice to overcome serialization delay & related issues such as jitter.

Now if WFQ is the only way to go then theres no priority que for voice.

I understand that WFQ can recognise IP TOS but if many flows are coming in

they will all recieve a fair service to fair even thats why we use more appropriate queing techniques PQ ip rtp CBWQ etc now if this PVC were bigger I wouldnt be doing fragmentation .

Fragmentation is performed after frames are removed from the que.Voice packets would not need fragmentation can LLQ be used here or not and why.

reference DQOS student guide volume 1.0 page 6-32 6-34

Cisco Employee

Re: FRF.12 traffic shapping fragmentation queing


On frame-relay circuit we want to make sure is traffic shaping is enable so the queu is serviced every 10 ms and minimize the delay and have control over bursty traffic. The other thing you asked is does WFQ enable when configuring traffic shaping... you are correct...

The other concern is if pvc is bigger you would not need fragmentation and at ths point should LLQ be used. The answer is yes.. The reason you want to use LLQ is to prioritize voice packets and assign guaranteed bandwidth when there is contention for bandwidth.



New Member

Re: FRF.12 traffic shapping fragmentation queing

Ok thanks .

To simplify the question

The book says on 1 page that you can use wfq or LLQ when using fragmentation

2 pages later it says that wfq is the only one supported.

There will be contetion when using WFQ as all ques are serviced

On a small pvc can you use fragmentation and LLQ oviously we wont be fragmenting voice traffic But Id like a priority que for it as WFQ is dynamic and once various different flows come on board it will service them =ly perhaps to fairly

thanks for the reply ; )

Cisco Employee

Re: FRF.12 traffic shapping fragmentation queing

If you noitce when you apply traffic shaping to the interface.. the main interface will be seen as fifo. At this point fair-queu will be or can be turned on at pvc level. Now if you enable fragmentation you will automatically have dual-fifo under your main interface and under your map class you will see fair-queu configured . What this means is unfragmented packets will move to priority queue at interface level, but if you like to prioritize traffic at pvc level then you should enable LLQ which will have strick priority over data and that queue will only have real time traffic. The priority queue will always be serviced first by the interface and move those packets do priority queue at the interface where you will have dual-fifo. The rest of the traffic from WFQ will be fragmented and moved to the second queue of the dual-fifo. Hope this will help...


New Member

Re: FRF.12 traffic shapping fragmentation queing

Yep thanks

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