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Question on RSVP / WFQ and LLQ

Hola Forum,

In first place, please sorry me if this is not the correct forum to do this kind of question, and if so I would appreciate if you can point me where to do this question.

Well I was reading a couple of Cisco links and playing with router to test the RSVP Application, As far as I know, RSVP is a signaling method used by network devices to accommodate QOS for the flow specified in the PATH and Resv Message transmitted

Here is a picture oriented link:

ok, say that I reserved certain resources to voice traffic, and I have configured in all my network this 2 commands

ip rsvp bandwitdh 300 20


I've been reading this link and this is where I just can not seem to understand if I need to use LLQ with RSVP or if using only WFQ with RSVP is enough to transmit delay sensitive packets like voice?? Do I need to enable other methods like LLQ or IP RTP Priority to make this work??


Step 3

Router(config-if)# fair-queue

Enables WFQ on an interface with priority queuing (PQ) support.

RSVP uses WFQ to provide fairness among flows and to assign a low weight to a packet to attain priority. However, the preferential treatment provided by RSVP is insufficient to minimize the jitter because of the nature of the queueing algorithm itself. As a result, the low latency and jitter requirements of voice flows might not be met in the prior implementation of RSVP and WFQ.

Also I saw that there are 2 commands that I just can not find a complete documentation about the functionality other than the command reference

ip rsvp pq-profile voice-like


R1(config-if)#ip rsvp resource-provider ?

none Associates NO resources with reservations

wfq Associates WFQ resources with reservations

I would highly appreciate if you can explain this a little bit more, and if possible provide a Cisco Documentation specific to this

Many thanks in advance




Re: Question on RSVP / WFQ and LLQ


when combining WFQ and RSVP then LLQ is not needed. The underlying reason is, that WFQ already will prioritize the traffic flows described by RSVP. To do this RSVP flows will have a "virtual ip precedence of 1024". This means, RSVP packets will nearly always be sorted to the front of the WFQ queueing system.

WFQ itself just uses the finish time approach and uses a hash to determine the queue to sort in a flow. This means a voip call could eventually end up with another flow (f.e. FTP) in the same queue. Thus no jitter and delay guarantees can be given to voip with WFQ alone (without RSVP or LLQ).

Hope this helps! Please rate all posts.

Regards, Martin

Community Member

Re: Question on RSVP / WFQ and LLQ

Martin, thank you so much for your explanation, Just another question,

If I use FRF.12 do I need to have a method to distinguish between unfragmented packets?

like frame-relay ip rtp??, using WFQ and RSVP??

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