[c-nsp] RSVP QoS, CAC and HQF

[Mark Tinka]

On Tuesday, July 02, 2013 05:36:58 PM 
tkacprzynski at spencerstuart.com wrote:

> Hello,
> I'm working on setting up RSVP Call Admission Control for
> Cisco's call manager. I have the CAC working nicely, but
> my problem is with ensuring that the reserved bandwidth
> will actually get queuing reservation in the data plane.
> So my question is not voice specific but rather RSVP
> with DiffServ.
> 
> 
> After Cisco implemented HQF in 12.4(20)T they change the
> Weighted Fair Queuing to Flow-based Fair Queuing, which
> treats each flow equally. RSVP used to have a special
> reserved queue with a very low weight attached to it. 
> This low weight provided for preferred queuing. From
> what I have read RSVP does not do any classification of
> RSVP reserved packets, but is only a control protocol.
> If I were to use a LLQ to select only EF traffic for
> voice and have RSVP signal the reservation, how do I
> prevent other EF traffic from coming into that LLQ? Do I
> have to do it manually? Is there any sort of RSVP
> classification with HQF that will put flows matching
> reserved with RSVP into a special queue?

Not sure whether you ever got an answer to this, but you're 
basically looking at the merits of DiffServ vs. IntServ.

I have not used RSVP beyond a label distribution protocol as 
well as method to signal LSP's for MPLS.

Unless you have a specific need to go IntServ for your QoS 
model, what has been tested significantly in operator 
networks is DiffServ, where PHB's (per-hop behaviours) 
determine how traffic gets queued at every hop.

With DiffServ, queues in the core handle global traffic (so 
voice, voice signaling, video, e.t.c. would be, for example, 
marked as EF traffic). You would then need to provision 
sufficient bandwidth in your core to handle ALL EF traffic 
(regardless of what it is). Even though routers like the CRS 
can have discrete/multiple LLQ processing capabilities, you 
generally get to have just a single LLQ per (sub)interface.

Hope this helps.

Mark.
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