From: Petr Lapukhov (petrsoft@gmail.com)
Date: Wed May 10 2006 - 02:22:05 ART
Excellent, topic here!
Now, the only thing i could quickly find on DocCD for RSVP/LLQ is
http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_white_paper09
186a0080080204.shtml
It has one excellent picture, that cleared my thoughts a little.
This is how i get it:
First of all, RSVP is not just a signalling mechanism. It also has idead of
classification, based on concept of flow.
Next, RSVP was originally implemented to work with WFQ (reserved flows) -
due to it's flow-based nature. RSVP defines a set of reserved queues within
WFQ, that have lower weights than other flows.Note that this is not
a strict priority queueing, so RSVP is not always served first.
Then a concept of strict priority was introduced into WFQ - IP RTP priority.
Now, what should we do, when a voice flow is classified to be under RSVP
reservation? Cisco introduced a concept of "ip rsvp pq-profile", that could
direct some of RSVP flows into PQ.**
Finally, PQ+WFQ mutated to LLQ/CBWFQ, as we know it by now.
But still, this concept is based on original PQ+WFQ idea. So I think
RSVP would work great with modern LLQ as well.
This is what you can see on a picture - after all classifications been done,
we have one priority queue per interface (this is where RTP priority and
class priority are merged). Still RSVP could direct some of it's flows into
this queue.
But as I get it, this priority queue "reserved bandwidth" is based on
LLQ/RTP
Priority configuration. RSVP bandwidth is bandwidth (weigth) defined for
reserved
flows within WFQ.
I'll try to verify RSVP with modern LLQ in my lab as soon as possible, since
i'm interested in results too :)
HTH
Petr
2006/5/10, James Ventre <messageboard@ventrefamily.com>:
>
> Thought you might find this interesting
>
> By: Pete Welcher
> http://www.netcraftsmen.net/welcher/papers/smorgasbord01.html
>
>
> "I recently did some work that lead to heavily reviewing the (sparse)
> Cisco RSVP documentation. The documentation really doesn't say much
> about how RSVP actually works in the Cisco routers. In particular, the
> documentation does say RSVP works with weights with WFQ. Fine, I believe
> that, and I know enough about that to believe it probably does what is
> needed. Does RSVP also do that with CBWFQ/MQC? Not documented, as far as
> I could see. The RSVP LLQ feature is mis-titled, it is really Priority
> Queueing with WFQ, a far different thing. Etc. I ended up with the
> feeling that the only thing Cisco RSVP seemed guaranteed to work with
> was WFQ. "
>
>
> James
>
>
>
> Jian Gu wrote:
> > Hi, could any one please give me a pointer which explains how RSVP is
> > configured to work with LLQ for voice traffic? my understanding is that
> RSVP
> > is just a signalling protocol, it still depends individual router's LLQ
> > implementation to guarantee bandwidth for voice, but if LLQ is
> configured
> > for voice traffic in every router, why do we need RSVP at all for voice?
> >
> > Jian
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Thu Jun 01 2006 - 06:33:21 ART