From: Nick Shah (nshah@connect.com.au)
Date: Thu Oct 10 2002 - 06:26:25 GMT-3
The strict priority queueing scheme allows delay-sensitive data such as
voice to be dequeued and sent first-that is, before packets in other queues
are dequeued. Delay-sensitive data is given preferential treatment over
other traffic.
plus
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120
t/120t5/iprtp.htm
Further on the same url, it says...
IP RTP Priority does not have per-call admission control. The admission
control is on an aggregate basis. For example, if configured for 96 kbps, IP
RTP Priority guarantees that 96 kbps is available for reservation.
If you see, it provides 'strict admission control' and acts before CBWFQ (or
WFQ) comes into play.
rgds
Nick
----- Original Message -----
From: Jayashanker Warrier <jwarrier@rediffmail.com>
To: <nshah@connect.com.au>
Cc: <ccielab@groupstudy.com>
Sent: Thursday, October 10, 2002 6:08 PM
Subject: Re: RSVP (CBWFQ / PQ-WFQ NOT RIGHT)
> Hi Nick,
>
> Even RTP kick in only when there is a congestion so the only
> option is RSVP (please correct me if i am wrong)
>
> Thanks
>
> Jayashanker
>
>
> At 07:35 10/10/2002 +1000, Nick Shah wrote:
> Ok, The reason LLQ or CBWFQ doesnt satisfy the requirements is
> because :
>
> - Remember CBWFQ kicks in only when there is congestion, so if you
> specify
> 40K b/w for class voice, that only comes into affect when there
> is
> congestion
> - When there is no congestion, VOICE traffic is free to use as
> much as it
> 'demand'
> - HEnce the Lab requirement of using 40KMax is not fulfilled.
> - Here's where RSVP reservation or IP RTP comes into play. because
> it uses
> either 40K or nothing it is the ideal choice.
>
> rgds
> Nick
> ----- Original Message -----
> From: Jaroslaw Zak <jaroslawz@hotmail.com>
> To: <clarson52@comcast.net>; <nshah@connect.com.au>;
> <CLarson@usaid.gov>;
> <ccielab@groupstudy.com>
> Sent: Thursday, October 10, 2002 1:18 AM
> Subject: Re: RSVP
>
>
> >Chris,
> >
> >For this particular question, how about LLQ, where you do
> >configure
> priority
> >queue for voice and specify minimum bandwidth (no need for ip
> >rtp) and you
> >can apply it per interface or per pvc, and you dont have to apply
> >that all
> >the way end-to-end (which is just a bad design anyway, but
> >satisfies your
> >task).
> >
> >Regards
> >Jarek
> >
> >
> > >From: Chris <clarson52@comcast.net>
> > >Reply-To: Chris <clarson52@comcast.net>
> > >To: Nick Shah <nshah@connect.com.au>, "Larson, Chris"
> <CLarson@usaid.gov>,
> > > ccielab@groupstudy.com
> > >Subject: Re: RSVP
> > >Date: Wed, 09 Oct 2002 06:53:17 -0400
> > >
> > >First, thanks for your reply. I appreciate it. My post was more
> >of a rant
> I
> > >spose.
> > > I am not really confused about the technology. I understand
> >RSVP,
> CBWFQ,
> > >WRED etc. etc.
> > >
> > >My post was mostly written out of frustration and confusion
> >with the lab
> > >authors questions and maybe labs in general. As stated before
> >the
> question
> > >was not real clear excpet to make 40k available to voice. Well
> >anyone who
> > >understands the technology would drop RSVP right away because
> >it is not
> > >configured anywhere else and therefore configuring it on this
> >one
> interface
> > >doesn't make sense and w/o going back to look at the lab prolly
> >wouldn't
> > >meet the requirement as putting it on this one interface does
> >not make
> 40k
> > >available to voice.
> > >
> > >This is my problem with a lot of lab questions. The fact that a
> >lot of
> them
> > >are far from reality. I can catch the subtle hints at what the
> >author
> wants
> > >at times but some are so vague.
> > >
> > >Here is another example. R3 and R4 are running ospf. They are
> >part of a
> > >larger network of course. On R3 and R4 there is serial and
> >isdn. On R3
> > >ensure that if the connection to R4 is lost that R3 can still
> >communicate
> > >with the rest of the network? What the hell is that? Since it
> >is in OSPF
> > >well a loss of ospf on either router will keep R3 from
> >communicating with
> > >the rest of the network. Having built a lot of networks in the
> >real world
> I
> > >would be inclined to do a demand circuit. However, the answer
> >was a
> backup
> > >interface. The way it is configured would not allow it to
> >communicate
> with
> > >the rest of the network, only with R4 (unless a default route
> >was added).
> > >I
> > >know..... I KNow.... it is a test to see if you understand the
> >technology
> > >not if you know how to use it well.
> > >I would suggest they move that stuff into the written and
> >expect a CCIE
> > >candidate to configure things that work and that would be
> >acceptable to
> the
> > >real world.
> > >
> > >Sorry, just a rant and I am done now. In my opinoin the real
> >lab is much
> > >less vague then some of these practice ones I have found
> >anyway. Thank
> > >goodness.
> > >
> > >
> > >
> > >----- Original Message -----
> > >From: "Nick Shah" <nshah@connect.com.au>
> > >To: "Larson, Chris" <CLarson@usaid.gov>;
> ><ccielab@groupstudy.com>
> > >Sent: Tuesday, October 08, 2002 10:54 PM
> > >Subject: Re: RSVP
> > >
> > >
> > > > Chris,
> > > >
> > > > You are right. I guess we should be lookign at the wording
> >of the
> > >question.
> > > > That would be a giveaway. Plus our understanding of the
> >underlying
> > > > technology.
> > > >
> > > > For example. CBWFQ doesnt kick in until there is a
> >congestion, when
> > >there
> > >is
> > > > a congestion you get the specified b/w (specified in the
> class/policy).
> > >It
> > > > also doesnt take care of serialization delay, jitter (what
> >if the
> > >interface
> > > > is transmitting a large packet just around the time your
> >voice packet
> > >comes
> > > > in, voice packet waits).
> > > >
> > > > With RSVP, the required b/w is signalled at the beginning of
> >the
> > > > conversation, if required b/w is not available tough luck,
> >no call
> made.
> > > > This reservation is made end to end. And you may also need
> >to specify
> > > > 'req-qos guaranteed delay or req-qos controlled load' under
> >dial
> peers.
> > > >
> > > > With RTP priority, you use it when you are asked to
> >strictly
> prioritise
> > > > voice and all else use CQ or WFQ. so you specify ip rtp
> >priority
> <port>
> > > > <port> bw. Use it when you have to prioritise VOICE above
> >all others.
> > > >
> > > > And then there is frame relay fragmentation , if data &
> >voice traffic
> > >takes
> > > > a single PVC path.
> > > > or DLCI prioritization along with PQ if using different
> >PVC;s for
> > > > VOICE/DATA/whatever else.
> > > >
> > > > Plus remember where the technologies can be implemented, on
> >the edge
> or
> > >in
> > > > the core, for TCP or UDP. Like WRED can be used for TCP (TCP
> >"adapts",
> > >UDP
> > > > doesnt), but for UDP its not really helpful.
> > > >
> > > > We can virtually use any/every queuing technology depending
> >on a
> > >scenario.
> > > > (WFQ even). It will all depend upon the wording of the
> >question and
> what
> > >is
> > > > allowed/expected/disallowed etc.
> > > >
> > > > Hope, I have not confused you more :) than you already
> >were.
> > > >
> > > > BTW, in your question, you cant use CBWFQ because the
> >specified b/w in
> > >cbwfq
> > > > is 'minimum' amount of b/w usable during congestion, so rule
> >it out of
> > > > equation.
> > > >
> > > > You could use either RSVP or RTP.
> > > >
> > > > rgds
> > > > Nick
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: "Larson, Chris" <CLarson@usaid.gov>
> > > > To: <ccielab@groupstudy.com>
> > > > Sent: Wednesday, October 09, 2002 12:13 AM
> > > > Subject: RSVP
> > > >
> > > >
> > > > > I had a question in a lab scenario that called to make 40
> >k
> available
> > >to
> > > > > voice traffic. My first thought was ip rtp priority with a
> >40k max
> > >limit.
> > > > > However the solution calls for RSVP.
> > > > >
> > > > > Nowhere else is RSVP configured. Based on what I know
> >about RSVP
> this
> > > > could
> > > > > not be correct. RSVP requires configuration all along the
> >paths
> right?
> > >How
> > > > > would a person determine they are asking for RSVP? For
> >that matter
> how
> > > > would
> > > > > you know if they are asking for CBWFQ? It could be used
> >to
> accomplish
> > >the
> > > > > same thing if the acl were setup rightin the class map?
> > > > >
> > > > > I would think that if a solution called for RSVP the
> >question would
> > >state
> > > > to
> > > > > reserve a certain amount of bandwidth, not make available.
> >Thoughts?
> > >How
> > > > to
> > > > > determine what a given question wants in the way of QoS.
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > Christopher Larson - CNE, MCP+I, CCNP + Security
> > > > > Open Systems Sciences Corp.
> > > > > USAID Information Resources Management (contractor)
> > > > > 202 712 4559
> > > > > clarson@usaid.gov
> >
> >
> >
> >
> >_________________________________________________________________
> >Join the world's largest e-mail service with MSN Hotmail.
> >http://www.hotmail.com
>
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This archive was generated by hypermail 2.1.4 : Tue Nov 05 2002 - 08:35:44 GMT-3