From: Chris (clarson52@comcast.net)
Date: Wed Oct 09 2002 - 07:53:17 GMT-3
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
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