From: Scott Morris (swm@emanon.com)
Date: Tue Jul 27 2004 - 11:40:09 GMT-3
Heheheh... Kinda like the Hotel California... You can check out, but you
can never leave. ;)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Jay
Greenberg
Sent: Tuesday, July 27, 2004 10:34 AM
To: Veerman, Leigh
Cc: ccie2be; trouse@cisco.com; Yasser Aly; ccielab@groupstudy.com
Subject: RE: VOIP over ATM or FR
I guess you're SOL then. Once you're subscribed to a mailing list, you can
NEVER get off. Sorry!
On Tue, 2004-07-27 at 10:27, Veerman, Leigh wrote:
> How do I unsubscribe from this email group????
>
> I cannot handle the volume of mails
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of ccie2be
> Sent: 27 July 2004 15:21
> To: trouse@cisco.com; 'Yasser Aly'; ccielab@groupstudy.com
> Subject: Re: VOIP over ATM or FR
>
>
> Sorry, I can't answer that question. In the lab, if there's any
> question about what you need to do, I would ask the proctor.
>
>
> ----- Original Message -----
> From: "Terrence Rouse (trouse)" <trouse@cisco.com>
> To: "'ccie2be'" <ccie2be@nyc.rr.com>; "'Yasser Aly'"
> <yasser.aly@noorgroup.net>; <ccielab@groupstudy.com>
> Sent: Tuesday, July 27, 2004 9:44 AM
> Subject: RE: VOIP over ATM or FR
>
>
> CCIE2BE,
>
> Thanks for the insight. I guess my initial question is geared more
> specifically to a CCIE lab scenarios. We all know that "real world"
> is different than practice and CCIE labs. So my question really was
> more of....."if not stated in a CCIE lab task, should you still
> configure the
> L2
> QOS to support voice traffic." In other words is it mandatory to avoid
> breaking data communication. For example in F/R: you have LLQ, FRTS
> with tc=1/100, FRAGMENTS. If so what are the issues. This is
> important because in real lab things may appear to work just fine, but
> if they expect to see the proper QOS and you don't configure it, then
> you get no points. Know one knows how these are graded but little
> tidbits like this may help someone be more thorough on the solution.
>
> Thanks again, great info. I will be reading over all those books again.
> Its been a while, need to dust them off. :-)
>
>
>
> -----Original Message-----
> From: ccie2be [mailto:ccie2be@nyc.rr.com]
> Sent: Tuesday, July 27, 2004 8:24 AM
> To: Yasser Aly; trouse@cisco.com; ccielab@groupstudy.com
> Subject: Re: VOIP over ATM or FR
>
>
> Yasser,
>
> You've got this all confused.
>
> For example, if you ping an ip address ( and get a response), do you
> have do to anything special if the ping travels over a ATM or F/R
> circuit or ethernet or token ring or sonet or 802.11b wireless? The
> answer, of course, is no.
>
> The ping doesn't care what the layer 2 link technology is. Why is that?
>
> Because at each link's interface, the router takes care of
> encapsulating the icmp packet appropriately for the layer 2 technology
> used on the particular link needed to send the packet along it's way
> to the next hop.
>
> Now, suppose that instead of the packet carrying icmp info, it's
> carrying voice data. Wouldn't the same thing be true?
>
> The answer is YES. Each router along the path will take the ip packet
> carrying voice samples (or call signaling info) and encapsulate it
> with whatever layer 2 headers and trailers are appropriate for the
> type of layer 2 link over which the packet is traveling to it's next
> hop. And, because of this, each hop's layer 2 link technology can be
different.
> The first hop might be ethernet, the 2nd hop could be f/r, the 3rd hop
> could be ATM, the 4th hop could f/r again, the 5th hop could be
> wireless, and so on. You get the idea.
>
> Put simply, when you configue voip, the layer 2 technology is
> transparent to the voip traffic.
>
> Now, this transparency comes at a cost. In addition to the whatever
> headers and trailer are needed for the layer 2 link, the voice packet
> must also have layer 3 headers and trailers and layer 4 headers and
> trailers as appropriate for layer 3 (IP) and layer 4 (usually or
> always UDP). This makes the voice packet bigger which means more
> network resource ( rtr cpu and network
> bandwidth) is needed to transport the voice packets to their
> destinations.
>
> Now, suppose your network looks like this:
>
> phone A --> rtr A --> F/R --> rtr B --> phone B
>
> You have a choice: At rtr A and B you can encapsulate the voice
> traffic in ip and let the network take care of the layer 2 stuff or
> you can save network resources by configuring your rtr's to
> encapsulate the voice traffic directly into frame relay. It's your
> choice (or the choice of those people creating the lab).
>
> The thing to notice is that there's only one hop. Now, voip and VoFR
> aren't mutually exclusive.
>
> Suppose, for example, that rtr 1 is also connected to rtr A by an ATM
> link and that phone 1 is attached to rtr1. When phone 1 wants to call
> phone B, rtr 1 must use voip (because phone B is 2 hops away). Now,
> also assume another phone is attached to rtr B. Let's call that phone B2.
>
> Now, phone A calls phone B and phone 1 calls phone B2. What happens?
>
> At rtr A when the voip traffic arrives from rtr 1, rtr A looks at the
> dest ip addr of the voip packet and sees that this packet needs to go
> to rtr B. So, just like any ip based traffic, rtr A encapsulates the
> voip packet appropriately for the f/r link and sends the packet on it's
way.
> Now, when a voice packet arrives at rtr A from phone A, rtr A because
> it's configured to directly encapsulate voice traffic from phone A
> into f/r, does that.
>
> So, rtr A because there are 2 calls taking place at the same time is
> forwarding both voice traffic streams to rtr B. However, you should
> realize at this point that rtr A doesn't even know that the voip
> traffic from rtr 1 is voip traffic. To rtr A, that traffic is just
> plain old ip traffic and it forwards it just as it would any other ip
> traffic ( except, of course, probably someone has configured QoS so
> that voip traffic doesn't have to wait too long behind FTP traffic or
> other less time critical traffic).
>
> So, based on this example, you can see that voip doesn't "override"
> VoFR or VoATM. They are just different ways of carrying voice traffic.
>
> If you want to really understand this better, I would suggest you read
> a couple of books:
>
> 1) Integrating Voice and Data Networks, Scott Keagy, ISBN 157870-196-1
>
> A truly excellent book which is well written, clear, full of config
> examples and comprehensive.
>
> 2) Cisco Voice over Frame Relay, ATM and IP, Steve McQuerry, ISBN
> 157870-227-5
>
> Not quite as well written as the first book but covers the basics very
> well and includes a number of topics that aren't covered in the first
> book.
>
> 3) DQoS, Wendell Odom
>
> Another truly excellent book. If you're planning on becoming a ccie,
> you have to know the material in this book inside out. And, since QoS
> is critical for voice traffic, you need to understand this broad topic
> very well to properly configure a network to handle voice traffic.
>
> All 3 books are available from Cisco Press.
>
> HTH a bit, Tim
>
>
> ----- Original Message -----
> From: "Yasser Aly" <yasser.aly@noorgroup.net>
> To: "'ccie2be'" <ccie2be@nyc.rr.com>; <trouse@cisco.com>;
> <ccielab@groupstudy.com>
> Sent: Tuesday, July 27, 2004 2:35 AM
> Subject: RE: VOIP over ATM or FR
>
>
> > Hello,
> >
> > Based on your reply it might mean that VOIP overrides Vofr and
> > VoATM
>
> > ? I just need to confirm this or otherwise define when Vofr or VoATM
> > would
> be
> > needed.
> >
> > Thanks,
> > Yasser
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of ccie2be
> > Sent: Monday, July 26, 2004 10:34 PM
> > To: trouse@cisco.com; ccielab@groupstudy.com
> > Subject: Re: VOIP over ATM or FR
> >
> > If you're configuring VOIP, then you don't need to be concerned
> > about Vofr or voATM. The voice traffic flows based on the IP network
> > and doesn't care what the layer 2 link technology is.
> >
> > You still need to configure QoS, but mostly at the L3 level by
> prioritizing
> > precedence 5 packets or their dscp equivalent. How this is done
> > will
> vary
> > depending on the layer 2 technology.
> >
> > HTH a little.
> >
> >
> > ----- Original Message -----
> > From: <trouse@cisco.com>
> > To: <ccielab@groupstudy.com>
> > Sent: Monday, July 26, 2004 11:13 AM
> > Subject: VOIP over ATM or FR
> >
> >
> > > He guys,
> > >
> > > I need some clarification. When configuring VOIP, but traveling
> over a
> > ATM or FR medium, do you still have to address the issues with the
> > L2 technology. IF so what are the key issues for ATM and FR to keep
> > in mind. For example, with ATM do you still have to configure the
> > vbr-rt and COS.
> Do
> > you have to ahve address the fragmenting of data. If a
> question/requirement
> > does not speak of this stuff do you still need to configure it.
> > What is
> the
> > rule of thumb, when the call works and all is pingable but this L2
> > feature and issues are not addressed.
> > >
> > > Thanks Everyone.
> > >
> > > __________________________________________________________________
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-- Jay Greenberg, CCIE #11021http://www.free-tests.com - Free Practice Tests http://www.free-labs.com - Free Router Pods http://www.expert-labs.com - CCIE Router Pods
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