Priscilla wrote:
> I have gotten quite a few of these simple voice/data
> networks up and running. It's very easy. There is no Call
> Manager! And, as you mentioned, the major benefit is that
> you bypass long-distance charges because you simply use
> the existing data network. You may need to prioritize
> voice, and break up big data packets to get the low level
> of delay required for voice, but other than that, there's
> not much to it
For many purposes there's not much for the network
administrator to do, as you mention. In other contexts
such as a company that has a bunch of expensive PBXs that
have to be integrated onto the WAN portion of the data
network, one must exercise care to benefit from bypassing
PSTN and other legacy solutions.
Later steps can be taken to evolve to the full AVVID
solution discussed in the CIPT book, but for now I have to
focus on the Cvoice model, namely, using VoFR, VoATM and
VoIP to stop the hemorrhage of funds into legacy
long-distance voice networking. Getting those PBXs talking
to each other over an FR or ATM cloud is no small matter,
and the economic benefit is huge.
-- TT
-------- Original Message --------
Subject: RE: CVOICE book: VoATM and VoFR [7:53567]
Date: 19 Sep 2002 00:29:26 -0000
From: [EMAIL PROTECTED] ("Priscilla Oppenheimer")
Organization: GroupStudy.com Discussion Groups
Newsgroups: groupstudy.cisco
Tom Scott wrote:
>
> Having asked about VoMPLS transcoding from analog voice to MPLS
> frames without intermediate IP packets, my lab partner noticed
> that the CVOICE book (edited by Steve McQuerry etal) discusses
> VoFR and VoATM (chapters 8 and 9):
>
>
> analog +-------+ +-------+ analog
> phone A1 ---- | | ATM | | ---- phone B1
> ... | rtr A | ---- or FR ---- | rtr B | ...
> analog ---- | | cloud | | ---- analog
> phone Ai +-------+ +-------+ phone Bj
>
>
> Are we reading this correctly, that the analog phones plug into
> the cisco routers and the analog voice traffic is transformed
> into FR frames or ATM cells, with no IP packets in between?
> It makes sense to do it that way in some applications. For
> example, if you have a call center in a distant suburb across
> a LATA line or two, that services a metropolitan area, then
> you'd want to bypass long-distance charges if at all possible.
>
> This seems like an easy way to do it. But what handles the
> call control? Does the router do that? Some of the diagrams
> in the CVOICE book have no PBX (or CCM) in them. Does the
> router translate the call-control signaling from the analog
> phone into corresponding pass-through signaling in the ATM/FR
> packets (sort of like user-to-user signaling that could be
> passed through SS7, in this case the users are the routers
> and the network is the ATM/FR switches)?
Yup, you got it, although it may be even simpler than you imagine.
Before AVVID, Cisco did VoIP, VoFR, and VoATM, as discussed in the CVOICE
class. With these solutions, you simply connected analog phones to FXS ports
on routers. The routers digitized and compressed the dialed digits and the
voice itself and packetized it. If it was VoATM or VoFR, there was no IP.
The data was simply put into data-link-layer frames (or cells with ATM).
You asked about the call-control signaling from the analog phone, but how
much would there be? These phones would be your basic $5.99 KMart special
with no bells and whistles, so to speak. The router provides dial tone and
picks up the dialed digits and forwards them to the other router.
As you can probably tell, I'm not a telepony expert, but I have gotten quite
a few of these simple voice/data networks up and running. It's very easy.
There is no Call Manager! And, as you mentioned, the major benefit is that
you bypass long-distance charges because you simply use the existing data
network. You may need to prioritize voice, and break up big data packets to
get the low level of delay required for voice, but other than that, there's
not much to it. The original CVOICE class covered only these types of
solutions and I'm sure the book still has a lot of this flavor, although
both the book and the newer version of CVOICE also cover newer solutions too
these days probably.
_______________________________
Priscilla Oppenheimer
www.troubleshootingnetworks.com
www.priscilla.com
>
> -- TT
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=53909&t=53909
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