Considering 100Mbps ethernet only uses 4 of the 8 wires, using cat 3 wiring is pheasable. It all depends on the quality of the cable.


Preston Garrison direct: 877-748-4142 fax: 310-774-3901 cell: 623-748-4140

-----Original Message-----
From: steve szmidt <[EMAIL PROTECTED]>
To: Commercial and Business-Oriented Asterisk Discussion <[email protected]>
Sent: Sun, 27 Mar 2005 16:34:42 -0500
Subject: Re: [Asterisk-biz] Forklift a 2000 phone PBX


On Sunday 27 March 2005 15:14, Reid Forrest wrote:
> This seems like a really bad idea. Why lock down into a not only
old and
> outdated technology, but for 2000 users?!!
>
> You want to keep the network operating efficiently. Modern switches
does
> a lot
> better job than yesterdays technology. If you have 250 people on the
> phone at
> the same time, and you are using g.729, you have used 10Mb right
there.
> Never
> mind any other protocol.

Steve, I agree with you that trying to run voice over Cat3 is not the
best
idea. But, I think your math may be off in the calculation above. 250
people on the phone using g.729, even compensating for protocol
overhead of
25% is only 2.5Mbit/sec.

Sorry but we are not talking about a one way conversation. It requires shy of
20K for a two way conversation.


In addition, you are assuming that the voice
network is completely FLAT, not switched. A fully switched voice
network
would reduce bandwidth consumption at every station.

No it doesn't. Switched does not lower the needs of a g.729 connection. The
only savings are in not having collisions, and retransmissions, as with a
hub.


A 2000 user switched
voice network over Cat3 is viable, as long as you keep data off of it.

Well, it turned out that he has Cat 3 from the previous phone system available, and that is what he is talking about. I missed that point.

As for a dedicated Cat 3 to run a voice leg to a switch that would obviously
be fully workable. However, if you were to integrate it to a 100Mb network
then it will switch down the 100 for each 10 packet entering that leg. Of
course that might still be faster than running a 10Mb network.


--

Steve Szmidt

"They that would give up essential liberty for temporary safety
deserve neither liberty nor safety."
                               Benjamin Franklin
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