[Asterisk-biz] Forklift a 2000 phone PBX

[Preston Garrison]

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 <steve at szmidt.org>
To: Commercial and Business-Oriented Asterisk Discussion 
<asterisk-biz at lists.digium.com>
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 outdated technology, but for 2000 users?!!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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