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New Member

Sizing voip systems

We have a client who purchased a 7750 with 150 Phones, they would like to expand the system by another 700 phones. I cannot find a tool to calculated the required DSP etc, we have 3524s with inline power, but there must be a limit. I would like to install a 6500 with voice card as the other site has 4 E1 connections. Has anyone had experience of these type of sites, I could put in 3 6500 with everything but I think the client would have a problem with costs.


Re: Sizing voip systems

I can't find any specific tool to calculate the number of DSPs required. It would all depend on number conferences and transcoding services that you want to provide at the same time.

New Member

Re: Sizing voip systems

First, the 7750 isn't designed to support that many devices. You'd probably want to move them to the 7835 platform. As for DSP resources, you could use VG200's with HDV modules with the proper DSP resource module on them. There's also a DSP-FARM module if you need transcoding resources, etcetera. That should be better on their budget.

Re: Sizing voip systems

I agree with the commentabout the ISC 7750 not going that big, but the DSPs should be quite easy.

You don't need any if everything runs G.711, so that's not a problem. Then you should look at intersite traffic, which I assume will use G.729. In this case you need to be able to transcode the G.729 to G.711 to allow them to conference.

My advice would be use the spare 6608 ports on 1 site to provide 1 set of transcoding and 3 of conference, this should be more than enough. On the other site you are going to require a VG-200 with the DSp-farm module to provide you with the same services.

really without knowing the number of extensions on both sites it's difficult to say, but if you have a 6K switch on both sites then the 6608 is by far the most cost effective way to do almost anything.

A single 6500 core with 3524-pwrs at the edge is the favoured way of implementing telephony (unless you have money to through at it (waste?) with 6Ks everywhere).


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