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Community Member

IP Design

I have a couple of question.

1st I have a central site connected to about 5 remote sites with full t1's with about 40 users at each remote site.

I have seen places where cisco recomends that if the remote site has over 20 phones install a call manager there, but then I see the 3660 can support 144 phones in SRST. So is it safe to install a central site system and install 3640's (they support 48 phones)at the remote branch's?

Also if we install a PRI in each 3640 and use it as a h.323 gateway, how much bandwith will I use? For example if i use g729 will i use 15 to 20 k of the t1 line to the central site even if the call goes out of the local gateway?

Thanks in advance

Cisco Employee

Re: IP Design

I am not in Marketing and those are the folks that make up the numbers for design recommendations. I have heard that we recommned a ccm for sites with 25 users or more. I guess the decision is up to you whether to got with the central site model or the distributed model. I will try and help with your other question. If you are not using header compression than g.729 will take up about 24k a call. If you are calling from and IP phone at the remote site to the pstn through a gateway at the remote site. The only bandwidth taken up will be the bandwith to setup the call. The rtp(audio) will be between the IP phone at the remote site and the gateway at the remote site. The only exception is if you are using some resource at the central site. A conference bridge is a good example. If you are doing conferencing. Then the rtp would traverse the WAN.

Hope this helps,


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