Cisco IPT VoIP

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Oct 18th, 2008
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I am trying to implement a Cisco VoIP (IPT) solution for a company with three sites (Nigeria, Ghana and Kenya). How possible is it to implement this solution through the internet and what challenges am I likely to face. Will a Callmanager express solution be okay for this. Please advice.

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Md. Mijanur Rahman Sun, 10/19/2008 - 02:11
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You will need three voice gateways of your preferred model (depends on capacity) at each of the three locations. You can set real IP at their interfaces, but this is not recommended for security issues, rather than you should use vpn tunnel with each other.

Yes, you can use CallManager express for single site voip solution for scenarios like you. You will must not register your remote IP phones to a remote sided CME, implement CME at each location.

>>what challenges am I likely to face

Ensure your BW availibility and performance.

Hope this help.

peternnaji Sun, 10/19/2008 - 08:57
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Thanks a lot for your response. I actually wanted to be sure this can be done over the internet. One more thing; how does Bandwidth come into play since the voice packets has to be traversed over the internet and not a dedicated WAN? And what is the minimum bandwidth required for effective communication for the three locations?

Md. Mijanur Rahman Mon, 10/20/2008 - 05:14
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Bandwidth requirement rely on your number of simultaneous calls, reserve 24kbps bandwidth at G729 codec per call for best performance.

If you expect 5 simultaneous calls will be running between two sites, reserve 24*5=120kbps between them.

Hope this help.

Chris Deren Mon, 10/20/2008 - 05:39
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Actaully G729 payload is 24kbps, but you need to add an overhead. Depending on L2 media the overhead is different, for Internet connection you will probably need 32kbps or so, also if you are going to encapsulate these into VPN there is encapsulation overhead as well.

Running voice over public internet is never advised as you have no control over QoS, not to say it won't work as for the most part it should be OK, however if will on occasions run into packet drops, latency, jitter, etc.



mikram Mon, 10/20/2008 - 05:44
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I have customer who has similar scenarios, voip over Internet. We deployed DMVPN as it seems to be working fine. Have look at DMVPN implementation.

Good Luck



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