TDM over VoIP

[worldcalltel]

what is TDM over VoIP? what does it do compare to traditional VoIP?

[fred.s.mollenkopf]

Rick,

I could be wrong on this terminology but I've always equated that to clear channel signaling over IP. This might not be the exact term but it's an example of TDM over VoIP. Essentially the VoIP backbone is routing the traffic not on a call-by-call basis but to a predetermined route, ex. T1 to T1. Here is a document.

http://www.cisco.com/en/US/tech/tk652/tk653/technologies_tech_note09186a00800a96c1.shtml

Please rate any helpful posts

Thanks

Fred

[pacameron]

TDMoIP means you take a conventional TDM bit stream, eg T1 or E1 CAS/PRI or ISDN BRI and pass it over an IP network.

There is a lot of good information here -

http://www.tdmoip.com/Home/0,,5,00.html

http://www.tdmoip.com/Article/0,6583,26459,00.html

The benefits of TDMoIP is that you can integrate legacy TDM networks (such as PBX's, telephony systems, channelised transmission systems, encrypted bit streams) into IP networks.

All good in theory, the gotchas are that you need the IP network to be very reliable (every bit counts in TDM systems!) and very low latency (TDM has no real concept of delay and extra delay may cause issues such as echo on voice calls that were never apparent on the original TDM system)

Cisco have a similar product called Circuit Emulation Over IP (CEoIP) for E1, T1 and serial interfaces -

http://www.cisco.com/en/US/products/ps5854/products_data_sheet09186a00802045f5.html

In terms of advantages over VOIP - you keep your existing equipment rather than use voice cards and DSP's on the router to handle the voice calls. You still need the TDMoIP or CEoIP boxes though.