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Home > Resources > Technical Resources > Black Box Explains > WAN > Time-Division Multiplexing over Internet Protocol (TDMoIP).
Time-Division Multiplexing over Internet Protocol (TDMoIP).

Time-Division Multiplexing over Internet Protocol (TDMoIP)

Time-Division Multiplexing over Internet Protocol (TDMoIP) is a transport technology that extends traditional voice, data, and video applications transparently over IP or Ethernet network infrastructures.

For voice applications, TDMoIP supports legacy PBXs (including proprietary features), plus it supports any signalling (including ISDN, Q.SIG, and SS7) as well as all modem and fax rates. TDMoIP also supports many data communication protocols—ATM, Frame Relay, HDLC, ISDN, SNA, SS7, sync/async, and X.25. For video transfer, TDMoIP supports the H.320 (PRI) and H.324 (BRI) services.

In addition to its versatility, TDMoIP is also simpler and less expensive than Voice over IP (VoIP). In short, TDMoIP is ideal for enterprise and carrier applications.

How TDMoIP works
Gateways for TDMoIP, such as the Multi-Input IP Muxes, first receive a data stream at their T1/E1 or analogue voice interfaces. There the stream is chopped into fixed-size packets and given an IP header. Next the packets are forwarded over the IP network to the gateway on the receiving end. The receiving gateway then reconstructs the original data stream by removing the IP header, concatenating the packets, and regenerating the clock. The stream is then forwarded to its destination where it is delivered on the standard T1/E1 or analogue voice interface.

TDMoIP and VoIP both deliver convergence, which is the combining of two or more disparate disciplines or technologies (like sending voice and data onto a single network). But there are differences that give TDMoIP the edge.

TDMoIP uses standard, established technologies like T1 and IP. VoIP revolves around new and evolving protocols such as H.323, MGCP, and SIP. By the time an IT staff learns one group of protocols, more money has to be shelled out so the staff can learn the next batch of “alphabet soup“ rules.

TDMoIP enables you to use your existing PBX units, whereas VoIP will likely require the expense of upgrading all your PBXs and cause disruption to your business. And because TDMoIP is transparent to signalling and protocols, you don’t have to deal with translation time between signalling formats as you would with VoIP.

With TDMoIP, packet sizes are configurable. VoIP packet sizes, on the other hand, depend on codec samples—and there are yet more delays as each sample is recorded. This adds overhead to each voice session.

TDMoIP and VoIP both deliver convergence to reduce administration, cabling, and hardware costs. However, VoIP remains complex for voice switching applications, whereas TDMoIP has much broader appeal because it transports any TDM-based voice, video, or data over IP for the ultimate investment protection. Now that’s saving money!

The bottom line
Now that you know what TDMoIP is, consider the savings offered by TDMoIP gateways. Their capability to emulate T1 or E1 circuits over IP makes it possible for your enterprise to protect its investment in legacy equipment and avoid costly upgrades. Plus, expensive T1 or E1 circuits can be eliminated as your network migrates to IP.

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