Difference between Softswitch and IP PBX?

There is lot of difference between the normal TDM PSTN switch and the normal PBX. But the difference between IP PBX and the softswitch is very narrow.. Other than the subscriber capacity and the call handling capacity what are the main difference between softswitch and a IP PBX? Is IP PBX can be connected to a third party application server? Please give me some inputs....

1 Answer

  • 1 decade ago
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    You're starting off with a couple of assumptions with which I do not agree. The major difference between a carrier-class CO switch and a PBX is exactly as implied by the name: a private branch exchange is designed for a single private branch - i.e. a much, much smaller installation than a CO switch like a 5Ess or DMS500. Functionally, a PBX has essentially the same capabilities as a CO switch.

    Similarly, a PBX that can handle VoIP has essentially the same capabilities as a softswitch.

    In both cases, differences are scale and NNI (network-network interface) capabilities. A softswitch designed for carrier use (e.g. by a CLEC) must be able to handle number porting and interface with the inter-carrier database. A VoIP or more typically a hybrid VoIP and TDM PBX (like a Mitel 3300 ICP for example) need not (and does not) have those capabilities, but it does have embedded voice mail, multiple tenant groups, and dozens of other functions that are designed for applications closer to the last mile (or last 20 feet), that the CO switches generally don't have, or have only in more limited flavors.

    Yes, a VoIP or hybrid PBX can be connected to an application server. If it talks SIP it can also interface directly to a LEC's softswitch. The good ones (Mitel, Alcatel-Lucent, Cisco among others) provide APIs for manipulating the voice channels and interacting with external servers.

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