PSTN Gateway and IP PBX Interoperability

For IP-based real-time applications that must communicate with a PSTN network on one side and a unified communications network on the other side, Microsoft Unified Communications Managed API (UCMA) 3.0 provides an application the ability to interoperate with SIP PSTN gateways and IP-PBXs with the unified communications network.

The following SIP peers can connect to the UCMA application.

  1. SIP gateways.

  2. SIP-enabled IP-PBXs that support the following phones.

    1. SIP phones

    2. Soft phones that support SIP

SIP peers should support the following protocols.

  • SIP—RFC 3261

  • DTMF—RFC4733

  • SDP—RFC 3264

In addition, SIP peers:

  • Must provide media session parameter negotiation (endpoint, codec, and, if applicable, encryption parameters) through SDP, as defined in the SIP and related RFCs and used in SIP.

  • Must provide media/audio transport using RTP/RTCP over UDP.

  • Must meet the Supported IP Gateways requirements listed in Telephony Advisor for Exchange 2010.

The following illustration shows a typical setup.

IP-PBX Gateway

For more information, see Trusted Domains and SIP Gateways.