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Microsoft® Office Communications Server 2007 Resource Kit by Microsoft OCS Team, Stephanie Lindsey, Rick Kingslan, Mitch Tulloch, Kintan Brahmbhatt, John Clarkson, James O'Neil, Hao Yan, Byron Spurlock, Jochen Kunert, Rui Maximo, Jeremy Buch

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Bridging VoIP to the PSTN Network by Using a Media Gateway

For voice calls from Office Communications Server 2007 to reach the Public Switched Telephone Network (PSTN), a third-party media gateway is required to bridge the IP network and the PSTN network by translating the signaling and media to the protocols used by each network, as shown in Table 3-2.

Table 3-2. Protocol Translation Performed by Media Gateway

Technology

PSTN Network

IP Network

Signaling protocol

SS7 and others

SIP

Media codecs

G.711

RTAudio

Transport Protocol

T-Carrier/E-Carrier

RTP (Real-Time Protocol)/SRTP (Secure RTP)

Network Type

Circuit switched

Packet-based

Such a media gateway is provided by Microsoft partners. (See the Additional Resources section at the end of this chapter for the link.) ...

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