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Collaboration, Voice & AV · Foundational

Voice Gateway

A device that converts between IP telephony signaling and media and TDM or analog interfaces such as PRI, FXO and FXS.

Definition

Voice gateways translate between protocols like SIP, H.323 or MGCP on the IP side and ISDN, CAS or analog signaling on the TDM side, while DSPs convert PCM to RTP. Cisco ISR routers and VG series analog gateways are common examples. A gateway's protocol choice affects where the dial plan lives and how survivability works.

Example

A Cisco VG420 provides 48 FXS ports for analog phones and fax machines in a warehouse.

Exam tip

Compare gateway protocols: SIP and H.323 are peer-to-peer with local dial peers, MGCP is centrally controlled by CUCM.

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