Introduction to AVVID Gateways
A gateway, by definition, is a device that converts one media or protocol to
another. In the AVVID or Voice over IP (VoIP) environment, a gateway is responsible
for connecting an IP telephone network to the PSTN or PBX and key systems.
For example, the gateway may connect an H.323 network to an SIP-based
network, PSTN, or ISDN. It also performs translations between different transmission
formats and communication procedures, and is responsible for setting up
and clearing calls on both sides. Communication between terminals and gateways
is done through the H.245 and Q.931 protocols.
Types of gateways range from specialized entry-level standalone devices to
enterprise-level integrated router and switch gateways. Based on the device or
the implementation, the gateways communicate with Cisco CallManager or
other network devices over various gateway protocols.Your own infrastructure
and VoIP requirements will help determine what gateway is right for you, but
required common features include: DTMF relay, CallManager redundancy, and
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supplementary services. Supplementary services allow users to perform call hold,
transfer, and conferencing.
AVVID gateways themselves are in the form of analog and digital versions
running different protocols, each of which we’ll cover in the coming sections.