VoIP Gateway is a device that allows telephone calls to be transmitted over Internet Protocol (IP) backbone networks by converting voice signals into IP packets and transmitting them over the network. The reverse process takes place at the other end of the call.
Most VoIP gateways are chassis-based units that have either digital or analog built-in Private Branch Exchange (PBX) interfaces. A gatekeeper keeps track of IP address to phone number mappings for routing calls between gateways. Built-in local area network (LAN) and/or wide area network (WAN) interfaces are included for connecting the gateway to the IP backbone. Some gateways also have built-in routing capabilities. The LAN interface is usually Ethernet, but some gateways support Token Ring. The WAN interface is typically T1 or E1, but smaller gateways designed for small office/home office (SOHO) environments support Integrated Services Digital Network (ISDN) interfaces. The number of voice interfaces per chassis typically ranges from 72 to 960, depending on the vendor. Voice interfaces are typically the digital signal cross-connect level (DSX-1) type, but some gateways also support the foreign exchange station (FXS) type interfaces for direct attachment of analog telephones.
When you shop for a VoIP gateway, you should consider the following:
Graphic V-4. VoIP gateway.