G7xx
Gatekeeper
Gateway

G.7xx
A family of ITU standards for audio compression. [+info]

Gatekeeper
The central control entity that performs management functions in a Voice and Fax over IP network and for multimedia applications such as video conferencing. Gatekeepers provide intelligence for the network, including address resolution, authorization, and authentication services, the logging of CDRs, and communications with network management systems. Gatekeepers control bandwidth, provide interfaces to existing legacy systems, and monitor the network for engineering purposes as well as for real-time network management and load balancing.

Gateway
In IP telephony, a network device that converts voice and fax calls, in real time, between the public switched telephone network (PSTN) and an IP network. The primary functions of an IP gateway include voice and fax compression/ decompression, packetization , call routing, and control signaling. Additional features may include interfaces to external controllers, billing systems, and network management systems.