What is a networking gateway?

From networking point of view Gateway is a device which provides connectivity between two heterogeneous networks/systems to communicate. This is done using protocol translation. Gateway embeds both protocols of different systems in order to provide interoperability functions. Gateway can provide interconnectivity between more than two different systems also.

There are various gateways designed as per the need of different systems/technologies. These include GSM/CDMA gateway for VOIP, T1(1.544Mbps)/E1(2.048Mbps) gateway, access gateway, GMSC and more.