A Media Gateway is a hardware/software device that functions as a ‘gate’ between two networks. Media Gateways are network nodes that interface with other networks often using different protocols. A gateway device could be a router, firewall, server, or any device that enables traffic to flow in and out of the network.

While a media gateway is a node itself, it also functions to protect other nodes within a network. It is able to do this because all data flows through the gateway node before entering or exiting a network. Media Gateway nodes also translate data received from outside networks into a format, or protocol, that is recognizable to devices in the internal network. For this reason gateways are also sometimes referred to as protocol converters. Media Gateways do not impact the payload content, only the protocol wrapper.

The computers of all Internet users as well as the computers that serve web pages to users are known as host nodes. Media Gateways, then, are the nodes that connect the networks in between host nodes. Computers that control traffic between company networks and computers that internet service providers (ISPs) utilize to connect users to the Internet are both examples of gateway nodes.