In information and communication technology, gateways are able to translate or transform protocols, allowing different applications or networks to communicate. For example, a gateway can translate the IPX/SPX protocol by Novell into Internet Protocol or vice versa. Information may possibly also be lost in the process if not equally supported or transportable by the different protocols. Another example of a gateway is a system which translates e-mails into SMS and vice versa. Gateways are enabled on all seven layers or only individual layers of the OSI seven layer model. In addition to protocol conversion gateways, there also are gateways which convert different types of media. Gateways are often used to bridge different networks.
A gateway can establish a connection between a circuit-switched network such as an ISDN network and a packet-switched network such as the IP network. The so-called VoIP gateway is a device or a system which bridges the classic analogue or digital telephone and IP telephony. This type of gateway can for example be used to connect a conventional Telephone system to your ISDN interface. The gateway converts the ISDN protocol to Session Initiation Protocol (SIP) and transmits the signals using the IP interface. This function allows for soft migration into the world of IP telephony. The existing telephone system can easily be used with a new IP-based connection and later replaced with an IP-capable system. When utilizing the services of a cloud telephone system, the conventional system can be used until cloud telephony is implemented and then disconnected. To ensure the smoothest possible migration to IP telephony, many internet access routers already feature extensive VoIP gateway functions. Existing telephone systems or telephones can be connected directly to these routers and still be used.