Gateway (telecommunications)

In telecommunications, the term gateway has the following meaning:

• In a communications network, a network node equipped for interfacing with another network that uses different protocols.
  • A gateway may contain devices such as protocol translators, impedance matching devices, rate converters, fault isolators, or signal translators as necessary to provide system interoperability. It also requires the establishment of mutually acceptable administrative procedures between both networks.
  • A protocol translation/mapping gateway interconnects networks with different network protocol technologies by performing the required protocol conversions.
• Loosely, a computer configured to perform the tasks of a gateway. For a specific case, see default gateway.

Routers exemplify special cases of gateways.

Gateways, also called protocol converters, can operate at any layer of the OSI model. The job of a gateway is much more complex than that of a router or switch. Typically, a gateway must convert one protocol stack into another.

Details

Gateways work on all seven OSI layers . The main job of a gateway is to convert protocols among communications networks. A router by itself transfers, accepts and relays packets only across networks using similar protocols. A gateway on the other hand can accept a packet formatted for one protocol (e.g. AppleTalk) and convert it to a packet formatted for another protocol (e.g. TCP/IP) before forwarding it. A gateway can be implemented in hardware, software or both, but they are usually implemented by software installed within a router. A gateway must understand the protocols used by each network linked into the router. Gateways are slower than bridges, switches and (non-gateway) routers.

A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes, while the nodes that connect the networks in between are gateways. For example, the computers that control traffic between company networks or the computers used by internet service providers (ISPs) to connect users to the internet are gateway nodes.

In the network for an enterprise, a computer server acting as a gateway node is often also acting as a proxy server and a firewall server. A gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the actual path in and out of the gateway for a given packet.

On an IP network, clients should automatically send IP packets with a destination outside a given subnet mask to a network gateway. A subnet mask defines the IP range of a network. For example, if a network has a base IP address of 192.168.0.0 and has a subnet mask of 255.255.255.0, then any data going to an IP address outside of 192.168.0.X will be sent to that network's gateway. While forwarding an IP packet to another network, the gateway might or might not perform Network Address Translation.

A gateway is an essential feature of most routers, although other devices (such as any PC or server) can function as a gateway.

Most computer operating systems use the terms described above. A computer running Microsoft Windows however describes this standard networking feature as Internet Connection Sharing; which will act as a gateway, offering a connection between the Internet and an internal network. Such a system might also act as a DHCP server. Dynamic Host Configuration Protocol (DHCP) is a protocol used by networked devices (clients) to obtain various parameters necessary for the clients to operate in an Internet Protocol (IP) network. By using this protocol, system administration workload greatly decreases, and devices can be added to the network with minimal or no manual configurations.

Internet-to-Orbit Gateway

An Internet-to-Orbit gateway (I2O) is a machine that acts as a connector between computers or devices connected to the Internet and computer systems orbiting the earth, like satellites or even manned spacecrafts. Such connection is made when the I2O establishes an stable link between the spacecraft and a computer or a network of computers on the Internet, such link can be control signals, audio frequency, or even visible spectrum signals.

Project HERMES is the first of this kind of devices to become operative. The HERMES-A/MINOTAUR Space Flight Control Center became operative on June 6 2009 and was operated by representatives of 34 countries on the UNOOSA Symposium of Small Satellites for Sustainable Development in Graz, Austria on September 10, 2009. Project HERMES is an initiative of the Ecuadorian Civilian Space Agency and has a maximum coverage of 6,000 km, HERMES-A is supposed to be the first gateway of a network of five covering all south america. HERMES-A/MINOTAUR is not only capable of data transmission but voice also.

Project GENSO is an initiative from NASA and ESA, and it is expected to begin operations on April 2010, it is supposed to have worldwide coverage.

Examples

• A very popular example is connecting a Local Area Network or Wireless LAN to the Internet or other Wide Area Network. In this case the gateway connects a LAN to the provider-specific network which in turn connects to the Internet. In the case of a home, this gateway is called a residential gateway.
• MainWay is the Bull brand for a gateway which connects DSA to TCP/IP telecom

Sources

• Federal Standard 1037C
• MIL-STD-188

See also

• Router
• Subnet