Gateway

A gateway is exactly what its name suggests — a gate. It is the key access point that connects an organisation’s internal network to the outside world, most commonly the Internet. Every piece of data that enters or leaves the network must first pass through the gateway. This makes the gateway both the entry and the exit point of a network.

The gateway does more than just let traffic in and out. It also handles routing: it decides the best path for data packets to travel. To do this, the gateway maintains two kinds of information — details about the host network’s own internal connection paths, and information about the identified paths of other remote networks.

When a node (say, a computer) on one network wants to communicate with a node on a foreign network, it sends the data packet to the gateway. The gateway then routes that packet to the destination using the best possible route it knows.

In most computer networks, a router is configured to work as a gateway device. However, a gateway is not limited to hardware alone. It can be implemented in three ways:

• Software only — the gateway logic runs as a program on a general-purpose computer.
• Hardware only — a dedicated physical device (like a router) serves as the gateway.
• A combination of both — software running on specialised hardware. …