For nodes to exchange data, they must use a common set of rules defining the format of the data and the method in which to transmit it. A protocol is a formalized rule set regarding the exchange of data and the interactions between the network nodes. A router connects networks only if they are using the same protocol and formats. To communicate between networks with differing protocols and address formats a gateway is needed. The gateway converts addresses and protocols to connect dissimilar networks.
Networks connected by routers or gateways are known as an internet. For this reason the term ‘Internet’ (capitalised) is used to refer to the largest global system of networks, also called the Worldwide Internet. The basic protocol for implementation of the Worldwide Internet is called the Internet Protocol (IP).
