The Internet utilises packet switching to traffic data across the interconnected computer networks of the Internet. Computer networks that use packet switching are comprised of physical devices (switches) that forward blocks of data (packets) from a source location to a destination location.
How data packets are formatted and routed on the Internet is determined by the protocols of the Internet protocol suite. The core protocols of the Internet protocol suite are TCP and IP. When a network is connected to the Internet it is given an IP address. This is a 32 bit number, defined by the Internet Protocol (IP), and assigned to the network by the Internet Assigned Numbers Authority (IANA) and Regional Internet Registries (RIR).
When a network on the Internet wants to send data to another network it uses the Internet Protocol (IP) to format the data into packets, and the Internet Protocol (IP) creates a packet header that provides addressing information. The Internet Protocol (IP) is sometimes defined as a routed protocol: it provides routing information, whereas routing protocols decide how to route the data packet.
Networks connected to the Internet use a device named a gateway/router to send data packets to another network. The Internet's network architecture - host computers using routers - was pioneered by the ARPANET computer network (forerunner to the Internet). Since the creation of ARPANET there has been many types of routing protocols. In the 1980's, the NSFNET computer network used the following routing protocols: ANSI IS-IS; ISO ES-IS; Hello; Gateway Gateway Protocol (GGP); and Routing Information Protocol (RIP).
Presently, the gateways/routers of the Internet use a range of
external and internal routing protocols. Some example of external
routing protocols are: Exterior Gateway Protocol (EGP) and Border
Gateway Protocol (BGP). Some example of internal routing protocols
are: Routing Information Protocol (RIP); Intermediate System to
Intermediate System (IS-IS) and Open Shortest Path First (OSPF).