The most notable example of internetworking is the Internet (capitalized), a network of networks based on many underlying hardware technologies, but unified by an internetworking protocol standard, called the Internet Protocol Suite (TCP/IP).
The network elements used to connect individual networks are known as routers, but were originally called gateways, a term that was deprecated in this context, due to confusion with functionally different devices using the same name.
The interconnection of networks with bridges (link-layer devices) is sometimes incorrectly termed "internetworking", but the resulting system is simply a larger, single subnetwork, and no internetworking protocol (such as IP) is required to traverse it. However, a single computer network may be converted into an internetwork by dividing the network into segments and then adding routers between the segments.
The original term for an internetwork was catenet. Internetworking started as a way to connect disparate types of networking technology, but it became widespread through the developing need to connect two or more local area networks via some sort of wide area network. The definition now includes the connection of other types of computer networks such as personal area networks.
IP only provides an unreliable (i.e., not guaranteed) packet service across an internet. To transfer data reliably, applications must utilize a Transport Layer protocol, such as Transmission Control Protocol (TCP), which provides a reliable stream. Some applications use a simpler transport protocol, User Datagram Protocol (UDP) for tasks which do not require reliable delivery of data or that require real-time service, such as video streaming.
The Internet Protocol Suite, also called the TCP/IP model, of the Internet was not designed to conform to this model and does not refer to it in any of the normative specifications (Requests for Comment) and Internet standards. Despite similar appearance as a layered model, it uses a much less rigorous, loosely defined architecture that concerns itself only with the higher level aspects of networking, i.e. it does not discuss hardware-specific low-level interfaces, other than assuming availability of a link-layer interface to the local network link. Internetworking is facilitated by the protocols of its Internet Layer.