Communications protocol

Main article: Communications protocol

A communications protocol defines the formats and rules for exchanging information via a network and typically comprises a complete protocol suite which describes the protocols used at various usage levels. An interesting feature of communications protocols is that they may be – and in fact very often are – stacked above each other, which means that one is used to carry the other. The example for this is HTTP running over TCP over IP over IEEE 802.11, where the second and third are members of the Internet Protocol Suite, while the last is a member of the Ethernet protocol suite. This is the stacking which exists between the wireless router and the home user's personal computer when surfing the World Wide Web.
Communication protocols have themselves various properties, such as whether they are connection-oriented versus connectionless, whether they use circuit mode or packet switching, or whether they use hierarchical or flat addressing.
There exist a multitude of communication protocols, a few of which are described below.