The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet runs.
A protocol is a mutually agreed-upon format for doing something. With regard to computers, it most commonly refers a set of rules (i.e., a standard) that enables computers to connect and transmit data to one another; this is also called a communications protocol. A protocol can be implemented by hardware, software, or a combination of the two.
A protocol stack is a complete set of protocol layers that work together to provide networking capabilities. It is called a stack because it is typically designed as a hierarchy of layers, each supporting the one above it and using those below it. Each layer solves a specific set of problems involving the transmission of data and provides well-defined services to the layers above it. Higher layers are logically closer to the the application programs and deal with more abstract data, and they rely on lower layers to convert their data into forms that can be physically manipulated for transmission.
The Internet protocol suite is sometimes called the TCP/IP protocol suite, after TCP/IP, which refers to the two most important protocols in it: the transmission control protocol (TCP) and the Internet protocol (IP). These were also the first two protocols in the suite to be developed.
This suite has five layers, in contrast with the seven layers of the OSI (open systems interconnect) reference model, each of which contains a number of protocols. Among the main ones are HTTP (hypertext transfer protocol), FTP (file transfer protocol), SSH (secure shell), Telnet and BitTorrent at the application layer, TCP and UDP (user datagram protocol) at the transport layer, IP at the network layer, Ethernet, FDDI (fiber distributed data interface) and PPP (point-to-point protocol) at the data link layer, and 10Base-T, 100Base-T and DSL (digital subscriber line) at the physical layer.
The Internet protocol suite can be described by analogy with the OSI model, although there are some major differences and not all of the layers correspond well with their counterparts. In particular, the Internet protocol suite model was produced as the solution to a practical engineering problem, whereas the OSI model is a more theoretical approach and was developed at an earlier stage in the evolution of networks.
Created October 31, 2005.