Internet Protocol

The Internet Protocol is a protocol used for communicating data across a packet-switched internetwork using the Internet Protocol Suite, also referred to as TCP/IP. IP is the primary protocol in the Internet Layer of the Internet Protocol Suite, and has the task of delivering distinguished protocol datagrams (packets) from the source host to the destination host solely based on their addresses. For this purpose, the Internet Protocol defines addressing methods and structures for datagram encapsulation. The first major version of addressing structure, now referred to as Internet Protocol Version 4, is still the dominant protocol of the Internet, although the successor, Internet Protocol Version 6 is being deployed actively worldwide.

The Internet Protocol is responsible for addressing hosts and routing datagrams (packets) from a source host to the destination host across one or more IP networks. For this purpose the Internet Protocol defines an addressing system that has two functions. Addresses identify hosts and provide a logical location service. Each packet is tagged with a header that contains the meta-data for the purpose of delivery. This process of tagging is also called encapsulation. IP is a connectionless protocol and does not need circuit setup prior to transmission.

The design principles of the Internet protocols assume that the network infrastructure is inherently unreliable at any single network element or transmission medium, and that it is dynamic in terms of availability of links and nodes. No central monitoring or performance measurement facility exists that tracks or maintains the state of the network. For the benefit of reducing network complexity, the intelligence in the network is purposely located in the end nodes of each data transmission. Routers in the transmission path forward packets to the next known local gateway matching the routing prefix for the destination address. As a consequence of this design, the internet protocol only provides best effort delivery and its service can also be characterized as unreliable. It is a connectionless protocol, and the lack of reliability can allow any one of the following fault events to occur: data corruption, lost data packets, duplicate arrival, and out of order packet delivery. Internet Protocol Version 6 has abandoned the use of IP header checksums for the benefit of rapid forwarding through routing elements in the network.

IP Addressing refers to how end hosts become assigned IP addresses and how subnetworks of IP host addresses are divided and grouped together. Internetwork routers use either interior gateway protocols, which perform IP routing by all hosts, or external gateway protocols, which help make IP datagram forwarding decisions across IP connected networks.