The Internet Protocol (IP) is the main communications protocol of the Internet protocol suit (commonly called the TCP/IP), the networking model that establishes the Internet. A network enables the exchange of information, while a protocol is a set of conventions for formatting communications data. The IP is the method by which data is transferred between computers via the Internet. Thus, its routing system, or system for directing, is what makes the Internet a place for exchanging information.
When data such as a website page or an e-mail is sent via the Internet, the message is divided into packets called “datagrams.” Each datagram is composed of a header and a payload. The header contains the source (sender) and destination (receiver) IP addresses, each of which include the computer's unique network and device addresses, and other metadata needed for routing and delivering the packet. The payload is the message data itself.
The datagram is first sent to a gateway computer—a network point that functions as the entranceway to another network—which reads the destination address and forwards the message to the next gateway. This gateway reads and forwards the address to yet another gateway, and so on, until the message reaches the closest gateway to its destination. The last gateway recognizes the datagram's address as belonging to its domain, or the set of network addresses under its control, and forwards the message directly to the final device destination.
IP routing service is considered unreliable because of the dynamic nature of the Internet and the possibility that any network element may also be unreliable. Therefore, the Internet Protocol has no continuing connection between end points. Each packet of data is treated independently from all other packets of data. Individual datagrams may not necessarily travel the same route across the Internet, as they are trying to get past any errors along the way, and they may arrive in a different order than they were sent. The IP is just a delivery service, so another Internet protocol, the Transmission Control Protocol (TCP), reorganizes the datagrams into their original order.
—Julia Gilstein
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