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Internet Protocol

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The Internet Protocol, commonly known as IP, is a fundamental communications protocol. It operates at the network layer of the Internet protocol suite. Its primary purpose is to relay datagrams across various network boundaries. This routing function enables internetworking, which essentially establishes the Internet itself. IP handles the delivery of packets from a source host to a destination host. It does this solely by using the IP addresses found in packet headers.

TCP and IP protocols development timeline-en
TCP and IP protocols development timeline-en

To move information, IP uses a process called encapsulation. This involves nesting a data payload inside a packet structure. Each datagram consists of two distinct components: a header and a payload. The payload contains the actual data being transported. The header contains the source IP address and the destination IP address. It also includes other metadata required to route and deliver the datagram.

UDP encapsulation
UDP encapsulation

This header acts as a set of instructions for the network.

IP routing is a task performed by both individual hosts and specialized devices called routers. Routers function to transport packets across different network boundaries. These routers communicate with each other using specific routing protocols. These protocols are categorized as either interior gateway protocols or exterior gateway protocols. The specific type used depends on the topology of the network. The address space itself is divided into smaller sections called subnets. This process involves the designation of specific network prefixes.

The history of IP began with the work of Vint Cerf and Bob Kahn. In May 1974, they published a paper titled "A Protocol for Packet Network Intercommunication." This paper described a method for sharing resources using packet switching. Originally, they developed a monolithic Transmission Control Program. This program included both connection-oriented links and datagram services. Later, this was divided into a modular architecture. This modular system became known as the TCP/IP suite.

First Internet Demonstration, 1977
First Internet Demonstration, 1977

A major demonstration occurred on November 22, 1977, linking networks like ARPANET and SATNET.

There have been several versions of the Internet Protocol. Internet Protocol version 4, or IPv4, is currently the dominant version. It uses 32-bit addresses, which allows for approximately 4.3 billion unique addresses. Because the number of devices grew, a successor was needed. This successor is Internet Protocol version 6, or IPv6. IPv6 uses much larger 128-bit addresses. This provides approximately 340 undecillion addresses.

TCP and IP protocols development timeline-en
TCP and IP protocols development timeline-en

Deployment of IPv6 has increased since around 2006. Currently, over 41% of Google's traffic is carried over IPv6 connections.

IP is described as a connectionless datagram service. This means it provides what is called "best-effort" delivery. The protocol is considered unreliable because it does not guarantee perfection. Various fault conditions can occur during transmission. These include data corruption, packet loss, or the duplication of packets. Because routing is dynamic, packets may take different paths to the same destination. This can result in packets arriving out of order. The design follows the end-to-end principle. This principle places the intelligence in the end nodes rather than the network itself.

UDP encapsulation
UDP encapsulation

Technical constraints like the Maximum Transmission Unit, or MTU, also affect how IP works. The MTU is the maximum size of a data packet allowed on a specific link. In IPv4, the protocol can automatically perform fragmentation. This means it breaks a large datagram into smaller units if the link MTU is exceeded. IPv4 also provides a way to re-order these fragments. In contrast, IPv6 does not perform fragmentation within network elements. Instead, it requires end hosts to avoid exceeding the path MTU. This difference reflects how the two versions manage network resources and complexity.

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File:UDP encapsulation.svg
UDP encapsulation.svg
File:TCP and IP protocols development timeline-en.svg
TCP and IP protocols development timeline-en.svg
File:First Internet Demonstration, 1977.jpg
First Internet Demonstration, 1977.jpg
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