Internet Protocol

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The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.

IP has the task of delivering packets from the source host to the destination host solely based on the IP addresses in the packet headers. For this purpose, IP defines packet structures that encapsulate the data to be delivered. It also defines addressing methods that are used to label the datagram with source and destination information. IP was the connectionless datagram service in the original Transmission Control Program introduced by Vint Cerf and Bob Kahn in 1974, which was complemented by a connection-oriented service that became the basis for the Transmission Control Protocol (TCP). The Internet protocol suite is therefore often referred to as TCP/IP.

The first major version of IP, Internet Protocol version 4 (IPv4), is the dominant protocol of the Internet. Its successor is Internet Protocol version 6 (IPv6), which has been in increasing deployment on the public Internet since around 2006. [1]

Function

Encapsulation of application data carried by UDP to a link protocol frame UDP encapsulation.svg
Encapsulation of application data carried by UDP to a link protocol frame

The Internet Protocol is responsible for addressing host interfaces, encapsulating data into datagrams (including fragmentation and reassembly) and routing datagrams from a source host interface to a destination host interface across one or more IP networks. [2] For these purposes, the Internet Protocol defines the format of packets and provides an addressing system.

Each datagram has two components: a header and a payload. The IP header includes a source IP address, a destination IP address, and other metadata needed to route and deliver the datagram. The payload is the data that is transported. This method of nesting the data payload in a packet with a header is called encapsulation.

IP addressing entails the assignment of IP addresses and associated parameters to host interfaces. The address space is divided into subnets, involving the designation of network prefixes. IP routing is performed by all hosts, as well as routers, whose main function is to transport packets across network boundaries. Routers communicate with one another via specially designed routing protocols, either interior gateway protocols or exterior gateway protocols, as needed for the topology of the network. [3]

Addressing methods

Routing schemes
Unicast

Unicast.svg

Broadcast

Broadcast.svg

Multicast

Multicast.svg

Anycast

Anycast-BM.svg

There are four principal addressing methods in the Internet Protocol:

Version history

A timeline for the development of the transmission control Protocol TCP and Internet Protocol IP TCP and IP protocols development timeline-en.svg
A timeline for the development of the transmission control Protocol TCP and Internet Protocol IP
First Internet demonstration, linking the ARPANET, PRNET, and SATNET on November 22, 1977 First Internet Demonstration, 1977.jpg
First Internet demonstration, linking the ARPANET, PRNET, and SATNET on November 22, 1977

In May 1974, the Institute of Electrical and Electronics Engineers (IEEE) published a paper entitled "A Protocol for Packet Network Intercommunication". [5] The paper's authors, Vint Cerf and Bob Kahn, described an internetworking protocol for sharing resources using packet switching among network nodes. A central control component of this model was the Transmission Control Program that incorporated both connection-oriented links and datagram services between hosts. The monolithic Transmission Control Program was later divided into a modular architecture consisting of the Transmission Control Protocol and User Datagram Protocol at the transport layer and the Internet Protocol at the internet layer. The model became known as the Department of Defense (DoD) Internet Model and Internet protocol suite , and informally as TCP/IP.

The following Internet Experiment Note (IEN) documents describe the evolution of the Internet Protocol into the modern version of IPv4: [6]

IP versions 1 to 3 were experimental versions, designed between 1973 and 1978. [7] Versions 2 and 3 supported variable-length addresses ranging between 1 and 16 octets (between 8 and 128 bits). [8] An early draft of version 4 supported variable-length addresses of up to 256 octets (up to 2048 bits) [9] but this was later abandoned in favor of a fixed-size 32-bit address in the final version of IPv4. This remains the dominant internetworking protocol in use in the Internet Layer; the number 4 identifies the protocol version, carried in every IP datagram. IPv4 is defined in RFC   791 (1981).

Version number 5 was used by the Internet Stream Protocol, an experimental streaming protocol that was not adopted. [7]

The successor to IPv4 is IPv6. IPv6 was a result of several years of experimentation and dialog during which various protocol models were proposed, such as TP/IX ( RFC   1475), PIP ( RFC   1621) and TUBA (TCP and UDP with Bigger Addresses, RFC   1347). Its most prominent difference from version 4 is the size of the addresses. While IPv4 uses 32 bits for addressing, yielding c. 4.3 billion (4.3×109) addresses, IPv6 uses 128-bit addresses providing c. 3.4×1038 addresses. Although adoption of IPv6 has been slow, as of January 2023, most countries in the world show significant adoption of IPv6, [10] with over 41% of Google's traffic being carried over IPv6 connections. [11]

The assignment of the new protocol as IPv6 was uncertain until due diligence assured that IPv6 had not been used previously. [12] Other Internet Layer protocols have been assigned version numbers, [13] such as 7 (IP/TX), 8 and 9 (historic). Notably, on April 1, 1994, the IETF published an April Fools' Day RfC about IPv9. [14] IPv9 was also used in an alternate proposed address space expansion called TUBA. [15] A 2004 Chinese proposal for an IPv9 protocol appears to be unrelated to all of these, and is not endorsed by the IETF.

Reliability

The design of the Internet protocol suite adheres to the end-to-end principle, a concept adapted from the CYCLADES project. Under the end-to-end principle, the network infrastructure is considered inherently unreliable at any single network element or transmission medium and is dynamic in terms of the 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 located in the end nodes.

As a consequence of this design, the Internet Protocol only provides best-effort delivery and its service is characterized as unreliable. In network architectural parlance, it is a connectionless protocol, in contrast to connection-oriented communication. Various fault conditions may occur, such as data corruption, packet loss and duplication. Because routing is dynamic, meaning every packet is treated independently, and because the network maintains no state based on the path of prior packets, different packets may be routed to the same destination via different paths, resulting in out-of-order delivery to the receiver.

All fault conditions in the network must be detected and compensated by the participating end nodes. The upper layer protocols of the Internet protocol suite are responsible for resolving reliability issues. For example, a host may buffer network data to ensure correct ordering before the data is delivered to an application.

IPv4 provides safeguards to ensure that the header of an IP packet is error-free. A routing node discards packets that fail a header checksum test. Although the Internet Control Message Protocol (ICMP) provides notification of errors, a routing node is not required to notify either end node of errors. IPv6, by contrast, operates without header checksums, since current link layer technology is assumed to provide sufficient error detection. [16] [17]

The dynamic nature of the Internet and the diversity of its components provide no guarantee that any particular path is actually capable of, or suitable for, performing the data transmission requested. One of the technical constraints is the size of data packets possible on a given link. Facilities exist to examine the maximum transmission unit (MTU) size of the local link and Path MTU Discovery can be used for the entire intended path to the destination. [18]

The IPv4 internetworking layer automatically fragments a datagram into smaller units for transmission when the link MTU is exceeded. IP provides re-ordering of fragments received out of order. [19] An IPv6 network does not perform fragmentation in network elements, but requires end hosts and higher-layer protocols to avoid exceeding the path MTU. [20]

The Transmission Control Protocol (TCP) is an example of a protocol that adjusts its segment size to be smaller than the MTU. The User Datagram Protocol (UDP) and ICMP disregard MTU size, thereby forcing IP to fragment oversized datagrams. [21]

Security

During the design phase of the ARPANET and the early Internet, the security aspects and needs of a public, international network could not be adequately anticipated. Consequently, many Internet protocols exhibited vulnerabilities highlighted by network attacks and later security assessments. In 2008, a thorough security assessment and proposed mitigation of problems was published. [22] The IETF has been pursuing further studies. [23]

See also

Related Research Articles

An Internet Protocol address is a numerical label such as 192.0.2.1 that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface identification, and location addressing.

The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information indicating success or failure when communicating with another IP address. For example, an error is indicated when a requested service is not available or that a host or router could not be reached. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications.

<span class="mw-page-title-main">IPv4</span> Fourth version of the Internet Protocol

Internet Protocol version 4 (IPv4) is the first version of the Internet Protocol (IP) as a standalone specification. It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv4 was the first version deployed for production on SATNET in 1982 and on the ARPANET in January 1983. It is still used to route most Internet traffic today, even with the ongoing deployment of Internet Protocol version 6 (IPv6), its successor.

<span class="mw-page-title-main">IPv6</span> Version 6 of the Internet Protocol

Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion, and was intended to replace IPv4. In December 1998, IPv6 became a Draft Standard for the IETF, which subsequently ratified it as an Internet Standard on 14 July 2017.

The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and the Internet Protocol (IP). Early versions of this networking model were known as the Department of Defense (DoD) model because the research and development were funded by the United States Department of Defense through DARPA.

In computer networking, the maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction. The MTU relates to, but is not identical to the maximum frame size that can be transported on the data link layer, e.g., Ethernet frame.

The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered, and error-checked delivery of a stream of octets (bytes) between applications running on hosts communicating via an IP network. Major internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP, which is part of the transport layer of the TCP/IP suite. SSL/TLS often runs on top of TCP.

In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages to other hosts on an Internet Protocol (IP) network. Within an IP network, UDP does not require prior communication to set up communication channels or data paths.

The Address Resolution Protocol (ARP) is a communication protocol used for discovering the link layer address, such as a MAC address, associated with a given internet layer address, typically an IPv4 address. This mapping is a critical function in the Internet protocol suite. ARP was defined in 1982 by RFC 826, which is Internet Standard STD 37.

In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers.

<span class="mw-page-title-main">IP fragmentation</span> Process that breaks IP packets into smaller pieces

IP fragmentation is an Internet Protocol (IP) process that breaks packets into smaller pieces (fragments), so that the resulting pieces can pass through a link with a smaller maximum transmission unit (MTU) than the original packet size. The fragments are reassembled by the receiving host.

A broadcast address is a network address used to transmit to all devices connected to a multiple-access communications network. A message sent to a broadcast address may be received by all network-attached hosts.

The maximum segment size (MSS) is a parameter of the Options field of the TCP header that specifies the largest amount of data, specified in bytes, that a computer or communications device can receive in a single TCP segment. It does not count the TCP header or the IP header. The IP datagram containing a TCP segment may be self-contained within a single packet, or it may be reconstructed from several fragmented pieces; either way, the MSS limit applies to the total amount of data contained in the final, reconstructed TCP segment.

Mobile IP is an Internet Engineering Task Force (IETF) standard communications protocol that is designed to allow mobile device users to move from one network to another while maintaining a permanent IP address. Mobile IP for IPv4 is described in IETF RFC 5944, and extensions are defined in IETF RFC 4721. Mobile IPv6, the IP mobility implementation for the next generation of the Internet Protocol, IPv6, is described in RFC 6275.

A network socket is a software structure within a network node of a computer network that serves as an endpoint for sending and receiving data across the network. The structure and properties of a socket are defined by an application programming interface (API) for the networking architecture. Sockets are created only during the lifetime of a process of an application running in the node.

Path MTU Discovery (PMTUD) is a standardized technique in computer networking for determining the maximum transmission unit (MTU) size on the network path between two Internet Protocol (IP) hosts, usually with the goal of avoiding IP fragmentation. PMTUD was originally intended for routers in Internet Protocol Version 4 (IPv4). However, all modern operating systems use it on endpoints. In IPv6, this function has been explicitly delegated to the end points of a communications session. As an extension to the standard path MTU discovery, a technique called Packetization Layer Path MTU Discovery works without support from ICMP.

A routing protocol specifies how routers communicate with each other to distribute information that enables them to select paths between nodes on a computer network. Routers perform the traffic directing functions on the Internet; data packets are forwarded through the networks of the internet from router to router until they reach their destination computer. Routing algorithms determine the specific choice of route. Each router has a prior knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbors, and then throughout the network. This way, routers gain knowledge of the topology of the network. The ability of routing protocols to dynamically adjust to changing conditions such as disabled connections and components and route data around obstructions is what gives the Internet its fault tolerance and high availability.

The internet layer is a group of internetworking methods, protocols, and specifications in the Internet protocol suite that are used to transport network packets from the originating host across network boundaries; if necessary, to the destination host specified by an IP address. The internet layer derives its name from its function facilitating internetworking, which is the concept of connecting multiple networks with each other through gateways.

In wired computer networking a hop occurs when a packet is passed from one network segment to the next. Data packets pass through routers as they travel between source and destination. The hop count refers to the number of network devices through which data passes from source to destination.

An IPv6 packet is the smallest message entity exchanged using Internet Protocol version 6 (IPv6). Packets consist of control information for addressing and routing and a payload of user data. The control information in IPv6 packets is subdivided into a mandatory fixed header and optional extension headers. The payload of an IPv6 packet is typically a datagram or segment of the higher-level transport layer protocol, but may be data for an internet layer or link layer instead.

References

  1. ↑ The Economics of Transition to Internet Protocol version 6 (IPv6) (Report). OECD Digital Economy Papers. OECD. 2014-11-06. doi: 10.1787/5jxt46d07bhc-en . Archived from the original on 2021-03-07. Retrieved 2020-12-04.
  2. ↑ Charles M. Kozierok, The TCP/IP Guide, archived from the original on 2019-06-20, retrieved 2017-07-22
  3. ↑ "IP Technologies and Migration — EITC". www.eitc.org. Archived from the original on 2021-01-05. Retrieved 2020-12-04.
  4. ↑ Goścień, Róża; Walkowiak, Krzysztof; Klinkowski, Mirosław (2015-03-14). "Tabu search algorithm for routing, modulation and spectrum allocation in elastic optical network with anycast and unicast traffic". Computer Networks. 79: 148–165. doi:10.1016/j.comnet.2014.12.004. ISSN   1389-1286.
  5. ↑ Cerf, V.; Kahn, R. (1974). "A Protocol for Packet Network Intercommunication" (PDF). IEEE Transactions on Communications. 22 (5): 637–648. doi:10.1109/TCOM.1974.1092259. ISSN   1558-0857. Archived (PDF) from the original on 2017-01-06. Retrieved 2020-04-06. The authors wish to thank a number of colleagues for helpful comments during early discussions of international network protocols, especially R. Metcalfe, R. Scantlebury, D. Walden, and H. Zimmerman; D. Davies and L. Pouzin who constructively commented on the fragmentation and accounting issues; and S. Crocker who commented on the creation and destruction of associations.
  6. ↑ "Internet Experiment Note Index". www.rfc-editor.org. Retrieved 2024-01-21.
  7. 1 2 Stephen Coty (2011-02-11). "Where is IPv1, 2, 3, and 5?". Archived from the original on 2020-08-02. Retrieved 2020-03-25.
  8. ↑ Postel, Jonathan B. (February 1978). "Draft Internetwork Protocol Specification Version 2" (PDF). RFC Editor. IEN 28. Retrieved 6 October 2022. Archived 16 May 2019 at the Wayback Machine
  9. ↑ Postel, Jonathan B. (June 1978). "Internetwork Protocol Specification Version 4" (PDF). RFC Editor. IEN 41. Retrieved 11 February 2024. Archived 16 May 2019 at the Wayback Machine
  10. ↑ Strowes, Stephen (4 Jun 2021). "IPv6 Adoption in 2021". RIPE Labs. Archived from the original on 2021-09-20. Retrieved 2021-09-20.
  11. ↑ "IPv6". Google. Archived from the original on 2020-07-14. Retrieved 2023-05-19.
  12. ↑ Mulligan, Geoff. "It was almost IPv7". O'Reilly. Archived from the original on 5 July 2015. Retrieved 4 July 2015.
  13. ↑ "IP Version Numbers". Internet Assigned Numbers Authority. Archived from the original on 2019-01-18. Retrieved 2019-07-25.
  14. ↑ RFC   1606: A Historical Perspective On The Usage Of IP Version 9. April 1, 1994.
  15. ↑ Ross Callon (June 1992). TCP and UDP with Bigger Addresses (TUBA), A Simple Proposal for Internet Addressing and Routing. doi: 10.17487/RFC1347 . RFC 1347.
  16. ↑ RFC   1726 section 6.2
  17. ↑ RFC   2460
  18. ↑ Rishabh, Anand (2012). Wireless Communication. S. Chand Publishing. ISBN   978-81-219-4055-9. Archived from the original on 2024-06-12. Retrieved 2020-12-11.
  19. ↑ Siyan, Karanjit. Inside TCP/IP, New Riders Publishing, 1997. ISBN   1-56205-714-6
  20. ↑ Bill Cerveny (2011-07-25). "IPv6 Fragmentation". Arbor Networks. Archived from the original on 2016-09-16. Retrieved 2016-09-10.
  21. ↑ Parker, Don (2 November 2010). "Basic Journey of a Packet". Symantec . Symantec. Archived from the original on 20 January 2022. Retrieved 4 May 2014.
  22. ↑ Fernando Gont (July 2008), Security Assessment of the Internet Protocol (PDF), CPNI, archived from the original (PDF) on 2010-02-11
  23. ↑ F. Gont (July 2011). Security Assessment of the Internet Protocol version 4. doi: 10.17487/RFC6274 . RFC 6274.
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