Internet protocol suite. The Internet protocol suite is the computer networking model and set of communications protocols used on the Internet and similar computer networks. It is commonly known as TCP/IP, because its most important protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP), were the first networking protocols defined in this standard. Often also called the Internet model, it was originally also known as the DoD model, because the development of the networking model was funded by DARPA, an agency of the United States Department of Defense. TCP/IP provides end-to-end connectivity specifying how data should be packetized, addressed, transmitted, routed and received at the destination. The TCP/IP model and related protocol models are maintained by the Internet Engineering Task Force (IETF). History[edit] Early research[edit] Diagram of the first internetworked connection Specification[edit] Adoption[edit] Key architectural principles[edit] Abstraction layers[edit] Link layer[edit]
Link layer. Despite the different semantics of layering in TCP/IP and OSI, the link layer is sometimes described as a combination of the data link layer (layer 2) and the physical layer (layer 1) in the OSI model. However, the layers of TCP/IP are descriptions of operating scopes (application, host-to-host, network, link) and not detailed prescriptions of operating procedures, data semantics, or networking technologies. RFC 1122 exemplifies that local area network protocols such as Ethernet and IEEE 802, and framing protocols such as Point-to-Point Protocol (PPP) belong to the link layer.
Definition in standards and textbooks[edit] Local area networking standards such as Ethernet and IEEE 802 specifications use terminology from the seven-layer OSI model rather than the TCP/IP model. Link layer protocols[edit] The link layer in the TCP/IP model is a descriptive realm of networking protocols that operate only on the local network segment (link) that a host is connected to. Relation to OSI model[edit] Point-to-point protocol. PPP is used over many types of physical networks including serial cable, phone line, trunk line, cellular telephone, specialized radio links, and fiber optic links such as SONET.
PPP is also used over Internet access connections. Internet service providers (ISPs) have used PPP for customer dial-up access to the Internet, since IP packets cannot be transmitted over a modem line on their own, without some data link protocol. Two derivatives of PPP, Point-to-Point Protocol over Ethernet (PPPoE) and Point-to-Point Protocol over ATM (PPPoA), are used most commonly by Internet Service Providers (ISPs) to establish a Digital Subscriber Line (DSL) Internet service connection with customers. Description[edit] PPP was designed somewhat after the original HDLC specifications. RFC 2516 describes Point-to-Point Protocol over Ethernet (PPPoE) as a method for transmitting PPP over Ethernet that is sometimes used with DSL. PPP is a layered protocol that has three components: PPP is specified in RFC 1661.
Internet layer. Internet-layer protocols use IP-based packets. The internet layer does not include the protocols that define communication between local (on-link) network nodes which fulfill the purpose of maintaining link states between the local nodes, such as the local network topology, and that usually use protocols that are based on the framing of packets specific to the link types.
Such protocols belong to the link layer. A common design aspect in the internet layer is the robustness principle: "Be liberal in what you accept, and conservative in what you send"[1] as a misbehaving host can deny Internet service to many other users. Purpose[edit] The internet layer has three basic functions: In Version 4 of the Internet Protocol (IPv4), during both transmit and receive operations, IP is capable of automatic or intentional fragmentation or defragmentation of packets, based, for example, on the maximum transmission unit (MTU) of link elements.
Core protocols[edit] Security[edit] IETF standards[edit] Internet Protocol. This article is about the IP network protocol only. For Internet architecture or other protocols, see Internet protocol suite. The Internet Protocol (IP) is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. Historically, IP was the connectionless datagram service in the original Transmission Control Program introduced by Vint Cerf and Bob Kahn in 1974; the other being the connection-oriented 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. Function[edit] The Internet Protocol is responsible for addressing hosts and for routing datagrams (packets) from a source host to a destination host across one or more IP networks.
Datagram construction[edit] Reliability[edit] Transport layer. Transport layer implementations are contained in both the TCP/IP model (RFC 1122),[2] which is the foundation of the Internet, and the Open Systems Interconnection (OSI) model of general networking, however, the definitions of details of the transport layer are different in these models. In the Open Systems Interconnection model the transport layer is most often referred to as Layer 4. The best-known transport protocol is the Transmission Control Protocol (TCP).
It lent its name to the title of the entire Internet Protocol Suite, TCP/IP. It is used for connection-oriented transmissions, whereas the connectionless User Datagram Protocol (UDP) is used for simpler messaging transmissions. Services[edit] Transport layer services are conveyed to an application via a programming interface to the transport layer protocols. Analysis[edit] The transport layer is responsible for delivering data to the appropriate application process on the host computers. Protocols[edit] References[edit] Transmission Control Protocol. Web browsers use TCP when they connect to servers on the World Wide Web, and it is used to deliver email and transfer files from one location to another. HTTP, HTTPS, SMTP, POP3, IMAP, SSH, FTP, Telnet and a variety of other protocols are typically encapsulated in TCP.
Historical origin[edit] In May 1974 the Institute of Electrical and Electronic Engineers (IEEE) published a paper titled "A Protocol for Packet Network Intercommunication. "[1] The paper's authors, Vint Cerf and Bob Kahn, described an internetworking protocol for sharing resources using packet-switching among the 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 at the connection-oriented layer and the Internet Protocol at the internetworking (datagram) layer. Padding. Application layer. Although both models use the same term for their respective highest level layer, the detailed definitions and purposes are different. In the OSI model, the definition of the application layer is narrower in scope.
The OSI model defines the application layer as the user interface responsible for displaying received information to the user. In contrast, the Internet Protocol model does not concern itself with such detail. OSI also explicitly distinguishes additional functionality below the application layer, but above the transport layer at two additional levels; the session layer and the presentation layer.
TCP/IP protocols[edit] The IETF definition document for the application layer in the Internet Protocol Suite is RFC 1123. Other protocol examples[edit] References[edit] External links[edit] Hypertext Transfer Protocol. The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems.[1] HTTP is the foundation of data communication for the World Wide Web.
The standards development of HTTP was coordinated by the Internet Engineering Task Force (IETF) and the World Wide Web Consortium (W3C), culminating in the publication of a series of Requests for Comments (RFCs), most notably RFC 2616 (June 1999), which defined HTTP/1.1, the version of HTTP most commonly used today. In June 2014, RFC 2616 was retired and HTTP/1.1 was redefined by RFCs 7230, 7231, 7232, 7233, 7234, and 7235.[2] HTTP/2 is currently in draft form. Technical overview[edit] URL beginning with the HTTP scheme and the WWW domain name label. A web browser is an example of a user agent (UA).
HTTP is designed to permit intermediate network elements to improve or enable communications between clients and servers. History[edit] The first documented version of HTTP was HTTP V0.9 (1991). Stateless protocol. Examples of stateless protocols include the Internet Protocol (IP) which is the foundation for the Internet, and the Hypertext Transfer Protocol (HTTP) which is the foundation of data communication for the World Wide Web. Advantages and disadvantages[edit] The stateless design simplifies the server design because there is no need to dynamically allocate storage to deal with conversations in progress. If a client dies in mid-transaction, no part of the system needs to be responsible for cleaning up the present state of the server.
A disadvantage of statelessness is that it may be necessary to include additional information in every request, and this extra information will need to be interpreted by the server. Examples[edit] An example of a stateless protocol is HTTP.[1] The protocol provides no means of storing a user's data between requests. Contrast this with a traditional FTP server that conducts an interactive session with the user.
Stacking of stateless and stateful protocol layers[edit] POST.