telecommunication Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

s and

computer networking A computer network is a collection of communicating computers and other devices, such as printers and smart phones. In order to communicate, the computers and devices must be connected by wired media like copper cables, optical fibers, or b ...

, connection-oriented communication is a

communication protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer science), sem ...

where a communication session or a semi-permanent connection is established before any useful data can be transferred. The established connection ensures that data is delivered in the correct order to the upper communication layer. The alternative is called ''

connectionless communication Connectionless communication, often referred to as CL-mode communication,Information Processing Systems - Open Systems Interconnection, "Transport Service Definition - Addendum 1: Connectionless-mode Transmission", International Organization for ...

'', such as the

datagram A datagram is a basic transfer unit associated with a packet-switched network. Datagrams are typically structured in header and payload sections. Datagrams provide a connectionless communication service across a packet-switched network. The de ...

mode communication used by

Internet Protocol 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 ...

(IP) and

User Datagram Protocol In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in Network packet, packets) to other hosts on an Internet Protoco ...

(UDP), where data may be delivered out of order, since different

network packet In telecommunications and computer networking, a network packet is a formatted unit of Data (computing), data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the ''Payload ...

s are routed independently and may be delivered over different paths. Connection-oriented communication may be implemented with a circuit switched connection, or a packet-mode

virtual circuit A virtual circuit (VC) is a means of transporting data over a data network, based on packet switching and in which a connection is first established across the network between two endpoints. The network, rather than having a fixed data rate reser ...

connection. In the latter case, it may use either a transport layer virtual circuit protocol such as the

Transmission Control Protocol The Transmission Control Protocol (TCP) is one of the main communications protocol, protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, th ...

(TCP) protocol, allowing data to be delivered in order. Although the lower-layer switching is connectionless, or it may be a

data link layer The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer p ...

network layer 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 Router (computing), routers. Functions The network layer provides t ...

switching mode, where all data packets belonging to the same traffic stream are delivered over the same path, and traffic flows are identified by some ''connection identifier'' reducing the overhead of routing decisions on a packet-by-packet basis for the network. Connection-oriented protocol services are often, but not always, '' reliable'' network services that provide acknowledgment after successful delivery and

automatic repeat request Automatic repeat request (ARQ), also known as automatic repeat query, is an error-control method for data transmission that uses acknowledgements (messages sent by the receiver indicating that it has correctly received a message) and timeout ...

functions in case of missing or corrupted data.

Asynchronous Transfer Mode Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by the American National Standards Institute and International Telecommunication Union Telecommunication Standardization Sector (ITU-T, formerly CCITT) for digital trans ...

(ATM),

Frame Relay Frame Relay (FR) is a standardized wide area network (WAN) technology that specifies the Physical layer, physical and data link layers of digital telecommunications channels using a packet switching methodology. Frame Relay was originally devel ...

and

Multiprotocol Label Switching Multiprotocol Label Switching (MPLS) is a routing technique in telecommunications networks that directs data from one node to the next based on labels rather than network addresses. Whereas network addresses identify endpoints, the labels iden ...

(MPLS) are examples of connection-oriented unreliable protocols.

Simple Mail Transfer Protocol The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typ ...

(SMTP) is an example of a connection-oriented protocol in which, if a message is not delivered, an error report is sent to the sender, making it a reliable protocol. Because they can keep track of a conversation, connection-oriented protocols are sometimes described as stateful.

Circuit switching

Circuit switched communication, for example the

public switched telephone network The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony. The PSTN consists o ...

ISDN Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. ...

SONET/SDH Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diod ...

and

optical mesh network An optical mesh network is a type of Optical networking, optical telecommunications network employing wired fiber-optic communication or wireless free-space optical communication in a Mesh networking, mesh network architecture. Most optical mesh ...

s, are intrinsically connection-oriented communication systems. Circuit-mode communication provides guarantees that constant bandwidth will be available, and

bit stream A bitstream (or bit stream), also known as binary sequence, is a sequence of bits. A bytestream is a sequence of bytes. Typically, each byte is an 8-bit quantity, and so the term octet stream is sometimes used interchangeably. An octet may ...

byte stream A bitstream (or bit stream), also known as binary sequence, is a sequence of bits. A bytestream is a sequence of bytes. Typically, each byte is an Octet (computing), 8-bit quantity, and so the term octet stream is sometimes used interchangeab ...

data will arrive in order with constant delay. The switches are reconfigured during a circuit establishment phase.

Virtual circuit switching

Packet switched In telecommunications, packet switching is a method of grouping data into short messages in fixed format, i.e. '' packets,'' that are transmitted over a digital network. Packets consist of a header and a payload. Data in the header is used b ...

communication may also be connection-oriented, which is called

mode communication. Due to packet switching, communication may suffer from variable bit rates and delays, due to varying traffic loads and packet queue lengths. Connection-oriented communication does not necessarily imply

reliability Reliability, reliable, or unreliable may refer to: Science, technology, and mathematics Computing * Data reliability (disambiguation), a property of some disk arrays in computer storage * Reliability (computer networking), a category used to des ...

Transport layer

Connection-oriented

transport-layer protocol In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end c ...

s provide connection-oriented communications over connectionless communication systems. A connection-oriented transport layer protocol, such as TCP, may be based on a connectionless

network-layer protocol 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. Functions The network layer provides the means of transf ...

such as IP, but still achieves in-order delivery of a byte-stream by means of segment sequence numbering on the sender side, packet buffering, and data packet reordering on the receiver side.

Datalink and network layer

In a connection-oriented packet-switched data-link or

, all data is sent over the same path during a communication session. Rather than using complete routing information for each packet (source and destination addresses) as in connectionless datagram switching such as conventional IP routers, a connection-oriented protocol identifies traffic flows only by a channel or data stream number, often denoted

virtual circuit identifier Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by the American National Standards Institute and International Telecommunication Union Telecommunication Standardization Sector (ITU-T, formerly CCITT) for digital tran ...

(VCI). Routing information may be provided to the network nodes during the connection establishment phase, where the VCI is defined in tables within each node. Thus, the actual packet switching and data transfer can be taken care of by fast hardware, as opposed to slower software-based routing. Typically, this connection identifier is a small integer (for example, 10 bits for Frame Relay and 24 bits for ATM). This makes network switches substantially faster. ATM and Frame Relay, for example, are both examples of connection-oriented, unreliable data link layer protocols. Reliable connectionless protocols exist as well, for example AX.25 network layer protocol when it passes data in I-frames, but this combination is rare, and reliable-connectionless is uncommon in modern networks. Some connection-oriented protocols have been designed or altered to accommodate both connection-oriented and connectionless data.

Examples

Examples of connection-oriented packet-mode communication, i.e. virtual circuit mode communication: *

* Connection-oriented Ethernet * Datagram Congestion Control Protocol *

General Packet Radio Service General Packet Radio Service (GPRS), also called 2.5G, is a mobile data standard on the 2G cellular communication network's global system for mobile communications (GSM). Networks and mobile devices with GPRS started to roll out around the ...

IPX/SPX IPX/SPX stands for Internetwork Packet Exchange/Sequenced Packet Exchange. IPX and SPX are networking protocols used initially on networks using the (since discontinued) Novell NetWare operating systems. They also became widely used on networks ...

Stream Control Transmission Protocol The Stream Control Transmission Protocol (SCTP) is a computer networking communications protocol in the transport layer of the Internet protocol suite. Originally intended for Signaling System 7 (SS7) message transport in telecommunication, the ...

Transparent Inter-process Communication Transparent Inter Process Communication (TIPC) is an inter-process communication (IPC) service in Linux designed for cluster-wide operation. It is sometimes presented as ''Cluster Domain Sockets'', in contrast to the well-known ''Unix Domain Socke ...

X.25 X.25 is an ITU-T standard protocol suite for Packet switched network, packet-switched data communication in wide area network, wide area networks (WAN). It was originally defined by the CCITT, International Telegraph and Telephone Consultative Co ...

References

{{DEFAULTSORT:Connection-oriented Computer networking Internet architecture Internet protocols Network protocols