Connection-oriented
Encyclopedia
Connection-oriented communication is a data communication mode in telecommunication
s whereby the devices at the end points use a protocol to establish an end-to-end
logical or physical connection before any data may be sent. In case of digital transmission, in-order delivery of a bit stream or byte stream
is provided. Connection-oriented protocol
services are often but not always reliable
network services, that provide acknowledgment after successful delivery, and automatic repeat request functions in case of missing data or detected bit-errors.
Circuit mode communication, for example the public switched telephone network
, ISDN, SONET/SDH and optical mesh networks, are examples of connection-oriented communication. Circuit mode communication provides guarantees that data will arrive with constant bandwidth and at constant delay.
Packet mode communication may also be connection-oriented, which is called virtual circuit
mode communication. Due to the packet switching, the communication may suffer from variable bit rate and delay, due to varying traffic load and packet queue lengths.
A connection-oriented transport layer
protocol, such as TCP
, may be based on a connectionless network layer protocol (such as IP
), but still achieve in-order delivery of a byte-stream, by means of segment numbering on the sender side and data packet reordering on the receiver side.
In a connection-oriented packet switched data link layer
or network layer
protocol, all data is sent over the same path during a communication session. The protocol does not have to provide each packet with routing information (complete source and destination address), but only with a channel/data stream number, often denoted virtual circuit identifier
(VCI). Routing information may be provided to the network nodes during the connection establishment phase, where the VCI is defined in tables in each node. Thus, the actual packet switching and data transfer can be taken care of by fast hardware, as opposed to slow software based routing.
The alternative to connection-oriented transmission is connectionless communication, also known as datagram
communication, in which data is sent in form of packets from one end point to another without prior arrangement or signaling. This mode operates without guarantees of delivery according to a best-effort policy. Each data packet must contain complete address information, since packets are routed individually and independently of each other, possibly transmitted along different network paths.
Connectionless protocol
s are usually described as stateless because the end points have no protocol-defined way to remember where they are in a "conversation" of message exchanges. Because they can keep track of a conversation, connection-oriented protocols are sometimes described as stateful.
Examples of connection-oriented packet mode communication, i.e. virtual circuit mode communication:
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
s whereby the devices at the end points use a protocol to establish an end-to-end
End-to-end
End-to-end or End to End may refer to:*Land's End to John o'Groats, the journey from "End to End" across Great Britain*End-to-end auditable voting systems, a voting system*End-to-end principle, a principal design element of the Internet...
logical or physical connection before any data may be sent. In case of digital transmission, in-order delivery of a bit stream or byte stream
Byte stream
In computer science, a byte stream is a bit stream, in which data bits are grouped into units, called bytes.In computer networking the term octet stream is sometimes used to refer to the same thing; it emphasizes the use of bytes having the length of 8 bits, known as octets.Formally, a byte stream...
is provided. Connection-oriented protocol
Connection-oriented protocol
A connection-oriented networking protocol is one that establishes a communication session, then delivers a stream of data in the same order as it was sent. It may be a circuit switched connection, or a virtual circuit connection in a packet switched network...
services are often but not always reliable
Reliability (computer networking)
In computer networking, a reliable protocol is one that provides reliability properties with respect to the delivery of data to the intended recipient, as opposed to an unreliable protocol, which does not provide notifications to the sender as to the delivery of transmitted data.A reliable...
network services, that provide acknowledgment after successful delivery, and automatic repeat request functions in case of missing data or detected bit-errors.
Circuit mode communication, for example the public switched telephone network
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
, ISDN, SONET/SDH and optical mesh networks, are examples of connection-oriented communication. Circuit mode communication provides guarantees that data will arrive with constant bandwidth and at constant delay.
Packet mode communication may also be connection-oriented, which is called virtual circuit
Virtual circuit
In telecommunications and computer networks, a virtual circuit , synonymous with virtual connection and virtual channel, is a connection oriented communication service that is delivered by means of packet mode communication...
mode communication. Due to the packet switching, the communication may suffer from variable bit rate and delay, due to varying traffic load and packet queue lengths.
A connection-oriented transport layer
Transport layer
In computer networking, the transport layer or layer 4 provides end-to-end communication services for applications within a layered architecture of network components and protocols...
protocol, such as TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
, may be based on a connectionless network layer protocol (such as IP
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
), but still achieve in-order delivery of a byte-stream, by means of segment numbering on the sender side and data packet reordering on the receiver side.
In a connection-oriented packet switched data link layer
Data link layer
The data link layer is layer 2 of the seven-layer OSI model of computer networking. It corresponds to, or is part of the link layer of the TCP/IP reference model....
or network layer
Network layer
The network layer is layer 3 of the seven-layer OSI model of computer networking.The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking.The network...
protocol, all data is sent over the same path during a communication session. The protocol does not have to provide each packet with routing information (complete source and destination address), but only with a channel/data stream number, often denoted virtual circuit identifier
Virtual Circuit Identifier
A Virtual Channel Identifier is a unique identifier which indicates a particular virtual circuit on a network. It is a 16-bit field in the header of an ATM cell...
(VCI). Routing information may be provided to the network nodes during the connection establishment phase, where the VCI is defined in tables in each node. Thus, the actual packet switching and data transfer can be taken care of by fast hardware, as opposed to slow software based routing.
The alternative to connection-oriented transmission is connectionless communication, also known as datagram
Datagram
A datagram is a basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order are not guaranteed....
communication, in which data is sent in form of packets from one end point to another without prior arrangement or signaling. This mode operates without guarantees of delivery according to a best-effort policy. Each data packet must contain complete address information, since packets are routed individually and independently of each other, possibly transmitted along different network paths.
Connectionless protocol
Connectionless protocol
In telecommunications, connectionless describes communication between two network end points in which a message can be sent from one end point to another without prior arrangement. The device at one end of the communication transmits data addressed to the other, without first ensuring that the...
s are usually described as stateless because the end points have no protocol-defined way to remember where they are in a "conversation" of message exchanges. Because they can keep track of a conversation, connection-oriented protocols are sometimes described as stateful.
Examples of connection-oriented packet mode communication, i.e. virtual circuit mode communication:
- The Transmission Control ProtocolTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
(TCP) is a connection-oriented reliable protocol that is based on a datagramDatagramA datagram is a basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order are not guaranteed....
protocol (the IP protocol). - X.25X.25X.25 is an ITU-T standard protocol suite for packet switched wide area network communication. An X.25 WAN consists of packet-switching exchange nodes as the networking hardware, and leased lines, Plain old telephone service connections or ISDN connections as physical links...
is a connection-oriented reliable network protocol. - Frame relayFrame relayFrame Relay is a standardized wide area network technology that specifies the physical and logical link layers of digital telecommunications channels using a packet switching methodology...
is a connection-oriented unreliable data link layer protocol. - GPRS
- Asynchronous Transfer ModeAsynchronous Transfer ModeAsynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
- Multiprotocol Label SwitchingMultiprotocol Label SwitchingMultiprotocol Label Switching is a mechanism in high-performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table. The labels identify virtual links between...
See also
- Connectionless communication
- Packet switchingPacket switchingPacket switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...
- Statistical multiplexingStatistical multiplexingStatistical multiplexing is a type of communication link sharing, very similar to dynamic bandwidth allocation . In statistical multiplexing, a communication channel is divided into an arbitrary number of variable bit-rate digital channels or data streams. The link sharing is adapted to the...
- Packet
- Virtual circuitVirtual circuitIn telecommunications and computer networks, a virtual circuit , synonymous with virtual connection and virtual channel, is a connection oriented communication service that is delivered by means of packet mode communication...