Connectionless communication

Connectionless communication, often referred to as CL-mode communication, is a data transmission method used in packet switching networks in which each data unit is individually addressed and routed based on information carried in each unit, rather than in the setup information of a prearranged, fixed data channel as in connection-oriented communication. Under connectionless communication between two network end points, 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 recipient is available and ready to receive the data. Some protocols allow for error correction by requesting retransmission. Internet Protocol (IP) and User Datagram Protocol (UDP) are connectionless protocols. A packet transmitted in a connectionless mode is frequently called a datagram. Connectionless protocols are usually described as stateless protocols because the end points have no protocol-defined way to remember where they are in a "conversation" of message exchanges. Connectionless communication has lower overhead than connection-oriented communication because in connection-oriented communication the communicating peers must first establish a logical or physical data channel or connection in a dialog preceding the exchange of user data. Connectionless communication allows for multicast and broadcast operations in which the same data are transmitted to several recipients in a single transmission. In connectionless transmissions the service provider usually cannot guarantee that there will be no loss, error insertion, misdelivery, duplication, or out-of-sequence delivery of the packet. However, the effect of errors may be reduced by implementing error correction within an application protocol. In connectionless mode there is less opportunity for optimization possible when sending several data units between the same two peers.