====== Connectionless Communication Service ======

A //connectionless communication service// is a [[communication service model]] in which data packets are simply transmitted from [[end-system]] to [[end-system]] without any form of [[error detection]] (except perhaps for simple [[checksum|checksumming]]). In the [[Internet]], a //connectionless service// will rely on the "best-effort" [[datagram]] delivery service provided by the [[ip|Internet Protocol]] (IP) itself. There is no [[connection set-up]] or [[connection_tear-down|tear-down]] overhead, which means that //connectionless service// is likely to be somewhat more efficient than a [[connection-oriented|connection-oriented service]]. Also, as there is no [[error detection]] or [[flow control]], the data can probably be sent quickly which may be important for some time-critical applications such as [[streaming multimedia]] or [[voip|voice-over-IP]]. Conversely, as there is no [[flow control]] data may be transmitted more quickly than the network can deliver it, or the receiving [[application]] can process it; and without [[congestion control]] datagrams can be lost and the sender will not be asked to resend them. Thus it is important that a //connectionless service// is only used when some data loss can be tolerated.

The [[udp|User Datagram Protocol]] (UDP) is the //connectionless communication service// that is used on the [[Internet]]. UDP can be used to implement a [[connection-oriented|connection-oriented service]], but it will require the [[error-correction]] protocols to be built into the [[application layer]].


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