Connectionless(CL) refers to data exchange between computers in which no connection is switched between the respective participants and no acknowledgement of receipt is made by the destination station.
In connectionless technology, all transmission requests are organized in data packets and transmitted using data packet switching. The individual data packets contain the complete destination address and independently search for their way through the network to the receiver. There is no acknowledgement of the data packets. The sending station has no information about whether the data packets have reached the destination station.
The datagram service is a typical connectionless service. When datagrams are transmitted, it happens that they reach the destination system in different order. Due to the low administrative overhead compared to connection-oriented services, connectionless transmission achieves a higher data throughput.