What is connectionless service?
A connectionless service is a concept in data communication that is used to transfer data on the transport layer (layer 4) of the OSI model. It describes the communication between two nodes or terminals in which data is sent from one node to another without first ensuring that the destination is available and ready to receive the data. A session connection between the sender and the receiver is not required, the sender is just beginning to send the data. The message or datagram is sent without prior agreement, which is a less reliable but faster transaction than a connection-oriented service.
User Datagram Protocol (UDP) is a connectionless protocol, while Transmission Control Protocol (TCP) is a connection-oriented network protocol.
Connectionless service means that a terminal or node can send data packets to its destination without establishing a connection to the destination. This works because of error handling protocols that allow for error correction such as requesting a retransmission. LANs are actually connectionless systems, whereby any computer can transmit data packets as soon as it can access the network.
The Internet is a large, connectionless parcel network in which all parcel deliveries are handled by Internet providers. If necessary, TCP also adds connection-oriented services in addition to IP. TCP can provide all of the top-level connection services required for proper data delivery.