ConnectionOriented

Connection-oriented refers to a communication service in which a network connection is established between two endpoints before data transfer and is maintained for the duration of the session. This approach creates a stateful channel that supports reliable data transfer, sequencing, and flow control.

Key characteristics include the establishment of a session through a handshake, per-connection state maintained by the endpoints or network elements, and guarantees such as ordered delivery and, in many cases, reliability through retransmission of lost data. Sequencing ensures that data arrives in the correct order, while flow control and congestion control regulate the rate of transmission to prevent overwhelming the receiver or the network.

In practice, connection-oriented protocols often implement a handshake to initiate the session, followed by data transfer with acknowledgments and possible retransmissions. A well-known example is the Transmission Control Protocol (TCP) in the Internet protocol suite, which uses a three-way handshake to establish connections and provides a reliable, byte-stream service. Other examples include SCTP and network-layer virtual circuit protocols such as those used in ATM or X.25 networks.

By contrast, connectionless communication sends data without a prior setup or maintained state, delivering datagrams that may arrive out of order or be dropped, with no inherent guarantees. Connection-oriented services incur more overhead and latency due to setup and state maintenance but are preferred when reliability and ordered delivery are important, such as file transfers, web traffic, and email. They may be less suitable for low-latency or multicast scenarios where simplicity and speed are prioritized.