Connection-Oriented Service and Protocols

Connection-oriented service provides reliable data delivery by establishing a virtual circuit between the sending host and the receiving host. Some characteristics of connection-oriented service are the following:

• The initial request for a session involves some setup time between the hosts .

• The server considers the connection as a virtual circuit.

• The server uses acknowledgments of data receipt to guarantee data delivery.

• Long transmissions are common.

Both TCP and SPX are connection-oriented protocols. SPX is the NetWare protocol for providing connection-oriented service. TCP uses ports between hosts to create a virtual circuit between two host computers on an IP network. TCP is not concerned with the process of routing through the network but is concerned with the data delivery in the datagram.

For example, if two host computers want to transfer Simple Mail Transfer Protocol (SMTP) traffic between them, the sending host requests a session with the receiving host on TCP port 25. After the initial protocol negotiation is complete, the virtual circuit is established, and the two hosts can guarantee data delivery. TCP and SPX are connection-oriented protocols, which are similar to a certified letter because the sender ensures that the recipient received the packet.