Connection-Oriented Protocol
NAS Recovery - Connection-Oriented Protocol
A connection-oriented protocol is a type of networking protocol which requires that a logical connection be established between the sender and the recipient before transferring data. In a typical connection-oriented protocol, one device sends request to open a connection, and the other responds. They pass control information to decide whether the connection should be set up. If the communication is successful, data is sent.
There may be two ways of communications: a circuit switched connection or a virtual circuit connection in a packed switched network. In virtual circuit connection, the protocol uses a connection identifier to identify traffic flows. A connection identifier is a small integer, typically 10 bits for Frame Relay and 24 for ATM. As a result, the network switches respond substantially faster, making even the connectionless protocols such as IP traffic being tagged with connection-oriented prefixes.
A popular connection-oriented protocol at the transport layer is Transmission Control Protocol or TCP. A phone call in which a user must dial the telephone, get an answer before transmitting data is also an example of connection-oriented protocol.
Not all connection-oriented protocols are reliable. For example, ATM and Frame Relay are two unreliable connection-oriented protocols. There are some connectionless yet reliable protocols such as AX.25 as well. However, this combination of reliable-connectionless is rare in commercial and academic networks.
Connection-oriented protocols are capable of handling real-time traffic more efficiently than connectionless protocols. This is the reason why ATM is still used for carrying real-time, isochronous traffic streams, especially in heavily aggregated networks like backbones.
Other examples of connection-oriented protocols are DCCP, TIPC, SCTP, Connection-oriented Ethernet, and IPX/SPX.
