Collaborative computing/Connection-oriented vs. connectionless service

Connection-oriented and connectionless services are two distinct techniques in data communications to transfer data through a subnet. Both techniques have each its advantages and disadvantages.

A Connection-oriented service need to establish a session connection before data packages/frames can be sent. Using this method, guarantees that data will arrive in the same order as it was sent. An example of a connection-oriented service is the telephone network. A caller must dial the called party’s number and wait for the session connection to be established before talking or sending data. When the connection has been established a fixed route through the telephone system is maintained until the call is terminated. All data packages are sent through the same route. If something on the subnet goes down, the connection session is aborted.

A connectionless service does not need to establish a session connection before sending data packages/frames. Unlike with a connection-oriented service, every package is routed independently through the subnet. The advantage of this kind of connection service is that if something goes wrong on the subnet, no harm is done to the data which has already been sent. The network will simply reconfigure itself dynamically and the following data will be sent via a different route to the same destination. Using a connectionless service does not guarantee that the data is received in the same order as it was sent. An example of a connectionless service is the postal system.

Connection-oriented and connectionless services can either be reliable or unreliable.

Tanenbaum, A. & Wetherall, D. (2011) “Computer Networks”, 5th edition, Prentice hall, s. 35-38, 359-361