Best effort delivery

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Best effort delivery describes a network service in which the does not provide any special features that recover lost or corrupted data. By removing the need to provide these services, the network operates more efficiently.

The postal service delivers letters using a best effort delivery approach. The sender isn't informed if a letter has been delivered successfully. However, the sender can pay extra for a delivery confirmation receipt, which requires that the carrier get a signature from the recipient to prove the successful delivery.

In a very similar way, the best effort delivery is implemented in the Short Message Service. Since there are thousands of subscribers per operator, the messages need to be delivered efficiently, quickly, and with minimum of expense. The network operator will make its "best effort" to try to deliver a message, but if the process somehow fails (due to network instability, poor reception, or computer error), the message is simply lost, and the sender won't know to re-send it.

In the TCP/IP protocol suite, TCP provides guaranteed services while UDP provides best effort delivery. TCP verifies that all information transmitted is received fully on the other end. UDP does its best to deliver packets to the destination, but takes no steps to recover packets that are lost or misdirected. The more stable TCP protocol is often used to deliver data like web pages and email, while UDP is reserved for media streaming or network gaming.

Book sources

Encyclopedia of Networking & Telecommunications ISBN 0072120053

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