Internet Core Protocols: The Definitive Guide

Limited reliability

Although applications that broadcast information on a frequent basis have to use UDP, they do gain some benefits from doing so. Since broadcasts are sent to every device on the local network, it would take far too long for the sender to establish individual TCP connections with every other system on the network, exchange data with them all, and then disconnect. Conversely, UDP’s connectionless service allows the sender to simply send the data to all of the devices simultaneously. If any of the systems do not receive one of the messages, then they will likely receive one of the next broadcasts, and as such will not be substantially harmed by missing one or two of them.

Furthermore, streaming applications (such as real-time audio and video) can also benefit from UDP’s low-overhead structure. Since these applications are stream-oriented, the individual messages are not nearly as important as the overall stream of data. The user will not notice if a single IP packet gets lost every so often, so it is better to just continually keep sending the next message, rather than stopping everything to resend a single message. These applications actually see error-correction as a liability, so UDP’s connectionless approach is a “feature” rather than a “problem.”

Similarly, any application that needs only a lightweight query and response service would be unduly burdened by TCP’s connection-oriented services and would benefit from UDP’s low overhead. Some database and network-lookup ...