TCP also includes a congestion-control mechanism, a service for the general welfare of the Internet rather than for the direct benefit of the communicating processes. The TCP congestion-control mechanism throttles a sending process (client or server) when the network is congested between sender and receiver. As we will see in Chapter 3, TCP congestion control also attempts to limit each TCP connection to its fair share of network bandwidth. The throttles of the transmission rate can have a very harmful effect on real-time audio and video applications that have minimum throughput requirements. Moreover, real-time applications are loss-tolerant and do not need a fully reliable transport service. For these reasons, developers of real-time applications often choose to run their applications over UDP rather than TCP.