摘要：There are several applicatio ns that require the data to be sent from a process running on a host to a process running on another host to be sent in a reliable manner even if the channel is unreliable. A channel is said to be unreliable if there are either bit errors or packet losses or both. In that case, the transport service needs to possess a mechanism for delivering segments from the sending process to the receiving process in a reliable manner. The mechanism often includes ackno wledgements and retransmissions. The Transmission Control Protocol (TCP) incorporates such a mechanism for reliable delivery of segments between two co mmunicating processes running on different hosts. In addition to such a mechanism, TCP provides a connection oriented service that includes mechanisms for flow control, congestion control, and in-order delivery of segments.
