Abstract

As a reliable, end-to-end transport protocol, the Transmission Control Protocol (TCP) uses positive acknowledgements and retransmission to guarantee delivery. TCP implementations are expected to measure and adapt to changing round-trip delay so that their retransmission behavior balances user throughput and network efficiency. However, TCP suffers from a problem we call retransmission ambiguzty: when an acknowledgement arrives for a datagram that has been retransmitted, there is no indication of which transmission is being acknowledged. As a result, an implementation maybe unable to determine if the round-trip time it measures is for an original transmission or a retransmission of a datagram. Many existing TCP implementa-tions do not handle this problem correctly. Furthermore, the problem of retransmission ambigu-ity is also a characteristic of other major transport protocols, including 0S1 TP4 and DECnet NSP This paper reviews the various approaches to retransmission and presents a novel and effective approach to the retransmission ambiguity problem. Categories and Subject Descriptors: C 20 [Computer Communications Networks]: General—open System Interconnection reference model (0S1); C.2. 1 [Computer Communications Networks]: Network Architecture and Design—packet networks, store and forward net-works; D.4.4 [Operating Systems]: Communications Management — message sending, network communication

Citations