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Prof. Dr.-Ing. Jochen Schiller, MC SS059.1Mobile Communications Chapter 9: Mobile Transport LayerMotivationTCP-mechanismsClassical approachesIndirect TCPSnooping TCPMobile TCPPEPs in generalAdditional optimizationsFast retransmit/recoveryTransmission freezingSelective retransmissionTransaction oriented TCPTCP for 2.5G/3G wireless
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Prof. Dr.-Ing. Jochen Schiller, MC SS059.2Transport LayerE.g. HTTP (used by web services) typically uses TCPReliable transport between client and server requiredTCPSteam oriented, not transaction orientedNetwork friendly: time-out Îcongestion Îslow down transmissionWell known – TCP guesses quite often wrong in wireless and mobile networksPacket loss due to transmission errorsPacket loss due to change of networkResultSevere performance degradationClientServerConnectionsetupDatatransmissionTCP SYNTCP SYN/ACKTCP ACKHTTP requestConnectionreleaseHTTP responseGPRS: 500ms!>15 sno data