C09-Transport_Protocols - Mobile Communications Chapter 9...

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Prof. Dr.-Ing. Jochen Schiller, MC SS05 9.1 Mobile Communications Chapter 9: Mobile Transport Layer Motivation TCP-mechanisms Classical approaches Indirect TCP Snooping TCP Mobile TCP PEPs in general Additional optimizations Fast retransmit/recovery Transmission freezing Selective retransmission Transaction oriented TCP TCP for 2.5G/3G wireless
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Prof. Dr.-Ing. Jochen Schiller, MC SS05 9.2 Transport Layer E.g. HTTP (used by web services) typically uses TCP Reliable transport between client and server required TCP Steam oriented, not transaction oriented Network friendly: time-out Î congestion Î slow down transmission Well known – TCP guesses quite often wrong in wireless and mobile networks Packet loss due to transmission errors Packet loss due to change of network Result Severe performance degradation Client Server Connection setup Data transmission TCP SYN TCP SYN/ACK TCP ACK HTTP request Connection release HTTP response GPRS: 500ms! >15 s no data
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