EIFEL RETRANSMISSION TIMER IMPLEMENTATION Seth A Hellbusch University of California Santa Cruz CMPE 257 Wireless Mobile Networks Winter 2011 Eifel Retransmission Timer Proposed by R Ludwig K Sklower 2000 Comparison between TCP Lite TCP Eifel Retransmission Timeout Value RTO Elapsed time since packet is sent Upper limit of RTT RTO packet REXMT TCP Lite RTO weaknesses Prediction flaw when RTT drops Failure of estimator gains REXMT restart bug Timer granularity TCP Eifel RTO address these issues Lite RTO vs Eifel RTO Initial Testing Model Wrote two OO BASIC macros to auto populate calculate runTCPlite runTCPeifel Authors Model My Model Qualnet Implementation Source files transport tcp input cpp RTT sampling SRRT RTTVAR REXMT transport tcp timer cpp Heartbeat timer REXMT updates transport tcp output cpp TCP transmit Statistics capture note all files located in qualnet 4 0 libraries developer src Test Network Two Qualnet Branches Control Experiment Traditional TCP IP bottleneck Wireless with multiple subnets Multiple TCP flows FTP Increase channel utilization Monitored single flow One flow across two routers Captured output statistics Monitored input computations Simulation Scenario Focused on Flow 1 Qualnet Analysis Results TCP Lite 12 30000 10 25000 8 20000 6 15000 4 10000 2 5000 0 rxcur srtt rttvar cwnd TX Packet cwnd rxtcur srtt rttvar 0 50 100 150 200 250 TCP Eifel 45 40 35 30 25 20 15 10 5 0 30000 25000 20000 15000 10000 5000 0 50 100 150 200 250 rxcur srtt rttvar cwnd TX Packet cwnd rxtcur srtt rttvar Conclusion Success Spreadsheet model Matched authors work from scratch Dynamic data generation and analysis TCP Lite RTO TCP Eifel RTO TCP Light Flow Capture in Qualnet Qualnet TCP Eifel RTO Works Follows current data in flight Transmitted data is the same per time Challenges Valid Experiment Model Counter Binary Math TCP Congestion Window Questions
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