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Eifel Retransmission Timer Implementation

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

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Eifel Retransmission Timer Implementation

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  1. Eifel Retransmission Timer Implementation Seth A. Hellbusch University of California – Santa Cruz CMPE 257 – Wireless & Mobile Networks Winter 2011

  2. 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

  3. Lite RTO vs. Eifel RTO

  4. Initial Testing Model • Wrote two OO BASIC macros to auto-populate/calculate • runTCPlite & runTCPeifel Authors’ Model My Model

  5. 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

  6. Simulation Scenario Focused on Flow 1

  7. Qualnet Analysis Results

  8. 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

  9. Questions

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