Eifel Retransmission Timer Implementation
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EIFEL RETRANSMISSION TIMER IMPLEMENTATION Seth A. Hellbusch University of California – Santa Cruz CMPE 257 – Wireless & Mobile Networks Winter 2011
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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 - PowerPoint PPT Presentation
Transcript of Eifel Retransmission Timer Implementation
EIFEL RETRANSMISSION TIMER IMPLEMENTATIONSeth A. HellbuschUniversity of California – Santa CruzCMPE 257 – Wireless & Mobile NetworksWinter 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
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TCP-Lite
cwndrxtcursrttrttvar
TX Packet
rxcu
r, sr
tt, rt
tvar
cwnd
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1015202530354045
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TCP-Eifel
cwndrxtcursrttrttvar
TX Packet
rxcu
r, sr
tt, rt
tvar
cwnd
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
