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Hybrid Testbed Case Studies

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  • Note: XCP – A cross-layer adaptation mechanism spanning transport, network and link/MAC layers (with addition of bandwidth estimation support)
  • Settings: Large XCP/TCP buffer (640KB), max queue length (default = 100), MAC data rate (11Mbps), no delayed acks, no SACK, MTU (512 bytes), no wireless losses
  • Measurement data; demo?
  • Demo
  • Demo
  • Transcript

    • 1. Hybrid Testbed Case Studies Mahesh Marina
    • 2. Hybrid Testbed
      • Embodies benefits of real experimentation, simulation and emulation in a single evaluation framework
      • Provides ability to integrate real, simulated and emulated components seamlessly
      Simulation Scalability Repeatability Configurability Physical Realism Emulation Real applications & protocols Repeatability
    • 3. Hybrid Testbed Case Studies
      • To demonstrate hybrid testbed:
        • Value for realistic and scalable experimentation wireless network experimentation
        • Flexibility in choosing appropriate experimentation mode depending on evaluation needs and available resources
        • Usefulness for a broad range of interesting wireless networking scenarios
          • Study of cross-layer interactions and adaptation mechanisms
          • Evaluation of heterogeneous wireless network scenarios
    • 4. Overview
      • Cross-layer interactions and adaptation mechanisms
        • Cross-layer transport protocol (XCP) performance in wireless networks ( emulation )
          • Collaboration between UCLA (R. Bagrodia, M. Gerla) and HRL Labs (Y. Zhang)
        • Evaluation of adaptive video streaming applications (QStream) in mobile ad hoc networks ( emulation and simulation )
      • Heterogeneous wireless networking scenarios
        • Bandwidth aggregation via multi-homed wireless hosts in inter-working cellular and mesh networks ( physical, emulation and simulation )
          • Collaboration between UCLA (R. Bagrodia) and UCSD (R. Rao)
        • Internet host mobility support using SCTP ( physical and emulation )
          • Collaboration between UCLA (R. Bagrodia) and Univ. of Delaware (C. Shen)
    • 5. Overview
      • Cross-layer interactions and adaptation mechanisms
        • Cross-layer transport protocol (XCP) performance in wireless networks ( emulation )
          • Collaboration between UCLA (R. Bagrodia, M. Gerla) and HRL Labs (Y. Zhang)
        • Evaluation of adaptive video streaming applications (QStream) in mobile ad hoc networks ( emulation and simulation )
      • Heterogeneous wireless networking scenarios
        • Bandwidth aggregation via multi-homed wireless hosts in inter-working cellular and mesh networks ( physical, emulation and simulation )
          • Collaboration between UCLA (R. Bagrodia) and UCSD (R. Rao)
        • Internet host mobility support using SCTP ( physical and emulation )
          • Collaboration between UCLA (R. Bagrodia) and Univ. of Delaware (C. Shen)
    • 6. eXplicit Control Protocol (XCP) (Katabi et al, Sigcomm 2002)
      • A recent proposal with better efficiency, stability and fairness over wired/satellite links relative to TCP
      • Uses precise network feedback along with decoupled congestion and fairness control
      S D R 1 R n End host Router ACK DATA Congestion Window Round Trip Time Feedback Congestion Header DATA Congestion Window Round Trip Time Feedback= +1pkt Congestion Header DATA Congestion Window Round Trip Time Feedback= -2pkt Congestion Header DATA Congestion Window Round Trip Time Feedback= -2pkt Congestion Header ACK Congestion window += feedback Congestion controller: Aggregate feedback = f ( available bandwidth , queue size) Fairness controller: Divides total feedback between flows fairly
    • 7. XCP over Wireless
      • Error control decoupled from rate control because of precise feedback
        • Can identify non-congestion losses since congestion losses negligible
      • Allows operation in congestion avoidance phase, efficient in presence of failures
      • Support for service differentiation via flexible bandwidth allocation
      • Relies on available bandwidth estimation for accurate feedback calculation
      • Accurate available bandwidth estimation challenging in wireless networks due to medium access contention and lossy links (Padmanabhan et al, IMC 2004)
        • Heavily depends on MAC (efficiency and fairness), channel and traffic characteristics
    • 8. XCP Performance in Wireless Networks
      • Evaluate XCP performance in both wireless LAN and multi-hop wireless scenarios with various bandwidth estimation techniques
      • Hybrid testbed usage – emulated wireless network integrated with the physical Internet
      • Collaboration between UCLA (R. Bagrodia, M. Gerla) and HRL Labs (Y. Zhang)
    • 9.
      • Discrepancy in throughput behavior between emulation and simulation results due to system effects
      • In a real system, read and write events between NIC and OS share same CPU and memory resources
        • Steady ACK flow limits traffic injection rate despite large feedback from capacity overestimation
      • XCP (TCP) cannot overflow its own device
        • Self-throttling behavior at source inspite of large and erroneous network feedback
      • Emulation can realistically capture the impact of system effects on protocol performance, while being repeatable
      XCP Performance with Bandwidth Estimation Errors Single 802.11 Wireless Link NS-2 Simulation Emulation
    • 10. Congestion Window Dynamics (Emulation)
    • 11. Congestion Window Dynamics (Simulation)
    • 12. XCP Performance with Bandwidth Estimation Errors Infrastructure Wireless LAN Internet
      • Impact of capacity estimation errors depends on the location of bottleneck link on the path
      Wired path (1Gb bandwidth, 50ms round-trip propagation delay) emulated using NIST Net Download Upload 1500 byte MTU Wireless link (802.11b, 11Mb fixed PHY data rate) emulated
    • 13. On-Going Work
      • Impact of wide range of bandwidth and delay values on wired portion of wired-cum-wireless scenario
      • Impact of inter-flow multiple access interference and interaction with fairness issue
      • Impact of packet loss due to fading
      • Comparison of various dynamic bandwidth estimation techniques
      • Comparison of XCP and TCPW
    • 14. Overview
      • Cross-layer interactions and adaptation mechanisms
        • Cross-layer transport protocol (XCP) performance in wireless networks ( emulation )
          • Collaboration between UCLA (R. Bagrodia, M. Gerla) and HRL Labs (Y. Zhang)
        • Evaluation of adaptive video streaming applications (QStream) in mobile ad hoc networks ( emulation and simulation )
      • Heterogeneous wireless networking scenarios
        • Bandwidth aggregation via multi-homed wireless hosts in inter-working cellular and mesh networks ( physical, emulation and simulation )
          • Collaboration between UCLA (R. Bagrodia) and UCSD (R. Rao)
        • Internet host mobility support using SCTP ( physical and emulation )
          • Collaboration between UCLA (R. Bagrodia) and Univ. of Delaware (C. Shen)
    • 15. Adaptive Video Streaming Performance in Ad Hoc Networks
      • Evaluate adaptive video streaming performance in presence of channel fading, congestion and node mobility in ad hoc networks
      • Use QStream as a representative adaptive media application
        • Optimizes two quantitative measures of video quality along temporal and spatial dimensions
        • Relies on TCP for rate control and drops low priority data during congestion to maintain video quality and timeliness
    • 16. Adaptive Video Streaming Performance in Ad Hoc Networks
      • Hybrid testbed usage – emulated wireless hosts running QStream communicating with each other over a simulated ad hoc network
      • Observed complete lack of correlation between perceptual and quantitative metrics , especially with node mobility
    • 17. Overview
      • Cross-layer interactions and adaptation mechanisms
        • Cross-layer transport protocol (XCP) performance in wireless networks ( emulation )
          • Collaboration between UCLA (R. Bagrodia, M. Gerla) and HRL Labs (Y. Zhang)
        • Evaluation of adaptive video streaming applications (QStream) in mobile ad hoc networks ( emulation and simulation )
      • Heterogeneous wireless networking scenarios
        • Bandwidth aggregation via multi-homed wireless hosts in inter-working cellular and mesh networks ( physical, emulation and simulation )
          • Collaboration between UCLA (R. Bagrodia) and UCSD (R. Rao)
        • Internet host mobility support using SCTP ( physical and emulation )
          • Collaboration between UCLA (R. Bagrodia) and Univ. of Delaware (C. Shen)
    • 18. Bandwidth Aggregation in Hybrid Cellular & Mesh Networks
      • Using existing cellular infrastructure to complement mesh networks via bandwidth aggregation at end hosts can provide more effective solution in terms of capacity, coverage and cost
      • Evaluate the effectiveness of network layer approach for bandwidth aggregation, using a combination of mechanisms for finding bandwidth availability, mitigating packet reordering and RTT variations
      Internet 3G Cellular Network WiFi Mesh Network
    • 19. Bandwidth Aggregation in Hybrid Cellular & Mesh Networks
      • Hybrid testbed usage – multi-homed wireless host connected to physical Internet via an emulated 802.11 interface to simulated mesh network as well as a real cellular link to CDMA 2000 base station (UCSD)
      • Tested the feasibility of this scenario via integration of hybrid testbed with CDMA 2000 testbed at UCSD
      • Collaboration between UCLA (R. Bagrodia) and UCSD (R. Rao)
    • 20. UCSD CDMA2000 Testbed Measurements
      • Stationary wireless hosts accessing Internet via UCSD CDMA2000 base station
      • Samples taken at three hosts at different sites in the BSC coverage area
      • Application: download three large image objects using HTTP
      • Measurements taken using Ethereal and Ericsson TEMS Investigation (air interface test tool) for a duration of ~5 minutes
      • No interference from other users
      • Impact of high spatio-temporal channel variations and link adaptation (power control, rate adaptation) on TCP throughput performance
    • 21. TCP Throughput
    • 22. Overview
      • Cross-layer interactions and adaptation mechanisms
        • Cross-layer transport protocol (XCP) performance in wireless networks ( emulation )
          • Collaboration between UCLA (R. Bagrodia, M. Gerla) and HRL Labs (Y. Zhang)
        • Evaluation of adaptive video streaming applications (QStream) in mobile ad hoc networks ( emulation and simulation )
      • Heterogeneous wireless networking scenarios
        • Bandwidth aggregation via multi-homed wireless hosts in inter-working cellular and mesh networks ( physical, emulation and simulation )
          • Collaboration between UCLA (R. Bagrodia) and UCSD (R. Rao)
        • Internet host mobility support using SCTP ( physical and emulation )
          • Collaboration between UCLA (R. Bagrodia) and Univ. of Delaware (C. Shen)
    • 23. SCTP for Internet Host Mobility Support
      • Dynamic address reconfiguration (DAR) and multi-homing features of SCTP enable seamless mobility support at transport layer
      • Evaluate SCTP handoff performance with image and audio (VoIP) applications using perceptual and quantitative metrics in scenarios involving wireless access networks and Internet
      Wired Internet Wireless Access Network AR 1 AR 2 AR: Access Router
    • 24. SCTP for Internet Host Mobility Support
      • Hybrid testbed usage – emulated multi-homed mobile host communicating with a physical correspondent host on Internet via a simulated multi-hop wireless access network
      • Use new testbed capabilities
        • Interoperation of distributed testbeds
        • Mobility emulation
        • Emulation of multi-homed hosts
      • Collaboration between UCLA (R. Bagrodia) and Univ. of Delaware (C. Shen)
    • 25. SCTP Demo ( http://chenyen.cs.ucla.edu/projects/whynet/SCTPDemo/ )
      • Demonstrate interoperation of distributed testbeds, and SCTP built-in multi-homing support and dynamic address reconfiguration features
      • By default, only physical link enabled initially
      Univ. Delaware UCLA
    • 26. SCTP Throughput Over Physical Wireless Link
    • 27. After Disabling Physical Link…
    • 28. SCTP Switches to Emulated Wireless Link…
    • 29. On Re-Enabling Physical Link…
    • 30. Summary
      • Several on-going collaborative case studies to show hybrid testbed utility for wireless network research
        • cross-layer studies, heterogeneous and/or large-scale wireless network scenarios
      • Obtain benefits of different experimentation modes
        • Emulation
          • Realistic evaluation of adaptive applications and protocols
          • Capture the impact of system effects on protocol performance
          • Repeatable and efficient (real-time) evaluation
        • Real experimentation
          • Real-world performance studies, characterization studies
          • No modeling costs
          • Real-time evaluation
        • Simulation
          • Scalable and real-time evaluation when combined with emulation or real experimentation
          • Evaluate future networking and radio technologies and assess potential of research ideas at early stages
    • 31. Accessibility

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