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
  • Hybrid Testbed Case Studies

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

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