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Hybrid Testbed Case Studies

Impact of wide range of bandwidth and delay values on wired portion of wired-cum-wireless scenario ... Stationary wireless hosts accessing Internet via UCSD CDMA2000 base ...

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Hybrid Testbed Case Studies

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    Slide 1:Hybrid Testbed Case Studies

    Mahesh Marina

    Slide 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

    Slide 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

    Slide 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)

    Slide 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)

    Slide 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

    Slide 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 Note: XCP – A cross-layer adaptation mechanism spanning transport, network and link/MAC layers (with addition of bandwidth estimation support) Note: XCP – A cross-layer adaptation mechanism spanning transport, network and link/MAC layers (with addition of bandwidth estimation support)

    Slide 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)

    Slide 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 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 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

    Slide 10:Congestion Window Dynamics (Emulation)

    Slide 11:Congestion Window Dynamics (Simulation)

    Slide 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

    Slide 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

    Slide 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)

    Slide 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

    Slide 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

    Slide 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)

    Slide 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 Measurement data; demo?Measurement data; demo?

    Slide 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)

    Slide 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

    Slide 21:TCP Throughput

    Slide 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)

    Slide 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 AR1 AR2 AR: Access Router DemoDemo

    Slide 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) DemoDemo

    Slide 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

    Slide 26:SCTP Throughput Over Physical Wireless Link

    Slide 27:After Disabling Physical Link…

    Slide 28:SCTP Switches to Emulated Wireless Link…

    Slide 29:On Re-Enabling Physical Link…

    Slide 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

    Slide 31:Accessibility

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