Measurement and Performance Study of PERT for On-demand Video - PowerPoint PPT Presentation

Introduction Background Experiment Summary Back-up Measurement and Performance Study of PERT for On-demand Video Streaming Bin Qian A.L.Narasimha Reddy Department of ECE Texas A&M University PFLDNeT 2010

Introduction Background Experiment Summary Back-up Outline Introduction 1 Background 2 Experiment 3 NS2 Simulation Linux Test Summary 4

Introduction Background Experiment Summary Back-up Motivation Current TCP is not suitable for video streaming applications. In the Internet, many other services (HTTP , FTP , P2P) compete for bandwidth.

Introduction Background Experiment Summary Back-up Related Work . . . Boyden et al, 2007 TCP can function adequately with a 1.5 higher bandwidth than required stream rate in unconstrained streaming. Wang et al, 2008 TCP generally provides good streaming performance when the achievable TCP throughput is roughly twice the media bitrate, with only a few seconds of startup delay.

Introduction Background Experiment Summary Back-up Problem How well can TCP support streaming, when T/ µ ≤ 2.0? T is the achievable TCP throughput. µ is the video playback bitrate.

Introduction Background Experiment Summary Back-up Previous Work . . . PERT = Probabilistic Early Response TCP Sumitha et al, 2007 explored the performance of PERT in homogeneous environment. Kiran et al, 2008 made PERT adaptive to heterogeneous environments.

Introduction Background Experiment Summary Back-up Probabilistic Early Response PERT learns about network congestion by measuring delay

Introduction Background Experiment Summary Back-up Window Adjustment Mechanism ... Aggressive Window Increasing W = W + α α ≥ 1

Introduction Background Experiment Summary Back-up Window Adjustment Mechanism ... 3 modes T compete = 0 . 65 * maximum queuing delay When T < T min , high-speed mode When T > T compete , TCP-compete mode When T min < T < T compete , safe mode

Introduction Background Experiment Summary Back-up Window Adjustment Mechanism ... High-speed mode α = α max = 32 TCP-compete mode α = 1 + p ′ / p p ′ is the early response probability p is the congestion loss probability Safe mode α = α min = 1

Introduction Background Experiment Summary Back-up Window Adjustment Mechanism Conservative Window Decreasing W = W × ( 1 − β ) β = q ′ / ( q ′ + q ) q ′ is the estimated queuing delay q is the maximum queuing delay so W ≥ W / 2

Introduction Background Experiment Summary Back-up Queuing Behavior PERT enqueues more packet earlier and less later ... Frequency vs. Queue Position 100000 PERT TCP 10000 1000 Frequency 100 10 1 0 200 400 600 800 1000 1200 Queue Position

Introduction Background Experiment Summary Back-up NS2 Simulation Setup

Introduction Background Experiment Summary Back-up NS2 Simulation Parameters Exploration T/u vs. CBR Streams Number Bandwidth vs. CBR Streams Number 2.4 32.5 CBR 2.2 30.0 FTP HTTP 27.5 2.0 25.0 1.8 Bandwidth (Mbits) 22.5 1.6 20.0 1.4 17.5 T/u 1.2 15.0 1.0 12.5 10.0 7.5 5.0 21 23 26 30 34 21 23 26 30 34 CBR Streams Number CBR Streams Number

Introduction Background Experiment Summary Back-up NS2 Simulation Performance Metric CBR stream is successful if fraction of late packets < 10 − 4 Video streaming quality is evaluated by fraction of successful CBR streams

Introduction Background Experiment Summary Back-up NS2 Simulation Simulation Results . . . In low range [1.0-1.4], it drops drastically as T/ µ decreases In high range [1.4-2.0], it changes slightly as T/ µ increases Fraction of Successful CBR Streams vs. T/u Fraction of Successful CBR Streams (%) PERT 110 RENO 200 200 200 1000 1000 1000 200 100 CUBIC 1000 90 80 70 60 50 40 30 20 200 10 1000 0 1.0-1.2 1.2-1.4 1.4-1.6 1.6-1.8 1.8-2.0 T/u (Start-up Delay 10 secs)

Introduction Background Experiment Summary Back-up NS2 Simulation Simulation Results . . . PERT > RENO and CUBIC in T/ µ range [1.0 - 1.4] Fraction of Successful CBR streams vs. Start-up Delay Fraction of Successful CBR streams vs. Start-up Delay 25 120 RENO RENO PERT PERT Fraction of Successful CBR streams (%) Fraction of Successful CBR streams (%) CUBIC CUBIC 20 100 15 80 10 60 5 40 0 20 � 5 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 Start-up Delay (secs) ( T/u 1.0-1.2, Loss Rate 0.056 ) Start-up Delay (secs) ( T/u 1.2-1.4, Loss Rate 0.045 )

Introduction Background Experiment Summary Back-up NS2 Simulation Simulation Results . . . PERT > RENO & PERT ≈ CUBIC in T/ µ range [1.4 - 1.8] Fraction of Successful CBR streams vs. Start-up Delay Fraction of Successful CBR streams vs. Start-up Delay 110 105 Fraction of Successful CBR streams (%) Fraction of Successful CBR streams (%) 100 100 95 90 90 80 85 70 80 60 RENO RENO 75 PERT PERT CUBIC CUBIC 50 70 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 Start-up Delay (secs) ( T/u 1.4-1.6, Loss Rate 0.034 ) Start-up Delay (secs) ( T/u 1.6-1.8, Loss Rate 0.030 )

Introduction Background Experiment Summary Back-up NS2 Simulation Simulation Results PERT > RENO and CUBIC in loss rate range [0.02 - 0.06] Fraction of Successful CBR streams vs. Start-up Delay Fraction of Successful CBR streams vs. Start-up Delay 100 90 Fraction of Successful CBR streams (%) Fraction of Successful CBR streams (%) 95 80 90 70 85 60 80 50 75 40 70 RENO RENO 30 65 PERT PERT CUBIC CUBIC 60 20 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 Start-up Delay (secs) ( Loss Rate 0.02-0.04, T/u 1.68) Start-up Delay (secs) ( Loss Rate 0.04-0.06, T/u 1.26)

Introduction Background Experiment Summary Back-up Linux Test Test Bed Bandwidth 15 Mbps Delay 45 ms Buffer 500 Kb Avatar 1080p HTTP streaming

Introduction Background Experiment Summary Back-up Linux Test Test Results . . . PERT helps to reduce the playback glitches TCP Variants PERT RENO CUBIC Late Picture Skipping # 5.5 33.5 30.5 Audio Output Starving # 3.0 11.0 7.5

Introduction Background Experiment Summary Back-up Linux Test Test Results PERT responses early before packet loss. PERT adjusts the window smoothly. CWND Size vs. Time 180 PERT RENO 160 CUBIC 140 CWND Size (Mbytes) 120 100 80 60 40 20 0 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 Time (0.01s)

Introduction Background Experiment Summary Back-up Conclusions PERT and CUBIC push T/ µ constraint to roughly 1.4. PERT > RENO, over all T/ µ s, loss rates and start-up delays. PERT > CUBIC, over low T/ µ s, high loss rates and strict start-up delays constraints.

Introduction Background Experiment Summary Back-up Future Work Carry out more evaluations and comparisons against other protocols. Deploy and measure PERT in error-prone wireless networks.

Introduction Background Experiment Summary Back-up Thank You !

Introduction Background Experiment Summary Back-up Probabilistic Early Response Parameters The parameters are currently fixed, and can be chosen adaptively T min = 5 ms T max = 10 ms P max = 0 . 05

Introduction Background Experiment Summary Back-up α adjustment Steady state throughput equations: β PERT ( p + p ′ − p ∗ p ′ ) /α PERT = β TCP ∗ p /α TCP α TCP = 1 β PERT = β TCP So α PERT = p + p ′ − p ∗ p ′ / p ≈ 1 + p ′ / p