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					Measurement of the Congestion
 Responsiveness of RealPlayer
  Streaming Video Over UDP

 Jae Chung, Mark Claypool, Yali Zhu
       Proceedings of the International
        Workshop on Packet Video (PV)
               Nantes, France
                April 2003
 http://www.cs.wpi.edu/~claypool/papers/h2h/
   The Hungry Wolf - Bandwidth
     Requirements for Video
• Streaming media growing
  – 350,000 hours of online video broadcast ’01
• Voice is 32-64 Kbps, but video has range of
  data rates
  – Videoconference 0.1 Mbps (H.261, MPEG-4)
  – VCR 1.2 Mbps (MPEG-1)
  – Broadcast quality 2-4 Mbps (MPEG-2)
  – HDTV quality 25-34 Mbps (MPEG-2)
   Thus, potential for more than network
    capacity
The Wolf on the Prowl – Transport
      Protocols for Video
• Streaming video doesn’t like TCP
  – Wants rate-based not window-based
  – Can tolerate some loss
  – AIMD causes rate fluctuations
  So, use UDP where application controls
• But UDP has no congestion control
  – Unfair, unfriendly, and even collapse!
• Approaches to have router catch
  – Model video as CBR “firehose” (is it?)
The Wolf Pack – Commercial Video

• Commercial products have major impact

• Have been studies characterizing
  commercial traffic
  – Bandwidth use, frame rate, user use…
• But no work measuring responsiveness, or
  lack of it, of commercial video products
                                  Specific Motivation
                         1
Cum m ulative Density
                                           TCP


                        0.8                UDP




                        0.6                            TCP
                        0.4                            UDP

                        0.2

                         0
                              0          10          20      30
                                        Fram e Rate (fps)
                 Outline

• Introduction     
• Background       
• Experiments
• Results
• Analysis
• Conclusions
  RealVideo Network Characteristics

                         RTSP


   Server
                    Data: TCP or UDP
                     -Choice, unclear
                       -We’ll force

• SureStream
  – Allows bandwidth scaling
• Buffering
  – Remove jitter
                 Outline

• Introduction     
• Background       
• Experiments      
• Results
• Analysis
• Conclusions
                Methodology

• Select Real Video Clips
• Construct environment for measuring
    congestion response
•   Construct environment to measure ability
    to scale (SureStream)
•   Iteratively plan clips varying network
           RealVideo Clip Playlist
• If put in controlled environment, may not
    be representative of clips “in the wild”
•   Select large number through search
    engines (Yahoo, Google …)
•   Randomly choose 100 (79 analyzed)
•   Geography results:
    – 76 US, 9 Canada, 8 UK, 6 Italy, 1 Germany
    – North American dominance likely reflected
      in typical user locality of reference
• Length results:
    – Median 3 minutes, min 20 seconds, max 30
      minutes
      Responsiveness Measurement
              Environment
          Client
    UDP                           Router

                   Hub
                                            DSL
          Client                           700Kbps
                   10Mbps                            Internet   Server
    TCP
                         Token Bucket Filter


•   PIII 700 Mhz, 128 MB RAM, Linux 2.4
•   RealPlayer version 8.0.3
•   Sniffing via tcpdump
•   Loss and round-trip time via ping
•   TBF to limit bandwidth
•   2 Measurements for each clip
•   (Note, RealTracer for MediaScaling)
                 Outline

• Introduction     
• Background       
• Experiments      
• Results          
• Analysis
• Conclusions
                               Distribution of Loss
                      1




                     0.8
Cumulative Density




                     0.6


                                                         075 Kbps
                                                         150 Kbps
                                                         300 Kbps
                     0.4                                 600 Kbps




                     0.2




                      0
                           0    0.05        0.1                 0.15   0.2
                                       Loss (fraction)
                                Distribution of Latency
                      1




                     0.8
Cumulative Density




                     0.6




                     0.4                                               075 Kbps
                                                                       150 Kbps
                                                                       300 Kbps
                                                                       600 Kbps


                     0.2




                      0
                           0   100   200   300    400        500      600     700   800   900
                                                 RTT (milliseconds)
                               Distribution of Packet Sizes
                      1




                     0.8
Cumulative Density




                     0.6




                     0.4




                     0.2                                                           TCP
                                                                                   UDP




                      0
                           0    200   400   600           800        1000   1200     1400   1600
                                                  Packet Size (Kbytes)
                       Outline
•   Introduction         
•   Background           
•   Experiments          
•   Results              
•   Analysis
    –   Head to Head     
    –   Bandwidth
    –   Scaling
    –   Buffering
    –   Smooth

•   Conclusions
                              RealPlayer = FairPlayer?
                    400



                    350                 Clip-19 TCP (DSL: BW = 600Kbps, Q = 10Kbytes)
                                        Clip-19 UDP (DSL: BW = 600Kbps, Q = 10Kbytes)


                    300


                    250
Throughput (Kbps)




                    200



                    150



                    100



                    50



                      0
                          0    50        100                 150             200        250
                                    Playout + Buffering Time (Seconds)
                              RealPlayer = FoulPlayer?
                    600



                                         Clip-31 TCP (DSL: BW = 600Kbps, Q = 10Kbytes)
                    500                  Clip-31 UDP (DSL: BW = 600Kbps, Q = 10Kbytes)




                    400
Throughput (Kbps)




                    300




                    200




                    100




                      0
                          0     50        100                 150             200        250
                                     Playout + Buffering Time (Seconds)
                                                  1
                                                                              Bandwidth Distribution
                                                                                                                                                                  1

                                              0.9
                                                                                                                                                                 0.9

                                              0.8
                                                                                                                                                                 0.8

                                              0.7
                                                                                                                                                                 0.7
                     Cumulative Density




                                                                                                                                            Cumulative Density
                                              0.6
                                                                                                           600 Kbps                                              0.6

                                              0.5
                                                                                                                                                                 0.5

                                              0.4
                                                                                                                                                                 0.4
                                                                                                                                                                                                                         300 Kbps
                                              0.3                                                                                                                0.3

                                              0.2                                                         Average Bandwidth for TCP                              0.2                                                 Average Bandwidth for TCP
                                                                                                          Average Bandwidth for UDP                                                                                  Average Bandwidth for UDP
                                              0.1                                                                                                                0.1

                                                  0                                                                                                               0
                                                      0        100             200            300               400             500                 600                0        50         100            150              200            250              300
                                                                             Average Bandwidth for 600 Kbps (Kbps)                                                                        Average Bandwidth for 300 Kbps (Kbps)
                                          1                                                                                                                       1


                      0.9                                                                                                                                        0.9


                      0.8                                                                                                                                        0.8


                      0.7                                                                                                                                        0.7
                                                                                                                                            Cumulative Density
Cumulative Density




                      0.6                                                                                                                                        0.6


                      0.5                                                                                                                                        0.5


                      0.4                                                                                  150 Kbps                                              0.4
                                                                                                                                                                                                                                  75 Kbps
                      0.3                                                                                                                                        0.3


                      0.2                                                                           Average Bandwidth for TCP                                    0.2                                                      Average Bandwidth for TCP
                                                                                                    Average Bandwidth for UDP                                                                                             Average Bandwidth for UDP

                      0.1                                                                                                                                        0.1


                                          0                                                                                                                       0
                                              0           20         40           60          80          100         120             140                              0   10        20            30           40           50           60          70
                                                                          Average Bandwidth for 150 Kbps (Kbps)                                                                            Average Bandwidth for 75 Kbps (Kbps)
                                             Head-to-Head Bandwidth
                                   400
                                                                                                  75 Kbps
                                                                                                 150 Kbps
                                                                                                 300 Kbps
                                   350                                                           600 Kbps



                                   300
Average Bandwidth for UDP (Kbps)




                                   250



                                   200



                                   150



                                   100



                                   50



                                     0
                                         0   50   100     150         200         250      300       350    400
                                                        Average Bandwidth for TCP (Kbps)
                      Bandwidth Difference Distribution
                      1




                     0.8
Cumulative Density




                     0.6




                     0.4




                     0.2

                                                                                                 75 Kbps
                                                                                                150 Kbps
                                                                                                300 Kbps
                                                                                                600 Kbps
                      0
                           -1   -0.8   -0.6      -0.4      -0.2        0        0.2       0.4        0.6   0.8
                                          Normalized Average Bandwidth Difference (TCP-UDP)
        Mostly TCP-Friendly!
• Remove low bandwidth (36%)
• Then remove unscalable (14%)
                     Outline
•   Introduction       
•   Background         
•   Experiments        
•   Results            
•   Analysis
    – Head to Head     
    – Bandwidth        
    – Scaling          
    – Buffering
    – Smooth

•   Conclusions
                               Media Scaling Distribution
                      1


                     0.9


                     0.8


                     0.7
Cumulative Density




                     0.6


                     0.5


                     0.4


                     0.3


                     0.2


                     0.1


                      0
                           1    2   3        4          5          6         7   8   9
                                        Number of Scales (Coded-Bandwidth)
Media Scales
                                     Media Scaling Dynamics (1)
                        250000

                                                                         local bw limit (35 kbps)
                                                     Scale (Coded-BW) Movement for Clip-65 TCP
                                                     Scale (Coded-BW) Movement for Clip-65 UDP
                        200000
Coded-Bandwidth (bps)




                        150000




                        100000




                         50000




                             0
                                 0     50   100         150           200           250         300   350
                                                  Playout + Buffereing Time (sec)
                                     Media Scaling Dynamics (2)
                        300000


                                                                         local bw limit (35 kbps)
                                                     Scale (Coded-BW) Movement for Clip-78 TCP
                        250000                       Scale (Coded-BW) Movement for Clip-78 UDP




                        200000
Coded-Bandwidth (bps)




                        150000




                        100000




                         50000




                             0
                                 0      20   40          60            80           100         120   140
                                                  Playout + Buffereing Time (sec)
                               Media Scaling Distributions
                      1


                     0.9


                     0.8


                     0.7
Cumulative Density




                     0.6


                     0.5


                     0.4


                     0.3


                     0.2                                 Number of Scale Changes Seen for TCP
                                                         Number of Scale Changes Seen for UDP

                     0.1


                      0
                           0      2             4                 6                 8           10
                                      Number of Scale (Coded-Bandwidth) Changes
                           Media Scaling Adaptation Speed
                      1


                     0.9


                     0.8


                     0.7
Cumulative Density




                     0.6


                     0.5


                     0.4


                     0.3


                     0.2                                         Scale Adaptation Speed for TCP
                                                                 Scale Adaptation Speed for UDP

                     0.1


                      0
                           0   10   20          30          40          50          60            70   80
                                    Elaps Time in Seconds: 0 to time(Coded-BW < 35kbps)
                     Outline
•   Introduction       
•   Background         
•   Experiments        
•   Results            
•   Analysis
    – Head to Head     
    – Bandwidth        
    – Scaling          
    – Buffering        
    – Smooth

•   Conclusions
                                                               Buffering Rate to Playout Rate
                                                       7
Average Buffering Rate / Average Steady Playout Rate




                                                       6                                                 TCP (All DSL-TBF Runs)
                                                                                                         UDP (All DSL-TBF Runs)


                                                       5



                                                       4



                                                       3



                                                       2



                                                       1



                                                       0
                                                           0      50   100      150         200         250        300        350   400
                                                                             Average Steady Playout Rate (Kbps)
                       Buffering Rate to Playout Rate
                                Distribution
                      1




                     0.8
Cumulative Density




                     0.6




                     0.4




                     0.2                                                   TCP (All LAN Runs)
                                                                           UDP (All LAN Runs)




                      0
                           0   1       2             3             4             5              6   7
                                   Average Buffering Rate / Average Steady Playout Rate
                                       Smoothness
                      1
                           TCP
                           UDP
                     0.9


                     0.8


                     0.7
Cumulative Density




                     0.6


                     0.5


                     0.4


                     0.3


                     0.2


                     0.1


                      0
                                 1/2             1           2
                                          Throughput Ratio
                                                              Smoothness at each Bottleneck
                                              1                                                                             1
                                                  TCP                                                                            TCP
                                                  UDP                                                                            UDP
                                          0.9                                                                              0.9

                                          0.8                                                                              0.8

                                          0.7                                                                              0.7
                     Cumulative Density




                                                                                                      Cumulative Density
                                          0.6
                                                                                                                           0.6

                                          0.5
                                                                                                                           0.5

                                          0.4
                                                                                                                           0.4

                                          0.3
                                                                                                                           0.3

                                          0.2
                                                                                                                           0.2

                                          0.1
                                                                                                                           0.1
                                              0
                                                         1/2                   1                  2                         0
                                                                  Throughput Ratio for 600 Kbps                                        1/2                1                  2
                                                                                                                                             Throughput Ratio for 300 Kbps
                                                                                                                            1
                                          1                                                                                      TCP
                                              TCP                                                                                UDP
                                              UDP                                                                          0.9
                                      0.9

                                                                                                                           0.8
                                      0.8


                                      0.7
                                                                                                      Cumulative Density   0.7
Cumulative Density




                                      0.6                                                                                  0.6


                                      0.5                                                                                  0.5


                                      0.4                                                                                  0.4


                                      0.3                                                                                  0.3


                                      0.2                                                                                  0.2

                                      0.1                                                                                  0.1

                                          0                                                                                 0
                                                        1/2                   1                   2
                                                                                                                                       1/2                1                      2
                                                                 Throughput Ratio for 150 Kbps
                                                                                                                                              Throughput Ratio for 75 Kbps
           Discussion of Results
• No concrete incentives to respond to
    congestion
    – In fact, may be “rewarded” for not
• However, RealVideo clearly responds
    – Often TCP-Friendly
• Content providers need to provide chance
    for scalability
    – Scaling levels
• But buffering at higher rate is bad for
    network
•   TCP can be as smooth as UDP
•   So why not TCP?  API is limiting
Future Work?
                 Future Work

• Other commercial Players
    – Microsoft Media Player
• Live clips (versus pre-recorded clips)
• Perceptual quality of video over TCP versus
    UDP
•   Characterization of clips on Internet
    – So can examine “typical” clips

				
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posted:12/8/2010
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