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End-to-End Analysis of Distributed Video-on-Demand Systems. Padmavathi Mundur, Robert Simon, and Arun K. Sood IEEE Transactions on Multimedia, February 2004. Outline. Motivation Hierarchical VoD architecture Analytical model Evaluation methodology and results Conclusion. Motivation.
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End-to-End Analysis of Distributed Video-on-Demand Systems Padmavathi Mundur, Robert Simon, and Arun K. Sood IEEE Transactions on Multimedia, February 2004
Outline • Motivation • Hierarchical VoD architecture • Analytical model • Evaluation methodology and results • Conclusion
Motivation • In a real environment, if a video requires R mbps transmission rate, allocate R mbps bandwidth is not accurate enough • From network view, analyze the bandwidth required for videos
Data flow at server Double buffer technique RSVP
Disk scheduling and double buffer scheme in the server Token bucket + WFQ 1. RAID-5 storage 2. SCAN EDF scheduling (RSVP) 2 7 6 1 4 5 3
packets packets wait r pkts/sec send pkts to network Traffic regulator at server (1/2) • Leaky bucket • Control average rate
r tokens/sec buckets holds up to b tokens packets packets wait remove token to network Traffic regulator at server (2/2) • Token Bucket • Control average rate • Control input burst size
Weighted fair queuing (WFQ) at server • Provide different priority to different packets
Token bucket scheme controls the average output rate WFQ allocates different resource to different users Token bucket + WFQ provide delay upper bound Combine token bucket & WFQ
Review the whole data flow Double buffer technique Token bucket + WFQ RAID 5 storage SCAN EDF scheduling RSVP
request Admission control scenario Remote cluster Remote cluster Network connections Disk admission control Local cluster Local distribution network Check available bandwidth
Analysis – admission control • Server disk • , if accept the request • Network overall disk bandwidth client playback rate bandwidth available on jth link reserved rate client playback rate
rJ r1 bJ b1 wJ w1 Analytical model – use delay bound to calculate reserved bandwidth …… : MTU : max packet size for the flow WFQ + Token bucket : retrieval block size
Performance evaluation – request handling policy • Redirect: • A blocked request at one resource is simply redirected to other resources • Split-based • Sharing the loads to other resources
Simulation setup – environment • Servers in local cluster: 5 • Storage capacity per local server: 500 GB • Disk transfer rate at local server: 1.2 Gbps • Hops to remote cluster1: 3 • Hops to remote cluster2: 6 • Max. Transmission Unit: 1500 Bytes • Maximum packet size: 1500 Bytes • Network bandwidth: 2488 Mbps • End-to-end delay 300 ms • Size of video collection 150 • Size of videos in GBytes: 2.46 to 4.8 • Service time in hours: 0.68 to 2.03 • Video popularity: according to Zipf distribution • Request arrival interval: adopt Poisson distribution Remote cluster1 Remote cluster2 Network1 Network2 Local cluster requests
Simulation setup – request handling policies • Redirect • Redirect order: LC RC1 RC2 • Split • Split50-60: 50% are served in LC, 60% of the remains are served in RC1, the rests are in RC2 • Split-redirect • Split first, also contains redirect policy
Simulation setup – scenarios • Replicated video collection (RVC) • All videos are available on local or remote servers • Distributed video collection (DVC) • Only a partial set of videos is available on the local cluster, the requests for non-available parts are served by remote clusters
Simulation results – compare performance of request handling policies in RVC • Purpose: test the performance of the VoD system using different request handling policies • Redirect policy performs better than the other two policies
Split-50-60 performs better at heavy load Split-60-60 performs better at low load Simulation results – difficulties with split-based policies in RVC • The lines are crossed over in the previous figures (Ex: split-50-60 and split-60-60) • It is difficult to pick an efficient split for a given workload
Simulation results – performance at each resources for split policies in RVC • Use individual resource performance to help explain the crossover and divergence behavior
Simulation results – efficient split policy in RVC • Split requests proportional to their resource • It may difficult to know remote clusters since they may be dynamically shared with other user populations
Simulation results – varying the number of videos on local server in DVC • Distribute the available storage capacity at the local cluster to videos in proportion to their popularity • Redirect policy only • Class1: top 20% popular, class2: 20~60% popular, class3: last 40% popular
Conclusion and distribution • Develop a method to analyze distributed VoD systems • Use an extensive simulation to the distributed VoD architecture and evaluate several request handling policies