On Peer-to-Peer Media Streaming


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On Peer-to-Peer Media Streaming

  1. 1. On Peer-to-Peer Media Streaming by Dongyan Xu, Mohamed Hefeeda, Susanne Hambrusch, Bharat Bhargava Dept. of Computer Science, Purdue University, West Lafayette
  2. 2. Contents <ul><li>Introduction </li></ul><ul><li>Streaming Model </li></ul><ul><li>Media Data Assignment </li></ul><ul><li>Admission Control Protocol </li></ul><ul><li>Simulation Results </li></ul><ul><li>Conclusion </li></ul>
  3. 3. Introduction <ul><li>General P2P System (File) </li></ul><ul><ul><li>‘ open-after-downloading’ </li></ul></ul><ul><li>P2P Media Streaming System </li></ul><ul><ul><li>‘ play-while-downloading’ </li></ul></ul><ul><li>Characteristics shared by both categories </li></ul><ul><ul><li>Self-growing (capacity amplification) </li></ul></ul><ul><ul><li>Server-less (no server-like behavior) </li></ul></ul><ul><ul><li>Heterogeneity (bandwidth) (authors omitted storage capacity heterogeneity) </li></ul></ul>
  4. 4. Introduction <ul><li>Characteristic owned by P2P Media Streaming System </li></ul><ul><ul><li>Multiple supplying peers </li></ul></ul>
  5. 5. Introduction <ul><li>Two problems addressed </li></ul><ul><ul><li>Media data assignment </li></ul></ul><ul><ul><li>Fast amplification of streaming capacity </li></ul></ul><ul><li>Two solutions proposed </li></ul><ul><ul><li>OTS p2p – optimal media data assignment </li></ul></ul><ul><ul><li>DAC p2p – distributed differentiated admission control protocol </li></ul></ul>
  6. 6. Streaming Model <ul><li>Assumptions: </li></ul><ul><ul><li>CBR Video bitrate R 0 , </li></ul></ul><ul><ul><li>Can be partitioned into equal size segments of playback time </li></ul></ul><ul><ul><li>Roles of peers: each supplying peers join at most one session at any time </li></ul></ul><ul><ul><li>Bandwidth of peers: Out-bound bandwidth of supplying peer P s : </li></ul></ul>This set of values prevents the assignment problem from becoming the NP-hard binpacking-like problem.
  7. 7. Streaming Model <ul><li>Assumptions: </li></ul><ul><ul><li>Classes of peers: N classes according to N values of their out-bound bandwidth, </li></ul></ul><ul><ul><li>System capacity: Sum of out-bound bandwidth </li></ul></ul>
  8. 8. Optimal Media Data Assignment <ul><li>Goals: </li></ul><ul><ul><li>Continuous playback </li></ul></ul><ul><ul><li>Minimum buffering delay at P r </li></ul></ul><ul><li>To determine: </li></ul><ul><ul><li>Media segments being transmitted by </li></ul></ul><ul><ul><li>Playback start time </li></ul></ul><ul><li>Example: </li></ul><ul><ul><li>Supplying peers are with out-bound bandwidth of </li></ul></ul>
  9. 9. Optimal Media Data Assignment <ul><li>Different assignments lead to different buffering delay </li></ul><ul><ul><li>Assignment 1: buffering delay = </li></ul></ul>
  10. 10. Optimal Media Data Assignment <ul><li>Different assignments lead to different buffering delay </li></ul><ul><ul><li>Assignment 2: buffering delay = </li></ul></ul>
  11. 11. Optimal Media Data Assignment <ul><li>Algorithm OTS p2p </li></ul><ul><ul><li>m supplying peers sorted in descending order in out-bound bandwidth, </li></ul></ul><ul><ul><li>Lowest class among them is class- n </li></ul></ul><ul><ul><li>Alogrithm: </li></ul></ul>
  12. 12. Optimal Media Data Assignment <ul><li>Theorem </li></ul><ul><ul><li>Given </li></ul></ul><ul><ul><ul><li>m supplying peers </li></ul></ul></ul><ul><ul><li>OTS p2p will compute an optimal data assignment </li></ul></ul><ul><ul><ul><li>Achieves the minimum buffering delay </li></ul></ul></ul>
  13. 13. Admission Control Protocol <ul><li>Requirements: </li></ul><ul><ul><li>Should not starve the lower-class peers </li></ul></ul><ul><ul><li>Purely distributed fashion </li></ul></ul><ul><ul><li>Differentiation – the higher the outbound bandwidth, the greater probability being admitted, with shorter waiting time and buffering delay </li></ul></ul><ul><li>DAC p2p Characteristics: </li></ul><ul><ul><li>Each supplying peer operates individually with requesting peer </li></ul></ul><ul><ul><li>Operate in a probabilistic fashion </li></ul></ul>
  14. 14. Admission Control Protocol <ul><li>DAC p2p – Supplying Peers </li></ul><ul><ul><li>Probabilistic vector </li></ul></ul><ul><ul><ul><li>For </li></ul></ul></ul><ul><ul><ul><li>For </li></ul></ul></ul><ul><ul><li>If being idle for T out , ‘relaxes’ the admission preference </li></ul></ul><ul><ul><li>After serving peer, </li></ul></ul><ul><ul><ul><li>If no ‘reminder’ received, ‘relaxes’ the admission preference </li></ul></ul></ul><ul><ul><ul><li>If certain ‘reminder’ received before, ‘tightens’ the admission preference </li></ul></ul></ul>
  15. 15. Admission Control Protocol <ul><li>DAC p2p – Requesting Peers </li></ul><ul><ul><li>Randomly select M supplying peers via some peer-to-peer lookup mechanism </li></ul></ul><ul><ul><li>P r will be admitted </li></ul></ul><ul><ul><ul><li>if obtains enough permissions among the M peers such that </li></ul></ul></ul><ul><ul><ul><ul><li>they are neither down nor busy </li></ul></ul></ul></ul><ul><ul><ul><ul><li>willing to provide the service </li></ul></ul></ul></ul><ul><ul><ul><ul><li>their aggregated out-bound bandwidth is enough </li></ul></ul></ul></ul><ul><ul><ul><li>then execute OTS p2p to compute the data assignment </li></ul></ul></ul>
  16. 16. Admission Control Protocol <ul><li>DAC p2p – Requesting Peers </li></ul><ul><ul><li>P r will be rejected </li></ul></ul><ul><ul><ul><li>not enough permissions from these M peers </li></ul></ul></ul><ul><ul><ul><li>leaves a ‘reminder’ to a subset W </li></ul></ul></ul><ul><ul><ul><li>W is chosen from busy peers as follows: </li></ul></ul></ul><ul><ul><ul><ul><li>currently favors the class of P r </li></ul></ul></ul></ul><ul><ul><ul><ul><li>the aggregated out-bound bandwidth offered by W is equal to </li></ul></ul></ul></ul><ul><ul><ul><li>Backoff for at least a period of T bkf before another request </li></ul></ul></ul><ul><ul><ul><li>x th rejection, backoff period = </li></ul></ul></ul>Note that the rejected peer may not in the future being served by the exactly the same set of W .
  17. 17. Simulation Results <ul><li>Performance Metrics: </li></ul><ul><ul><li>System capacity amplification </li></ul></ul><ul><ul><li>Request admission rate </li></ul></ul><ul><ul><li>Average buffering delay </li></ul></ul><ul><ul><li>Average waiting time (before admission) </li></ul></ul>
  18. 18. Simulation Results <ul><li>Simulation Environment </li></ul><ul><ul><li>Total 50,100 peers (50,000 requesting + 100 ‘seed’) </li></ul></ul><ul><ul><li>Video length = 60mins </li></ul></ul><ul><ul><li>Supplying peer are class-1 peer </li></ul></ul><ul><ul><li>Requesting peers: class(1, 2, 3, 4) = (0.1, 0.1, 0.4, 0.4) </li></ul></ul><ul><ul><li>M = 8, probes 8 randomly selected supplying peers </li></ul></ul><ul><ul><li>T out = 20mins, T bkf = 10mins, E bkf = 2 </li></ul></ul><ul><ul><li>Simulation time = 144 hrs, first request in first 72 hrs </li></ul></ul><ul><ul><li>Comparison situation of non-differentiated admission control protocol (NDAC p2p ): </li></ul></ul>
  19. 19. Simulation Results <ul><li>System Capacity Amplification </li></ul>
  20. 20. Simulation Results <ul><li>Request Admission Rate </li></ul>
  21. 21. Simulation Results <ul><li>Average buffering delay </li></ul>
  22. 22. Simulation Results <ul><li>Average Waiting Time </li></ul><ul><ul><li>Given average number of rejections x , average waiting time can be computed as </li></ul></ul>
  23. 23. Conclusion <ul><li>Problems in Peer-to-Peer Media Streaming </li></ul><ul><ul><li>Media data assignment </li></ul></ul><ul><ul><li>Fast capacity amplification </li></ul></ul><ul><li>Solutions Proposed </li></ul><ul><ul><li>Algorithm OTS p2p </li></ul></ul><ul><ul><li>Distributed DAC p2p protocol </li></ul></ul><ul><li>DAC p2p Features </li></ul><ul><ul><li>Fast system capacity amplification </li></ul></ul><ul><ul><li>Benefits all requesting peers in </li></ul></ul><ul><ul><ul><li>admission rate </li></ul></ul></ul><ul><ul><ul><li>waiting time </li></ul></ul></ul><ul><ul><ul><li>buffering delay </li></ul></ul></ul><ul><ul><li>Create an incentive of peers to offer truly available out-bound bandwidth </li></ul></ul>
  24. 24. End of Presentation Thank you!