On Peer-to-Peer Media Streaming

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. Contents • Introduction • Streaming Model • Media Data Assignment • Admission Control Protocol • Simulation Results • Conclusion

3. Introduction • General P2P System (File) • ‘open-after-downloading’ • P2P Media Streaming System • ‘play-while-downloading’ • Characteristics shared by both categories • Self-growing (capacity amplification) • Server-less (no server-like behavior) • Heterogeneity (bandwidth) (authors omitted storage capacity heterogeneity)

4. Introduction • Characteristic owned by P2P Media Streaming System • Multiple supplying peers

5. Introduction • Two problems addressed • Media data assignment • Fast amplification of streaming capacity • Two solutions proposed • OTSp2p – optimal media data assignment • DACp2p – distributed differentiated admission control protocol

6. Streaming Model • Assumptions: • CBR Video bitrate R0, • Can be partitioned into equal size segments of playback time • Roles of peers: each supplying peers join at most one session at any time • Bandwidth of peers: Out-bound bandwidth of supplying peer Ps: This set of values prevents the assignment problem from becoming the NP-hard binpacking-like problem.

7. Streaming Model • Assumptions: • Classes of peers: N classes according to N values of their out-bound bandwidth, • System capacity: Sum of out-bound bandwidth

8. Optimal Media Data Assignment • Goals: • Continuous playback • Minimum buffering delay at Pr • To determine: • Media segments being transmitted by • Playback start time • Example: • Supplying peers are with out-bound bandwidth of

9. Optimal Media Data Assignment • Different assignments lead to different buffering delay • Assignment 1: buffering delay =

10. Optimal Media Data Assignment • Different assignments lead to different buffering delay • Assignment 2: buffering delay =

11. Optimal Media Data Assignment • Algorithm OTSp2p • m supplying peers sorted in descending order in out-bound bandwidth, • Lowest class among them is class-n • Alogrithm:

12. Optimal Media Data Assignment • Theorem • Given • m supplying peers • OTSp2p will compute an optimal data assignment • Achieves the minimum buffering delay

13. Admission Control Protocol • Requirements: • Should not starve the lower-class peers • Purely distributed fashion • Differentiation – the higher the outbound bandwidth, the greater probability being admitted, with shorter waiting time and buffering delay • DACp2p Characteristics: • Each supplying peer operates individually with requesting peer • Operate in a probabilistic fashion

14. Admission Control Protocol • DACp2p – Supplying Peers • Probabilistic vector • For • For • If being idle for Tout, ‘relaxes’ the admission preference • After serving peer, • If no ‘reminder’ received, ‘relaxes’ the admission preference • If certain ‘reminder’ received before, ‘tightens’ the admission preference

15. Admission Control Protocol • DACp2p – Requesting Peers • Randomly select M supplying peers via some peer-to-peer lookup mechanism • Pr will be admitted • if obtains enough permissions among the M peers such that • they are neither down nor busy • willing to provide the service • their aggregated out-bound bandwidth is enough • then execute OTSp2p to compute the data assignment

16. Admission Control Protocol • DACp2p – Requesting Peers • Pr will be rejected • not enough permissions from these M peers • leaves a ‘reminder’ to a subset W • W is chosen from busy peers as follows: • currently favors the class of Pr • the aggregated out-bound bandwidth offered by W is equal to • Backoff for at least a period of Tbkf before another request • xth rejection, backoff period = Note that the rejected peer may not in the future being served by the exactly the same set of W.

17. Simulation Results • Performance Metrics: • System capacity amplification • Request admission rate • Average buffering delay • Average waiting time (before admission)

18. Simulation Results • Simulation Environment • Total 50,100 peers (50,000 requesting + 100 ‘seed’) • Video length = 60mins • Supplying peer are class-1 peer • Requesting peers: class(1, 2, 3, 4) = (0.1, 0.1, 0.4, 0.4) • M = 8, probes 8 randomly selected supplying peers • Tout = 20mins, Tbkf = 10mins, Ebkf = 2 • Simulation time = 144 hrs, first request in first 72 hrs • Comparison situation of non-differentiated admission control protocol (NDACp2p):

19. Simulation Results • System Capacity Amplification

20. Simulation Results • Request Admission Rate

21. Simulation Results • Average buffering delay

22. Simulation Results • Average Waiting Time • Given average number of rejections x, average waiting time can be computed as

23. Conclusion • Problems in Peer-to-Peer Media Streaming • Media data assignment • Fast capacity amplification • Solutions Proposed • Algorithm OTSp2p • Distributed DACp2p protocol • DACp2p Features • Fast system capacity amplification • Benefits all requesting peers in • admission rate • waiting time • buffering delay • Create an incentive of peers to offer truly available out-bound bandwidth

24. End of Presentation Thank you!