On Peer-to-Peer Media Streaming by Dongyan Xu, Mohamed Hefeeda, Susanne Hambrusch, Bharat Bhargava Dept. of Computer Science, Purdue University, West Lafayette

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

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)

Introduction Characteristic owned by P2P Media Streaming System Multiple supplying peers

Introduction Two problems addressed Media data assignment Fast amplification of streaming capacity Two solutions proposed OTS p2p – optimal media data assignment DAC p2p – distributed differentiated admission control protocol

Streaming Model Assumptions: CBR Video bitrate R 0, 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 P s : This set of values prevents the assignment problem from becoming the NP-hard binpacking-like problem.

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

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

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

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

Optimal Media Data Assignment Algorithm OTS p2p m supplying peers sorted in descending order in out- bound bandwidth, Lowest class among them is class-n Alogrithm:

Optimal Media Data Assignment Theorem Given m supplying peers OTS p2p will compute an optimal data assignment Achieves the minimum buffering delay

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 DAC p2p Characteristics: Each supplying peer operates individually with requesting peer Operate in a probabilistic fashion

Admission Control Protocol DAC p2p – Supplying Peers Probabilistic vector For If being idle for T out, ‘relaxes’ the admission preference After serving peer, If no ‘reminder’ received, ‘relaxes’ the admission preference If certain ‘reminder’ received before, ‘tightens’ the admission preference

Admission Control Protocol DAC p2p – Requesting Peers Randomly select M supplying peers via some peer- to-peer lookup mechanism P r 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 OTS p2p to compute the data assignment

Admission Control Protocol DAC p2p – Requesting Peers P r 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 P r the aggregated out-bound bandwidth offered by W is equal to Backoff for at least a period of T bkf 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.

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

Simulation Results Simulation Environment Total 50,100 peers (50,000 requesting ‘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 T out = 20mins, T bkf = 10mins, E bkf = 2 Simulation time = 144 hrs, first request in first 72 hrs Comparison situation of non-differentiated admission control protocol (NDAC p2p ):

Simulation Results System Capacity Amplification

Simulation Results Request Admission Rate

Simulation Results Average buffering delay

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

Conclusion Problems in Peer-to-Peer Media Streaming Media data assignment Fast capacity amplification Solutions Proposed Algorithm OTS p2p Distributed DAC p2p protocol DAC p2p 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

End of Presentation Thank you!