1. Scalable and Continuous Media Streaming on Peer-to-Peer Networks M. Sasabe, N. Wakamiya, M. Murata, H. Miyahara Osaka University, Japan Presented By Tsz Kin Ho 13/10/2003

2. Agenda Background System architecture Movie segmentation Block-search algorithm Block-retrieval algorithm Simulation results Conclusion and discussion

3. Background Client-server streaming Lacks scalability and stability Proxy mechanism cannot adapt to Variations of user locations Diverse user demands Peer-to-peer streaming Inherent scalability New network paradigm to solve these problems

4. Background Application-level multicast tree Most of the p2p streaming research works focusing Effective for live streaming, not for on-demand media streaming Single point of failure at root Focus on providing scalable and effective on-demand media streaming on pure P2P networks

5. Architecture

6. Main Goals Bandwidth & storage efficiency Segmentation of stream into “ block ” Scalability Scalable block-search algorithm Reduce amount of query message Continuity Block-retrieval algorithm Determine set of peers as provider Achieve continuous media playback

7. Segmentation of movie Movies are segmented into small process unit “ block ” A block can be encoded and decoded by itself, e.g. the GoP in MPEG2 Each peer maintains a part or the whole of some movies that it has watched or is watching

8. Segmentation of media stream Smaller block More search message Difficult to maintain cache buffer Longer block Fewer search message Drastic changes in network condition while retrieving a block Block size affects system scalability Block size of 10 sec in experiment

9. Block-search algorithm Per-group search Periodically sends out a query message for N consecutive blocks (Round-based)

10. Block-search algorithm Consumer peer Waits for a response for first block Aborts watching if no response arrives after 4 seconds (based on the 8-second rule) Retrieve first block immediately Estimates the available bandwidth and delay from the provider peer Schedule other blocks using the delay and playback deadline

11. Block-search algorithm F ull flooding Flooding with fixed TTL L imited Flooding Flooding with decreased TTL based on the search result on previous round S elective search Temporal order of reference in media stream Expect replied provider peers will contain some blocks in next round Directly send queries to known peers to confirm the existence of desired blocks

12. Block-search algorithm Conjectured contents of cache buffers of peers : R FL method If R contains all next round blocks => Limited flooding otherwise => Full flooding FLS method If R contains all next round blocks => Selective search If R contains some next round blocks => Limited flooding Otherwise => Full Flooding

13. Block-retrieval algorithm More than one peer may contain the required blocks When receiving a response message, consumer determine optimum set of provider by Choosing set of providers that can send out block in time Choosing under Select Fastest (SF) method Select Reliable (SR) method

14. Block-retrieval algorithm Select Fastest (SF) method select a peer whose estimated retrieval time is the smallest among peers Select Reliable (SR) method select a peer with the lowest possibility of block disappearance in cached buffer among peers

15. Simulation Result Movie bit rate = CBR 500 kbps Random network with 100 peers Generated by Waxman algorithm RTT between two contiguous peers ranges from 10ms to 660ms Available bandwidth randomly generated and fixed between 500 and 600 kbps

16. Simulation Result 40 movie of 60 minutes, which are Zipf distributed with = 1.0 Average peer idle time is exponentially distributed with mean = 20 minutes Cache buffer LRU replacement size 675 MB (about size of 3 movie) 6 blocks in a round Block size of 10 sec

17. Simulation Result Metric Scalability Average number of queries that a peer receives during the simulation Continuity Completeness = (number of block in time / number of block of movie)

18. Simulation Result Scalability

19. Simulation Result Continuity Completeness with 95% CI About 70% of total request are complete Popularity

20. Conclusion Proposed scalable block-search and block-retrieval method in p2p media streaming FLS method can provide users with continuous media playback Future works Determination of block size Effective cache replacement algorithm Dynamic network

21. Discussion Quite related to SLVoD project Simulation model not realistic Network model Total Storage requirement is 300 movie space (with only 40 movies) FLS is very effective for LRU cache replacement Only 70% completeness Bandwidth is not dedicated after the search, more than one client may schedule the transmission at the same time

22. References M. Sasabe, N. Wakamiya, M. Murata, H. Miyahara, “ Scalable and Continuous Media Streaming on Peer-to-Peer Networks ”, proc. P2P 2003 M. Sasabe, Presentation Slides at P2P 2003