Peer-to-Peer Based Multimedia Distribution Service

1. Peer-to-Peer Based Multimedia Distribution Service Zhe Xiang, Qian Zhang, Wenwu Zhu, Zhensheng Zhang, and Ya-Qin Zhang IEEE TRANSACTIONS ON MULTIMEDIA, April, 2004

2. Outline • Introduction • P2p based multimedia distribution service architecture • Design of the system • Topology-aware overlay • Replication strategies • Simulation results • Conclusion

3. Characteristics of multimedia distribution service in p2p system • A peer shares data with other peers • A peer searches data from other peers • Dedicated server is not needed • Replica is allowed

4. P2p based multimedia distribution service architecture

5. How does a new node join

6. Content Delivery • Node A of group G requests for content C • If C is in group G: transfer directly • If C is not in group G: transfer C to G first • Replication • G may make a replication for delay concern (inter-group replication strategy) • A may make a replication for robust concern (intra-group replication strategy)

7. Inter-group replication strategy • Peer pj in group Gr requests content ci • Find nearest group Gp that contains ci • Calculate avg. distance d between neighbors • If d(Gp,Gr)<d: end • If (free space>size of ci): replicate ci in local storage, end • Else: remove stored contents according to availability (or maybe LRU, LFU,…etc.) • Replicate content ci into local storage

8. Problem formulation • Seed replication matrix X={xij}: • xij=1 if Gj holds seed for content ci • xij=0 otherwise • Access matrix Y={yij} • yij=k: k≠j, d(Gj,Gk)=min{d(Gj,Gs), xis=1} • Inter-group replication: minimize subject to

9. Theoretical analysis • Only consider total capacity: • Avg. distance between neighbors:

10. Popularity factor • Assume popularity follows a Zipf distribution • Suppose M contents are ordered in a descending order of popularity ri: • Normally, skew factor(α) is chosen as 0.271 • The authors vary skew factor from 0.1 to 0.5

11. Intra-group replication strategy • Peer pj requests content cr within its group • Calculate A(cr) • Calculate A’(ci) for any content ci in pj’s storage • Create list {c1,c2…ck} in a descending order of A’(ci) • If (FreeStorage+total size of contents in list)<sr: end • Find j in list such that • Delete contents c1,…cj • Replicate content cr

12. Problem formulation • Replica replication matrix X{xij} • xij=1 if per pj holds a replica of content ci • Xij=0 otherwise • Availability A(ci) of content ci:

13. Simulation methodology • Edge longitude = 300 ms • Group number: 200 • Latency: • Small if in the same group • According to distance if in different group • # of hops increases linearly to distance • Bandwidth ranges from 800 kbps to 1.4 Mbps • 10000 video chips, each is encoded in 1.28 Mbps bit rate • length of video clips: 3~5 min

14. Simulation results

15. Simulation results (cont’)

16. Simulation results (cont’)

17. Simulation results (cont’)

18. Conclusion • Proposed a framework for multimedia distribution based on p2p network • Hosts are self-organized into groups • Proposed heuristic method to make replica in the system