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 p j in group G r requests content c i  Find nearest group G p that contains c i  Calculate avg. distance d between neighbors  If d(G p,G r )<d: end  If (free space>size of c i ): replicate c i in local storage, end  Else: remove stored contents according to availability (or maybe LRU, LFU,…etc.)  Replicate content c i into local storage

8. Problem formulation  Seed replication matrix X={x ij }:  x ij =1 if Gj holds seed for content c i  x ij =0 otherwise  Access matrix Y={y ij }  y ij =k: k≠j, d(G j,G k )=min{d(G j,G s ), x is =1}  Inter-group replication: subject to minimize

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 r i :  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 p j requests content c r within its group  Calculate A(c r )  Calculate A’(c i ) for any content c i in p j ’s storage  Create list {c 1,c 2 …c k } in a descending order of A’(c i )  If (FreeStorage+total size of contents in list)<s r: end  Find j in list such that  Delete contents c 1,…c j  Replicate content c r

12. Problem formulation  Replica replication matrix X{x ij }  x ij =1 if per p j holds a replica of content c i  X ij =0 otherwise  Availability A(c i ) of content c i :

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’)

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