PRIME: Peer-to-Peer Receiver-Driven Mesh-Based Streaming

1. PRIME: Peer-to-Peer Receiver-Driven Mesh-Based Streaming Nazanin Magharei Reza Rejaie Represented by: Pavneet Singh Min Luo

2. Contents of Presentation • Introduction to PRIME • Overlay construction in PRIME • Content Delivery in PRIME • Performance Evaluation of PRIME • Conclusions

3. Introduction to PRIME

4. Introduction to PRIME PRIME, a scalable mesh-based P2P streaming mechanism for live content, is based on the concept of P2P.

5. Introduction to PRIME • A peer-to-peer, commonly abbreviated to P2P, is a distributed network architecture. It composes of participants that make a portion of their resources directly available to other network participants, without the need for central coordination instances.

6. Introduction to PRIME This is a diagram of a server-based computer network.

7. Introduction to PRIME This is a diagram of a Peer-to-Peer computer network.

8. Introduction to PRIME • Recently, the success of file swarming mechanisms (e.g., BitTorrent) has motivated another approach to P2P streaming that we call mesh-based P2P streaming. • Swarmstreaming is a technology designed to provide lightning-fast downloads of web content and multimedia without any special server software or special plugins/files. Peers form a mesh-shaped overlay and incorporate swarming (or pull) content delivery.

9. Introduction to PRIME

10. Introduction to PRIME Here is a mesh-based P2P streaming mechanism called SplitStream.

11. Introduction to PRIME • However, all those mechanisms cannot deliver live content efficiently. Ⅰ Ensuring the in-time delivery for individual packets of streaming content is difficult. Ⅱ Since the content is progressively generated by a live source, the availability of new content for delivery is limited.

12. Introduction to PRIME • So, the PRIME was designed, which is a new mesh-based P2P streaming mechanism for delivery of live content. The overlay of PRIME

13. Introduction to PRIME • The delivery pattern contains two phases: • Diffusion phase: Data rapidly flows away from source; • Swarming phase: Where peers exchange their available packets.

14. Introduction to PRIME

15. Introduction to PRIME • As the authors follow a performance-driven approach to design PRIME, in order to measure such performance, two bottlenecks are identified here: (i) Bandwidth bottleneck: content delivery from its neighbors not fully utilize its incoming access link bandwidth. (ii) Content bottleneck: there’s not sufficient amount of useful content among its neighbors to effectively utilize its available bandwidth from them.

16. Overlay construction in PRIME

17. Overlay construction in PRIME • Participating peers in PRIME maintain a randomly connected and directed overlay. • There is a parent-child relationship between connected peers and content is always delivered from the parent the child. • Each peer maintains connections from multiple parent and serves multiple children. All connections are initiated by children.

18. Overlay construction in PRIME • To construct the overlay, each peer tries to maintain a sufficient number of parents that can collectively fill its incoming access link bandwidth. • Here, the author roughly estimated the average bandwidth for a connection between parent p to child c as • MIN( )

19. Overlay construction in PRIME • MIN( ) Outgoing bandwidth Outgoing degree of peer p Incoming bandwidth Incoming degree of peer c

20. Overlay construction in PRIME • So to avoid a significant bottleneck, we have the bandwidth-degree condition bwpf infers as bandwidth, or bandwidth-per-flow. This condition implies that all connections in the overlay have roughly the same bandwidth, and this will minimize the bottleneck. This is the first main finding in this paper.

21. Content delivery in PRIME

22. Content delivery in PRIME • PRIME incorporates swarming content delivery which combines push content reporting by parents, with pull content requesting by children. • Each peer, as a parent, progressively reports the availability of its new packets to all of its children.

23. Content delivery in PRIME • In the context of live P2P streaming applications, source progressively generates a new segment of content once every △ seconds. Such segment consists of a group of packets. • So the peer should maintain ω* △ seconds of playout time to swarm among peers.

24. Content delivery in PRIME • This playout delay between the source and peers has two implications: • Each peer should buffer at least ω* △ seconds worth of content • Each packet should be delivered within ω* △ seconds from its generation time to ensure in-time delivery.

25. Content delivery in PRIME • For the delivery of a single segment, the diffusion phase should first considered. • Peers in level 1 can pull all data units from source during the next interval △ after the new segment is available. It will take depth * △ seconds until at least one data unit reaches each peer in the system.

26. Content delivery in PRIME Diffusion time Diffusion connections Diffusion parents Diffusion sub-tree

27. Content delivery in PRIME Swarming connections Swarming parents Pull missing data units from parents in same or lower levels in different sub-tree

28. Content delivery in PRIME • For a given overlay, the minimum number of swarming intervals (Kmin) is determined such that a majority of peers can receive their required number of data units of a segment. • As we mentioned that the required buffer contains ω* △ seconds content, we should have (depth+ Kmin)≤ ω

29. Content delivery in PRIME The relevant packets at each scheduling event is divided into 3 sub-windows: • Playing Sub-window • Swarming Sub-window • Diffusion Sub-window

30. Content delivery in PRIME The packet scheduling scheme at each peer is invoked once every △ seconds and takes the following steps: • Quality Adaptation • Requesting Diffusion Packets • Requesting Playing Packets • Requesting Swarming Packets

31. Content delivery in PRIME • Requesting Swarming Packets • Selecting Timestamp • Assigning Packets (1)Description Selection (Random or rarest description from the useful descriptions among parents) (2)Parent Selection (Random or based on the minimum ratio of its assigned packets to its total packet budget)

32. Content delivery in PRIME • Source can minimize the potential overlap among the delivered content to different diffusion sub-trees and maximize the diffusion rate (the rate of delivery for new packets from source to peers in level 1).

33. Performance Evaluation of PRIME

34. Performance Evaluation of PRIME • X axis = Degree, Y axis = % of pop. With quality better than 90% • Degree < 6 : Population is low because of content bottleneck • Degree > 15: Low because of increase in loss rate of individual connections. Peer Connectivity

35. Performance Evaluation of PRIME

36. Performance Evaluation of PRIME • X Axis: Percentage of content bottleneck, Y axis: Percentage of population. • Up to degree 12, content bottleneck increases with a moderate rate with increase in degree due to improved diversity. • Beyond degree 12, increase in content bottleneck due to increase in loss rate is much higher. • Reason: Increase in loss rate.

37. Performance Evaluation of PRIME • This is the second main finding in this paper. • There is a sweet range for peer degree over which swarming content delivery exhibits a good performance and effectively scales with peer population. • The lower bound of this range is 6 but the upper bound is determined by peer bandwidth.

38. Performance Evaluation of PRIME Loss Rate X Axis: Degree Y Axis: Bandwidth

39. Performance Evaluation of PRIME • First gap shows bandwidth associated with lost packets at outgoing access links. • Second gap shows bandwidth associated with lost packets at incoming access links. • Aggregate throughput from parent peer to all of its children's decreases with increase in peer degree.

40. Performance Evaluation of PRIME Buffer Requirement X Axis: Degree Y Axis: Kmin

41. Performance Evaluation of PRIME • Kmin = Required Swarming intervals • As degree increases from 3 to 15, Kmin first decreases because of improved diversity and then becomes constant. • For degree> 15, Kmin increases due to content bottleneck and loss rate of individual connections.

42. Performance Evaluation of PRIME • The average path length of individual peers decreases with increase in peer degree due to increase in overlay depth. Pattern of Content Delivery

43. Performance Evaluation of PRIME Bi- vs. Uni- Directional Connectivity • For peer degree 4, difference of 1 hop count. • As degree increases, difference in hop count decreases. X Axis: Average hop count Y Axis: Perc. Of Pop. With 90% of desirable data.

44. Performance Evaluation of PRIME • This is the third main finding in this paper. • The minimum buffer requirement at each peer is directly proportional to the total duration of the diffusion and swarming phases for each packet. • Bi-directional overlays require larger buffering than Uni-directional overlays.

45. Performance Evaluation of PRIME Bandwidth Heterogeneity X axis: Perc. Of content bottleneck Y axis: Perc. Of Pop. With 90% of desirable data.

46. Performance Evaluation of PRIME • How is delivery quality affected due to presence of low bandwidth peers. • Minor increase in content bottleneck as the percentage of parents with high bandwidth decreases. • Content bottleneck also depends upon the position of high bandwidth peers.

47. Performance Evaluation of PRIME • This is the fourth main finding in this paper. • When the amount of resources is sufficient, the heterogeneity and asymmetry of access link bandwidth cannot significantly affects the delivered quality to individual peers.

48. Performance Evaluation of PRIME Packet Scheduling

49. Performance Evaluation of PRIME • This graph uses different packet scheduling algo. • The graph suggests that neither criteria for selecting the description of a packet nor the relative order of selection affects performance. • Scheduling in which packet is requested from a random parent is more likely to experience content bottleneck.

50. Performance Evaluation of PRIME • This is the fifth main finding in this paper. • When load is properly balanced among parents, the performance of delivery has not significantly influenced.