1. A Peer-to-Peer On-Demand Streaming Service and Its Performance Evaluation Presenter: Nera Liu Author: Yang Guo, Kyoungwon Suh, Jim Kurose and Don Towsley

2. Outline Architecture of Direct Stream Performance Evaluation

4. Data Caching at Clients Each client maintains a moving window of the most recent content that they received. Example: Client buffer = b. Receiving Position = r. Moving Window = [(r-b), r].

5. The Directory Server It maintains information about the content server and clients in order to facilitate the search for candidate parent clients for new requests. Each client is represented by a entry (a, t, r, b) a is the client ’ s IP address t is the time client starts to receive the stream r is the time when the client began at b is the client buffer size

6. Serving a new request The new client sends a request to the directory server to ask for the video starting at position r The directory server looks into its database and returns a list of candidate nodes, including the content server and clients that have the content to serve

7. Serving a new request The new client determines from which node to retrieve the stream using the QoS parent selection algorithm. The new client contacts the selected node and asks for streaming, then the new client signals back to the directory server and registers itself into the database.

8. QoS Parent Selection Algorithm Objective: The minimum bandwidth must equal to playback bitrate The selection of the parent node should allow the DirectStream to serve as many clients as possible in long run

9. QoS Parent Selection Algorithm Assuming the directory server returns a list of candidate to the new client {c i } with n i hop to the new client and available bandwidth of x i The new client uses the distance- bandwidth ratio n i r /x i to select the candidate, where 0 < r < infinity

10. QoS Parent Selection Algorithm The selection of a parent with high available bandwidth helps in balance the workload The selection of short network distance helps in reduce the network traffic => choose the small value of n i r /x i

11. Performance Evaluation Buffer Size E[S] is the server stress to the content server Normalized workload is the Poisson process of client arrival

12. Performance Evaluation 100 nodes Link capacity is in the integer multiple of playback rate Video Length is 100 minutes The value of r in n i r /x i is chosen to be 0.5

13. Performance Evaluation