SEMINAR: RECHNERNETZE UND VERTEILTE SYSTEME HS08 Peer-to-Peer Media Streaming Francisco Piña Garrido University Jaen (Spain) November 26th, 2008
Overview > Introduction Definition of Peer to Peer Streaming Components, Services, Current Situation > P2P streaming examples and new implementations An Alliance based Peering Scheme for Peer to Peer Live Media Streaming [1] dhcps: Decentralized Hierarchically Clustered P2P Video Streaming [2] Using Layered Video to Provide Incentives in P2P Live Streaming [3] Understanding Mesh-based Peer to Peer Streaming [4] > Analysis & Preferences > Conclusion & Questions Francisco Piña Garrido, November 26, 2008 2
Introduction > Definition Peer to Peer (or P2P) computer network uses diverse connectivity between participants in a network and the cumulative bandwidth of network participants rather than conventional centralized resources Pure P2P network does not have the notion of clients or servers but only equal peer nodes that simultaneously function as both "clients" and "servers" to the other nodes on the network > Classifications Peer to Peer Networks Used: Content Delivery, File Sharing,Telephony, Media Streaming (audio, video), Discussion Forums Centralization: Peers act as equals, merging the roles of clients and server, no central server, no central router > Examples: Ares, Bittorrent, edonkey, Freenet, Gnutella,... Francisco Piña Garrido, November 26, 2008 3
An Alliance based Peering Scheme for Peer to Peer Live Media Streaming [1] > Main entities: Nodes Media Relaying Server Tracker > Media Server: Origin of stream content for the swarm > Power Nodes: Nodes with higher contribution to the swarm in terms of the content server Nodes with higher uplink capacity Forward the content to the others peers in the swarm Choosing power nodes for direct streaming from Media Server reduces the chances of a bottleneck Prevent wastage of Media Server uplink bandwidth (the most precious resources in the swarm) Francisco Piña Garrido, November 26, 2008 4
An Alliance based Peering Scheme for Peer to Peer Live Media Streaming [1] > Tracker: periodically (10 minutes ) computes the rank of the nodes in terms of the content served to the swarm > The Tracker updates the media server about the new power nodes, which then stream the media content > Alliance Formation Nodes cluster in small groups (4-8), called Alliances, to form symbiotic associations with other peers Members are to be mutually trusted and help each other Each Alliance can have up to h members, and a node can be a part of up to k alliances Parameters (h,k) controlled to form a good conectivity through mutiple paths for receiving the media content Francisco Piña Garrido, November 26, 2008 5
An Alliance based Peering Scheme for Peer to Peer Live Media Streaming [1] > Alliance Formation Node accepts the alliance request: issues a success message Two members of an alliance can expand the alliance futher > Principal architecture and functionality Source: [1] Francisco Piña Garrido, November 26, 2008 6
dhcps: Decentralized Hierarchically Clustered P2P Video Streaming [2] > HCPS Architecture descentralized sheduling method is a able serve a large numbers of users/peers Individual users/peers maintain a small number of peer connections and exchange data with others peer/nodes according to locally available information Capable of accommodating a large number of users and address the system scalability issue faced by P2P Streaming The perfect scheduling employed in HCPS does not work > Types of Peers in the HCPS systems: Source Server: True Server of the entire system Cluster Head: Upper Level and Lower Level Normal Peer: Maintains a playback buffer Francisco Piña Garrido, November 26, 2008 7
dhcps: Decentralized Hierarchically Clustered P2P Video Streaming [2] > Hierarchically Clustered P2P Streaming System Source: [2] Francisco Piña Garrido, November 26, 2008 8
dhcps: Decentralized Hierarchically Clustered P2P Video Streaming [2] > Queue-based P2P system with four nodes Peer a sends pull signal to the content source server Content source server send three chunks in response to the ʻpullʼ signal Three chunks are cached in the forward queue Cached chunks are forwarded to neighbor peers 1) Duplicate chunk is sent to all peers when the server has responded to all ʼpullʼ signals. Source: [2] Francisco Piña Garrido, November 26, 2008 9
Using Layered Video to Provide Incentives in P2P Live Streaming [3] > A heterogeneous system of layered video Video encoded into layers (done by origin server) Lower layers more important Layers further divided into Layer Chunks (LCs) of Δ seconds > Tit-for-tat strategy (like Bittorrent) Peers contributing more uplink bandwith receive more layers Each peer measures its download rates from its neigbours Peers with higher upload contribution likely to be rewarded with more LCs (= more layers = better quality) Francisco Piña Garrido, November 26, 2008 10
Using Layered Video to Provide Incentives in P2P Live Streaming [3] > Supplying peers Receive LC requests from mutiple neighbors Determine which request should be served first Allocate available uplink bandwith to neighbors Upload more to the well providing neighbors (tit-for-tat) Maintain diferent request queues for each receiver Determine which receiver should be served depending on the receiver s contribution to the suplier > Receiving peers Have buffered LCs to be displayed in the future Prioritize requests for missing LCs Determine to which partner peers requests are sent Francisco Piña Garrido, November 26, 2008 11
Using Layered Video to Provide Incentives in P2P Live Streaming [3] > Partner selection Ramdomly select peers from the active peers in the system Locate a partner with the similar uplink bandwidth E.g. choose patner with same ISP or with same type of access Periodically replace the least contributing partner with new peer > Partnership establishment Peers intending to establish partnership exchange buffer maps Peers with higher contribution supposed to receive more layers Uplink bandwidth contribution of peers evaluated on buffer map Francisco Piña Garrido, November 26, 2008 12
Understanding Mesh-Based Peer to Peer Streaming [4] > Overlay Construction Participating peers form randomly connected and directed mesh Connection between pairs is unidirectional Data delivered from a parent to a child peer Each peer (except source) has mutiple parents and children > Advantanges of such an overlay for content delivery Overlay constuction and maintenance are very simple Diverse paths for parents -> children reduces probability of shared bottleneck between these connections Overlay is very resilient to churn Francisco Piña Garrido, November 26, 2008 13
Understanding Mesh-Based Peer to Peer Streaming [4] > Overlay organization Peers organized into levels based on distance to source Level 0 is the source itself Level n>0 consists of all peers n hops away from source > Content delivery among peers Performed using push reporting by parents Coupled with pull requesting by children Requested packets from each parent are determined by a packet sheduling mechanism at child peers > Peers quantify contribution of bandwidth and content bottlettlenecks in delivered quality from each parent. > Available peer bandwidth only depends on overlay properties Francisco Piña Garrido, November 26, 2008 14
Understanding Mesh-Based Peer to Peer Streaming [4] > Mesh-Based P2P Streaming Structure Levels Layers Source: [4] Francisco Piña Garrido, November 26, 2008 15
Analysis > Alliance based Peering Scheme for Peer to Peer Live Media Streaming [1] Robust and scalable behavior Delivers near optimal QoS (varying workloads/conditions) Uplink utilization is improved considerably compared to e.g. CoolStreaming (>90% throughput for large swarms) > dhcps: Descentralized Hierarchically Clustered P2P Video Streaming [2] Capable of providing live streaming service to large number of users with video rates aproaching the maximun streaming rate Francisco Piña Garrido, November 26, 2008 16
Analysis > Using Layered Video to Provide Incentives in P2P Live Streaming [3] More received layers provide better video quality Distributed incetive strategy Peers evaluate their neighbors upload contributions in a distributed manner Uses centralized architectured and enhances scalability > Understanding Mesh-Based Peer to Peer Streaming [4] Live content that incorporates swarm-like delivery Global pattern of content delivery utilizing effectively outgoing bandwidth of participating peers Connectivity in a overlay mesh affects delivered quality to individual peers Francisco Piña Garrido, November 26, 2008 17
Conclusion & Outlook > Alliance based Peering Scheme for Peer to Peer Live Media Streaming [1] Results are promising and could provide research insights towards development of newer and efficient peering strategies > dhcps [2] Can be an excellent solution to provide streaming services over managed networks (ISP controlled IPTV network / cable) > Using Layered Video to Provide Incentives in P2P Live Streaming [3] Can provide incentives for peers to contribute uplink bandwidth > Understanding Mesh-Based Peer to Peer Streaming [4] Presents global pattern of content delivery that is able to effectively utilize outgoing bandwidth of most peers. Francisco Piña Garrido, November 26, 2008 18
References > [1] Purandare, D. and Guha, R. 2007. An alliance based peering scheme for peer-to-peer live media streaming. In Proceedings of the 2007 Workshop on Peer-To-Peer Streaming and IP-TV (Kyoto, Japan, August 27-31, 2007). P2P-TV '07. ACM, New York, NY, 340-345. DOI= http://doi.acm.org/10.1145/1326320.1326328 > [2] Guo, Y., Liang, C., and Liu, Y. 2008. dhcps: decentralized hierarchically clustered p2p video streaming. In Proceedings of the 2008 international Conference on Content-Based Image and Video Retrieval (Niagara Falls, Canada, July 07-09, 2008). CIVR '08. ACM, New York, NY, 655-662. DOI= http://doi.acm.org/10.1145/1386352.1386446 Francisco Piña Garrido, November 26, 2008 19
References > [3] Liu, Z., Shen, Y., Panwar, S. S., Ross, K. W., and Wang, Y. 2007. Using layered video to provide incentives in P2P live streaming. In Proceedings of the 2007 Workshop on Peer-To- Peer Streaming and IP-TV (Kyoto, Japan, August 27-31, 2007). P2P-TV '07. ACM, New York, NY, 311-316. DOI= http://doi.acm.org/10.1145/1326320.1326322 > [4] Magharei, N. and Rejaie, R. 2006. Understanding meshbased peer-to-peer streaming. In Proceedings of the 2006 international Workshop on Network and Operating Systems Support For Digital Audio and Video (Newport, Rhode Island, November 22-23, 2006). NOSSDAV '06. ACM, New York, NY, 1-6. DOI= http://doi.acm.org/10.1145/1378191.1378204 Francisco Piña Garrido, November 26, 2008 20
Questions Francisco Piña Garrido, November 26, 2008 21