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Live Sky

Live Sky . Enhancing CDN with P2P HAO YIN XUENING LIU TONGYU ZHAN VYAS SEKAR FENG QIU CHUANG LIN HUI ZHANG BO LI. INTRODUCTION. A commercial hybrid CDN-P2P live streaming system which inherits the best of both CDN and P2P technologies

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Live Sky

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  1. Live Sky Enhancing CDN with P2P HAO YIN XUENING LIU TONGYU ZHAN VYAS SEKAR FENG QIU CHUANG LIN HUI ZHANG BO LI

  2. INTRODUCTION • A commercial hybrid CDN-P2P live streaming system which inherits the best of both CDN and P2P technologies • Content Delivery Networks (CDNs) and Peer-to-Peer (P2P) systems are two alternative and competing technologies for delivering Internet live streaming.

  3. CONTENT DELIVERY NETWORKS • Deploy servers in multiple geographically areas • Uses Client-Server approach • Excellent quality within the Bandwidth limits. • Low Scalability

  4. PEER TO PEER NETWORKS • Each node acts as both client and server • Low server Requirements • High Scalability • Video quality is not guaranteed

  5. CDN vs. P2P CDN P2P

  6. Key Challenges • 1) Ease of integration with existing CDN infrastructure. • 2) Dynamic resource scaling while guaranteeing quality-of-service. • 3) Providing good user experience, ensuring network friendliness and upload fairness.

  7. ARCHITECTURE • MANAGEMENT CENTER • CACHE SERVERS(Service Nodes) • END HOSTS

  8. System Operation • Step1:Client obtains the url of the content source • Step2:GSLB component determines the client location and edge SN location redirects request to suitable SN • Step3:Edge SN serves as • a regular server for legacy clients • a tracker for the p2p operation • a seed for the p2p operation • Step4:edge SN will determine whether to server the client in CDN-mode or P2p- mode

  9. Client Side Content Distribution • Two types of clients: 1)Legacy clients • Receive content directly from edge SN’s 2)Live sky–enabled • receive content either from edge SN’s or from p2p mechanisms • needs to install Live Sky client software to use p2p resources

  10. P2P MECHANISM • Two Types 1)Tree Based • Provides low source-to-end delay • Fails to effectively use the upload capacity of peers 2)Mesh Based • Effectively uses the upload capacity of peers • Delay in the delivery of video content • Typically use large buffers

  11. ADAPTATION • Key challenge is to adapt CDN-P2P operation with good performance and low operating costs of CDN • Important parameters in working environment of hybrid CDN-P2P system • The media play back rate • Total number of end users • Bandwidth capacity of end users • Delay between video source and end user • Upload bandwidth capacity of end users

  12. OPTIMIZATIONS • Fast startup • Minimize the client buffer size to 15 seconds • Live sky leverages the edge SN’s to provide fast startup • Stability under churn • Peers who suffer performance degradation due to churn can retrieve data directly from edge SN • Transmission locality • Clients mostly peer with other clients in the same region • NAT handling • Adopt techniques such as STUN which uses UDP for efficient transmission between clients behind NAT’s

  13. DEPLOYMENT • Live Sky was deployed in china on Oct 22,2007 • In this event 400 kbps video stream was provided and peek number of clients was more than 145,000. • 34 Gbps of bandwidth contribution from CDN servers • 17 Gbps of bandwidth contribution from P2P technologies • Live Sky successfully saved 40% of CDN bandwidth cost by integrating P2P technologies

  14. USER EXPERIENCE • We evaluate the user experience by several factors • Rebuffering Rate: number of clients that rebuffered for playback per minute • Join and Leave rate: number of clients that join the system and leave the system • We correlate the rebuffering rate with the join and leave rate • Join rate is the dominant factor affecting rebuffering rate

  15. DELAY COMPARISONS • Startup delay is the crucial factor in user quality • In Live Sky more than 85% of the clients wait less than 15 s for play back to commence from clicking on link • Source-to-end delay is another crucial factor in user quality • It is defined as the latency a video segment has been sent out from the server until it is viewed on client side • In Live Sky more than 85% of clients experience less than 30s source-to-end delay

  16. NETWORK FRIENDLINESS • We evaluate the locality of the P2P transmissions by analyzing the DNS-based redirections used by the CDN • Two potential sources of errors • Clients may have misconfigured their local DNS server • The IP to location mapping might be out of date • Most P2P traffic in LiveSky is localized within the region and this ensures “network-friendly” operation

  17. ENHANCEMENTS • P2P Group Handling: • We enable the peers to communicate with other clients assigned to different edge SN’s • We only enable the edge SN’s in the same district to exchange client information • NAT Traversing: • We leverage the edge SN to serve as an intermediary to facilitate all the NAT traversal • To reduce the stress on edge SN,we leverage the client as an intermediary to facilitate NAT traversing for other peers

  18. FUTURE WORK • Improving P2P technologies for live streaming • Using scaling option of video coding for fast startup • Efficient allocation of resources between multiple application and channels supported by LiveSky • Better security features

  19. CONCLUSION • LiveSky use existing P2P technologies and integrate them with minimal changes to existing CDN • LiveSky scales with the number of users, at the same time provide the user with good viewer experience • LiveSky system can make a good trade-off among the properties of scalability,Qos,guarantee,availability.

  20. QUESTIONS

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