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Reducing Join Latency in P2P Streaming with Preferred Peer Lists

This method addresses the challenge of join latency in peer-to-peer (P2P) video streaming systems. By implementing a Preferred Peer List (PPL) system, new peers can efficiently connect and receive video streams. The source peer maintains a cache of preferred peers with a high likelihood of availability, enabling quicker joining with reduced latency. Our experimental results demonstrate significant improvements in join time and quality of video streams, highlighting the effectiveness of parent switching and soft handover techniques. This approach leads to a smoother, more responsive viewing experience.

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Reducing Join Latency in P2P Streaming with Preferred Peer Lists

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  1. A Method for P2P Streaming System Join Latency Reduction Using Preferred Peer Lists Jeonghun Noh Sachin Deshpande* Information Systems Laboratory Stanford University * Sharp Laboratories of America

  2. Toward Low Latency P2P Video Streaming • Real-time video streaming is time-sensitive. • Users prefer quick video play-back. • Channel surfing benefits from a short join latency. • Join latency in P2P systems • During join procedure, new peers connect to peers in the system to receive video. • Existing P2P networks: new peers blindly probe for parents at random. GOAL: Design a P2P network that provides a small join latency

  3. Overview • Preferred Peers List System • Overview • Preferred Peer Cache/List • Parent switching • Soft Handover • Experimental Results • Conclusions

  4. Overview: Preferred Peer List System • Preferred Peer Cache (PPC) • Caches information about available peers (preferred peers) in the overlay. • Maintained by the source peer • Preferred peers have a high probability of being available to other peers • Using PPC for peer recommendations • New incoming peers contact the source peer. • The source peer sends a Preferred PeerList (PPL) containing preferred peers. • The new peers directly contact the preferred peersto connect to.

  5. PX PY Partial Learning of the Overlay • Source peer partially learns about the overlay from the peer’s join / leave reports S X Y JOIN Report LEAVE Report

  6. Using the Knowledge about the Overlay • A list of peers, PPL, is created when a recommendation is requested from new peers. • Among the most recently updated peers, peers recommended less often are chosen. Peer address | Use-count | Update time (in secs) PPC (at the source) Selected peers

  7. Video stream … … Join Procedure Using PPL Initial join request • Contact video source • Receive number of trees, video rate • Receive flat list, preferred peer list (PPL) Direct connection and peer probe • Contact preferred peers on PPL • Probe peers on flat list Use probe replies; if preferred peer attempt fails. • Selects best parent from probe replies • Parent selection factor • Available bandwidth • Minimize tree height

  8. Parent Switching • Preferred peer recommendations do not guarantee the best parents • One method to choose better parents • Utilize collected probe replies • Perform the probe-based join process

  9. Distribution Tree at time 71s No Parent Switch : video source : peer in the session : peer that left the session Average Tree Height : 3.76 Average PSNR : 39.71dB

  10. Distribution Tree at time 71s Parent Switch : video source : peer in the session : peer that left the session Average Tree Height : 2.67 Average PSNR : 40.13dB

  11. Soft Handover • Parent switching may cause video discontinuity. • Using Soft Handover • Keep old and new parents simultaneously so that both parents forward video packets. • As soon as duplicate packets are detected, send leave message to old parent.

  12. Experimental Setup • Network simulation in ns-2 • 75 / 300 active peers • Random peer arrival/departure average: ON (90 sec)/OFF (10 sec) • Peer uplink: typical access bandwidth / uniform bandwidth • Video streaming • Mother & Daughter sequence encoded with H.264/AVC @ 281 Kb/s (CIF quality) • 15-minute live multicast • System constructs 4 complimentary multicast trees.

  13. Distribution of Join Latency • Comparison of join time distribution • PPL system versus a probe-based system • Influence of peer uplink bandwidth: heterogeneous / uniform distributions First tree join time Full connection time

  14. Effects of Parent Switching • Simulation setup: 500 secs, uniform bandwidth distribution for peer uplink • PSNR averaged over 10 simulations and 75 peers

  15. Effects of Soft Handover • Observations (+) Up to 55% of redundant packet forwarding is reduced (-) Slight PSNR drop may occur

  16. Conclusions • PPC keeps partial information about the P2P overlay system. • Preferred peers are selected from incomplete PPC. • One step closer to low-latency P2P video streaming: • New peers can join faster. • By switching parent after PPL-based direct attach, overlay quality is improved. • By Soft Handover, up to 55% of redundant video packet transmission can be avoided.

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