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A Method for P2P Streaming System Join Latency Reduction Using Preferred Peer Lists

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. Toward Low Latency P2P Video Streaming. Real-time video streaming is time-sensitive.

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A Method for P2P Streaming System Join Latency Reduction Using 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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