P2P Streaming - Part-1: Native Multicast,

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Transcript of P2P Streaming - Part-1: Native Multicast,

  • 1. P2P Streaming - Part-1: Native Multicast,End-System Multicast,and intro to P2P-Streaming CS 7270 Networked Applications & Services Lecture-12

2. Reading-1

  • Opportunities and Challenges of Peer-to-Peer Internet Video Broadcast by J. Liu et al.
  • Very nicely written tutorial
  • To appear at IEEE Proceedings this year
  • Based on (highly influential) ESM project from Hui Zhangs group at CMU
  • Huis slides:http:// www.cs.cmu.edu/~hzhang/Talks/ESMPrinceton.pdf

3. Reading-2

  • Insights into PPLive: A Measurement Study of a LargeScale P2P IPTV System by X. Hei et al.
  • PPLive: one of the most popular P2Pstreaming systems, mostly used for Chinese TV shows
  • Very little known about system architecture
  • The paper attempts a measurement-based reverse engineering study

4. Basics

  • PPLive: free P2P-based IPTV
  • As of January 2006, the PPLive network provided 200+ channels with 400,000 daily users on average.
  • The bit rates of video programs mainly range from 250 Kbps to 400 Kbps with a few channels as high as 800 Kbps.
  • The video content is mostly feeds from TV channels in Mandarin.
  • The channels are encoded in two video formats: Window Media Video (WMV) or Real Video (RMVB).
  • The encoded video content is divided into chunks and distributed to users through the PPLive P2P network.

5. System architecture 6.

  • Cached contents can be uploaded to other peers watching the same channel.
  • This peer may also upload cached video chunks to multiple peers.
  • Received video chunks are reassembled in order and buffered in queue of PPLive TV engine, forming local streaming file in memory.
  • When the streaming file length crosses a predefined threshold, the PPLive TV engine launches media player, which downloads video content from local HTTP streaming server.
  • After the buffer of the media player fills up to required level, the actual video playback starts.
  • When PPLive starts, the PPLive TV engine downloads media content from peers aggressively to minimize playback start-up delay.
  • When the media player receives enough content and starts to play the media, streaming process gradually stabilizes.
  • The PPLive TV engine streams data to the media player at media playback rate.

7. Measurement setup

  • One residential and one campus PC watched channel CCTV3
  • The other residential and campus PC watched channel CCTV10
  • Each of these four traces lasted about 2 hours.
  • From the PPLive web site, CCTV3 is a popular channel with a 5-star popularity grade and CCTV10 is less popular with a 3-star popularity grade.

8. Session durations

  • Signaling versus video sessions
  • All sessions are TCP based
  • The median video session is about 20 seconds and about 10% of video sessions last for over 15 minutes or more.

9. Video traffic breakdown among sessions 10. Start-up delays

  • Two types of start-up delay:
    • the delay from when one channel is selected until the streaming player pops up;
    • the delay from when the player pops up until the playback actually starts.
  • The player pop-updelay is in general 10-15 seconds and the player buffering delay is around 10-15 seconds.
  • Therefore, the total start-up delay is around 2030 seconds.
  • Nevertheless, some less popular channels have a total start-up delays of up to 2 minutes.

11. Upload-download rates 12. Upload-download rates (cont) 13. Estimating the redundancy ratio

  • It is possible to download same video blocks more than once
  • Excluding TCP/IP headers, determine total streaming payload for the downloaded traffic.
  • Utilizing video traffic filtering heuristic rule (packet size > 1200B) extract video traffic.
  • Given playback interval and the media playback speed, obtain a rough estimate of the media segment size.
  • Compute the redundant traffic by the difference between the total received video traffic and the estimated media segment size.
  • Define redundancy ratio as ratio between redundant traffic and estimated media segment size.

14. Dynamics of video participants 15. Peer arrivals & departures 16. Geographic distribution of peers