1 / 29

An Experimental Study of the Skype Peer-to-Peer VoIP System

An Experimental Study of the Skype Peer-to-Peer VoIP System. Saikat Guha, Cornell University Neil DasWani, Google Ravi Jain, Google IPTPS ’ 06 Presenter: Te-Yuan. What do they want to know?. What makes Skype so successful? Compare with File-sharing P2P network By Observing Skype ’ s

terrel
Download Presentation

An Experimental Study of the Skype Peer-to-Peer VoIP System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. An Experimental Study of the Skype Peer-to-Peer VoIP System Saikat Guha, Cornell University Neil DasWani, Google Ravi Jain, Google IPTPS’06 Presenter: Te-Yuan

  2. What do they want to know? • What makes Skype so successful? • Compare with • File-sharing P2P network • By Observing Skype’s • User behavior • Node Session Time • Overlay Network Traffic • SuperNode overlay network • Overall utilization & resource consumption

  3. Skype • Three Services • two-way audio streams & conference call up to 4 users • Instant Message • file-transfer • Structure • Alike KaZaA – SuperNode-based • Ordinary Node (ON) • Super Node (SN)

  4. Outline - Experiments • Expt. 1: Basic operation • Expt. 2: Promotion to supernode • Expt. 3: Supernode network activity • Expt. 4: Supernode and client population • Expt. 5: Supernode presence

  5. Expt. 1: Basic operation • To Answer: How do two Skype clients connect to each other? • Normally, • ON send control traffic through SN-p2p • Including • Availability information • Instant messages • Request for VoIP & File-transfer • What if ON is behind NAT/Firewall?

  6. Expt. 1: Basic operation – Cont. • NAT Traversal in Skype: • Level 0: Initiator NAT’ed • Level 1: Recipient NAT'ed • Level 2: Both NAT'ed (well-behaved NATs) • Level 3: Both NAT'ed

  7. Expt. 1: Basic operation – Cont. • Level 0: Initiator NAT’ed

  8. Expt. 1: Basic operation – Cont. • Level 1: Recipient NAT’ed

  9. Expt. 1: Basic operation – Cont. • Level 2: Both NAT'ed (well-behaved NATs)

  10. Expt. 1: Basic operation – Cont. • Level 3: Both NAT'ed

  11. Expt. 1: Basic operation – Cont. Level 0 Level 1 Level 2 Level 3

  12. Outline - Experiments • Expt. 1: Basic operation • Expt. 2: Promotion to supernode • Expt. 3: Supernode network activity • Expt. 4: Supernode and client population • Expt. 5: Supernode presence

  13. Expt. 2: Promotion to supernode • To Answer: What kind of node will be promote to SN? • Setup several Skype clients • One behind a saturated network uplink • One behind a NAT • One with a 10 Mbps connection & public IP • Key to be SN • plenty of spare bandwidth • publicly reachable

  14. Outline - Experiments • Expt. 1: Basic operation • Expt. 2: Promotion to supernode • Expt. 3: Supernode network activity • Expt. 4: Supernode and client population • Expt. 5: Supernode presence

  15. Expt. 3: Supernode network activity • Goal: To observe the network traffic of a Skype supernode • Duration: 135 days (Sep. 1, 2005 to Jan. 14, 2006) • Data captured: 13GB with ethereal

  16. Expt. 4: Supernode and client population • Goal: Collect SN & client IP/port • Duration:2005/7/25 – 2005/10/12 • Result: • Crawl 150K SN • Collect 250K SN info

  17. Expt. 4: Supernode and client population Connect to a SN A list of SN Save the list Connect to a SN from the list A list of SN

  18. Expt. 4: Supernode and client population • Collect client info • Collect the number reported by skype client

  19. Expt. 5: Supernode presence • Goal: how many SN online at a give time • Flow • Randomly Select 6000 SN - from the list collected by expt. 4 • Send “application-layer Ping” • Repeat every 30 mins for a month

  20. Expt. 5: Supernode presence - Cont Num. of SuperNode is more Stable diurnal behaviorof SN Weekend

  21. Expt. 5: Supernode presence - Cont • Geographic Distribution of Active SuperNodes 15-25% 20-25% 45--60% peak at 11am UTC (Europe mid-day)

  22. Expt. 5: Supernode presence - Cont • SuperNode Session Time Median is 5.5h

  23. Expt. 5: Supernode presence - Cont • Fraction of supernodes joining or departing Node arrival concentrated toward morning Skype usage is correlated with working hours Different from P2P file-sharing Node departureconcentrated toward evening

  24. Expt. 5: Supernode presence - Cont • Node Arrival dependent on Time • Not Poisson or Uniform process • Poisson process with varying hourly rate Node arrival concentrated toward morning Node departureconcentrated toward evening

  25. VoIP in Skype: Preliminary Observation 90.4%SN no need to relay VoIP traffic • SuperNode Traffic

  26. VoIP in Skype: Preliminary Observation • VoIP Relayed Session Arrival Behavior • Inter arrival time of Relayed VoIP/File sessions may be Poisson

  27. VoIP in Skype: Preliminary Observation • VoIP Session Length Behavior Skype: Median: 2m50s Average: 12m53s Longest: 3h 26s Traditional: Average: 3m Fraudulent: Average: 9m

  28. VoIP in Skype: Preliminary Observation • File-transfer sizes File size: Median: 346kB

  29. Conclusion • First measurement study of Skype VoIP system • Skype differs significantly from file-sharing P2P • User Behavior • Diurnal & Work-week • Calls are significantly longer • File transferred are significantly smaller • SuperNode of Skype • Consume little bandwidth • Relatively stable

More Related