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Skype P2P

Skype P2P. Kedar Kulkarni 04/02/09. Goals. Study Skype working Study VOIP using P2P Use of P2P for VOIP Analyze effects of Churn Data for future P2P VOIP systems. Skype. Communication system VOIP IM File Transfer Video User Search Paid services. Skype P2P. Not much known

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Skype P2P

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  1. Skype P2P KedarKulkarni 04/02/09

  2. Goals • Study Skype working • Study VOIP using P2P • Use of P2P for VOIP • Analyze effects of Churn • Data for future P2P VOIP systems

  3. Skype • Communication system • VOIP • IM • File Transfer • Video • User Search • Paid services

  4. Skype P2P • Not much known • Similar to Kazaa • Hierarchical P2P • Supernodes/nodes • Login Server

  5. Basic Operation • Control Traffic / Media Traffic • Nodes connect to supernodes • Behind NAT and Firewalls • Host Cache • Supernode promotion • Supernode Relay • Robust • Encryption

  6. Skype User Search • Uses Global Index technology • Skype always could find an Online User • Search query sent to SN • SN returns 8 IPs of possible matches • if not found SN sends 24 next. And so on. • For SC behind NAT, SN will process the query • Login Server is the fall back option.

  7. Skype Calls • To call, calleeshould be in the friends list • If not, first search is done. • Public SCs • Caller establishes TCP connection with Callee • Caller behind NAT • Signaling information exchanged with SN first • Media flow between Caller and callee

  8. Calls • Caller and Callee behind NAT • Signaling information exchanged with SN • Media flow through relay

  9. Experiments • Supernode network activity • Observed a supernode for 135 days with 13GB of total data. • Supernode and client population • Obtained SN info from host cache • 250K total SNs found • Supernode Presence • Observed which SNs were online by sending ping msgs • 6000 random SNs at 30 min interval

  10. Characterization • Diurnal Behavior • Stable, than skype users clients

  11. Characterization • Fraction of supernodes joining or departing the network • Log­logplot of the complimentary CDF of supernode session times.

  12. Characterization • Semi­log plot of CDF of bandwidth used by the supernode • Geographic distribution of supernodes

  13. Comparison with other IMs

  14. Skype Supernode Map US: 83.7%, Asia8.9%, Europe 7.1%

  15. Conclusion • Diurnal, work-week behavior. • Similar to web browsing • Stability of SNs mitigates churn • SNs use little bandwidth, occasionally relay media and file transfer • Best Mouth to ear latency

  16. Papers • An Experimental Study of the Skype Peer-to-Peer VoIP System • S. Guha, Neil Daswani, and Ravi Jain • An Analysis of the Skype Peer-to-Peer Internet Telephony Protocol. • S.A.Baset and H.G. Schulzrine

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