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Skype & its protocol

Skype & its protocol. Aaron Loar CPE 401. Introduction. Skype’s Background Topology 3 Node Types Questions. Background. Created in 2003 Same people as the makers of KaZaa Bought in 2005 by eBay Sold in 2009 Canada Pension Plan Investment Board Future uncertain. Overview.

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Skype & its protocol

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  1. Skype& its protocol Aaron Loar CPE 401

  2. Introduction • Skype’s Background • Topology • 3 Node Types • Questions

  3. Background • Created in 2003 • Same people as the makers of KaZaa • Bought in 2005 by eBay • Sold in 2009 • Canada Pension Plan Investment Board • Future uncertain

  4. Overview • Overlay network • Peer-to-peer • 3 types of nodes • Skype clients (SC) • Super nodes (SN) • Skype Login Server • Able to operate over low bandwidth • Offers IM chat, VoIP, Video chat, File sharing, …

  5. Skype Clients • Host Cache • Locally stored list of super nodes and ports • Locally stored Buddy List (Outdated) • Node cannot prevent Super Node promotion • Encrypted login • Listens on particular ports • Wideband CODECs

  6. Super Nodes • From P2P systems • Help guide traffic between clients • Global Indexing • Search for users • Users have no control over promotion • Store addresses and ports of clients • Uses AES 256-bit encryption

  7. Skype Login Servers • Controlled by Skype • Only communicate with clients for login • No traffic passes through SLS • Encrypted key generation

  8. Placing A Call • Real IPs = UDP • Voice packets = 67 Bytes • Use UDP as much as possible • Silent Packages • Little data about video protocols

  9. Conclusion • Skype’s History • Overlay Peer-to-peer topology • Skype Clients • Super Nodes • Skype Login Servers • Questions

  10. References • http://ezinearticles.com/?How-Skype-Works&id=496462 • http://www1.cs.columbia.edu/~library/TR-repository/reports/reports-2004/cucs-039-04.pdf • http://www.recon.cx/en/f/vskype-part1.pdf • http://www.recon.cx/en/f/vskype-part2.pdf • http://en.wikipedia.org/wiki/Skype_protocol

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