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The Skype Network Ordinary Host (OH) A Skype client Super node (SN) A Skype client

The Skype Components Port No default listening port. Randomly chooses a port upon installation. Host cache (HC) IP address and port number of online Skype nodes Maximum size: 200 entries Codecs (GlobalIPSound) Wideband codecs (50-8,000 Hz)

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The Skype Network Ordinary Host (OH) A Skype client Super node (SN) A Skype client

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  1. The Skype Components • Port • No default listening port. Randomly chooses a port upon installation. • Host cache (HC) • IP address and port number of online Skype nodes • Maximum size: 200 entries • Codecs (GlobalIPSound) • Wideband codecs (50-8,000 Hz) • iLBC (packet size: 20 and 30 ms bitrate: 15.2 kb/s and 13.3 kb/s) • iSAC (packet size: 30-60 ms bitrate: 10-32 kb/s) • G.729 for SkypeOut? Skype Functions Summary Call Establishment An Analysis of the Skype Peer-to-Peer Internet Telephony Protocol Salman Abdul Baset and Henning Schulzrinne Internet Real-Time Lab, Columbia Universityhttp://www.cs.columbia.edu/~salman/skype/ Super Nodes • 8,153 login attempts over four days • 35% hostnames had a ‘.edu’ suffix • 102 universities • 894 unique SNs • Unique SN IP distribution: US 83.7%, Asia 8.9%, Europe 7.1% • Top 20 nodes received 43.8% of the total connections Experimental Setup The Skype Network • Ordinary Host (OH) • A Skype client • Super node (SN) • A Skype client • Has public IP address, ‘sufficient’ bandwidth, CPU and memory • Bootstrap super nodes (maintained by Skype) • Used when running Skype for the first time • A total of seven nodes hard-coded in Skype executable • Login server • Stores Skype id’s, passwords and buddy lists • Used at login for authentication • Version 1.4: 212.72.49.141 and 195.215.8.141 Skype Relay Experiments • Jan 20th to Feb 5th 2006..Caller and callee machines in IRT lab • 8,822 successful call attempts and 4,904 unique relay IP addresses • 60% of the calls routed through caller SN • Relay nodes in 51 countries Skype, MSN, Yahoo and Google Talk

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