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More about Skype

More about Skype. Overview. Any node with a public IP address having sufficient CPU, memory and network bandwidth is a candidate to become a super node A peer cannot control whether it becomes a SN

laurel-morales
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More about Skype

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  1. More about Skype

  2. Overview • Any node with a public IP address having sufficient CPU, memory and network bandwidth is a candidate to become a super node • A peer cannot control whether it becomes a SN • An ordinary host must connect to a super node and must register itself with the Skype login server

  3. Techniques used in Skype • Firewall and NAT traversal • SC uses a variation of the STUN and TURN protocols to determine the type of NAT and firewall • Global decentralized user directory • Intelligent routing (fast switching) • Security (encryption) • Super-simple UI • Impact on fixed-line operator and mobile phone operator

  4. More Details • The Skype protocol is encrypted, so it is not possible to truly “reverse engineer” it, but guess what it does • A case study: Baset and Schulzrinne, “An analysis of the Skype peer-to-peer Internet telephony protocol”, Infocom 2006 • Super node • A few special “bootstrap” SNs help SC find login server • A SN helps a SC determine whether it is behind NAT or UDP-blocking firewall • A SN helps a SC search a user • Any user logged in during the last 72 hours can be found • This is validated by the paper • A SN helps two SC behind firewalls to relay voice packets

  5. Number of SN seen After 8163 successful logins

  6. Distribution of SNs Note, majority (83.7%) found in US

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