Analysis of the Scalability of the Overlay Skype System

In this paper, the authors study the Skype system in order to determine the presence of bottleneck for its scalability. In fact, as the Internet grows and the number of Skype users increases constantly, the Skype traffic carried by network links grows and also the load of Skype super-nodes increases, mainly due to the need of relaying calls for users behind NAT restrictions. They model both the underlay Internet at the inter-Autonomous System level and the overlay Skype system.