Traffic Identification and Overlay Measurement of Skype

Nowadays many P2P applications over the Internet utilize sophisticated protocols and employ various techniques to avoid detection and recognition with standard measurement tools. The communication analysis of P2P network is significant for recognizing P2P traffic and managing P2P applications effectively. In this paper, Skype is studied as a case to identify P2P traffic and measure an overlay network of P2P system. Because Skype protocol is proprietary and its control information is encrypted, little is understood about Skype network. We analyzed large amounts of data of Skype traffic and extracted many application level signatures. Based on such signatures, we can identify Skype traffic, then an effective tool named Super Nodes Collecting and Probing Platform (SNCPP) was designed to measure the overlay of Skype network. The SNCPP probes online super nodes in real-time, and it displays the distribution in a three-dimensional world map. The results in this paper should be useful for future architects of P2P overlay networks as well as for network security management