Tracking Down Skype Traffic

Skype is beyond any doubt the most popular VoIP application in the current Internet application spectrum. Its amazing success drawn the attention of telecom operators and the research community, both interested in knowing Skype's internal mechanisms, characterizing traffic and understanding users' behavior. We dissect the following fundamental components: data traffic generated by voice and video communication, and signaling traffic generated by Skype. We use both active and passive measurement techniques to gather a deep understanding on the traffic Skype generates. From extensive testbed experiments, we devise a source model which takes into account: (i) the service type, i.e., voice or video calls (ii) the selected source Codec, (iii) the adopted transport-layer protocol, and (iv) network conditions. Furthermore, leveraging on the use of an accurate Skype classification engine that we recently proposed, we study and characterize Skype traffic based on extensive passive measurements collected from our campus LAN.