QRP08-5: Detection and Comparison of RTP and Skype Traffic and Performance

RTP and Skype applications generate a growing part of the Internet traffic, especially for users on ADSL because of flatrate tarification. In this study, we focus on these two main Voice over IP traffic protocols to characterize the utilization, the performance and the evolution of VoIP systems over six months. We start by identifying the traffic generated by Skype and other classical RTP applications. We thus characterize the traffic of these applications and identify some statistical behaviors. We then analyze in more details and compare the performance of RTP and Skype applications in order to evaluate their influence over the traffic. From ISPs point of view, recognizing these real time applications and analyzing their characteristics and performance is a determining factor for quality of service and troubleshouting. Our analysis is based on ADSL traffic captured at TCP/UDP level on a Broadband Access Server comprising thousands of users. Thus, using a flow-based analysis, we characterize and compare the VoIP traffic and users, and we draw interesting results on traffic patterns and inter-arrivals, connectivity between users, location of sources and performance limitations.