On Modeling Round-Trip Time Dynamics of the Internet Using System Identification

Understanding the end-to-end packet delay dynamics of the Internet is of crucial importance since it directly affects the QoS (Quality of Services) of realtime services, and it enables us to design an efficient congestion control mechanism. In this paper, we measure the round-trip time, and build a mathematical model representing its dynamics using system identification. We first measure, as the input and output data for system identification, the packet inter-departure time from a source host and the corresponding round-trip time measured by the source host. ICMP (Internet Control Message Protocol) is utilized to measure the round-trip time for each packet. We next model the network, seen by a specific source host, as a dynamic SISO (Single-Input and Single-Output) system. Namely, the input to the system is the packet inter-departure time from the source host, and the output is the round-trip time variation between two adjacent packets. Using measurement results obtained from three different network configurations, we investigate how accurately the round-trip time dynamics of the Internet can be modeled with the system identification. key words: Round-Trip Time, Measurement-based Modeling, System Identification, ARX (Auto-Regressive eXogenous) Model