On the Performance of Round Trip Time Network Tomography

Network tomography is an appealing method for active measurement of link level characteristics such as delay and loss on end-to-end paths. Most network tomography techniques developed to date are based on one-way measurements requiring collaboration from both sending and receiving hosts which severely limits the scope of the paths over which these techniques can be used. We extend our previous work on Network Radar, a new tomographic inference method based on round trip time (RTT) measurements from TCP SYN/SYN-ACK packets. In this paper, our contributions are three-folded. (1) We extend our analytic framework for estimating delay variance on the shared network segment using Network Radar to include confidence estimates which enable measurement accuracy to be assessed - an important consideration for practical deployment. (2) We evaluate Network Radar in a series of experiments conducted in a controlled laboratory environment. These tests explore the boundaries of effectiveness of our RTT-based method, and show that it works well over a wide range of traffic conditions. (3) We evaluate Network Radar in a series of tests conducted in the wide area Internet. These tests show that RTT-based delay variance estimates can be used effectively to identify most likely network topology - a natural and verifyable application for RTT tomography. The performance results in this paper demonstrate that Network Radar can now be used for both research and operational purposes.