A network path is a path that a packet takes to reach its target. However, determining the network path that a host uses to reach it's target from the viewpoint of the latter is less trivial than it appears. Tools such as Traceroute allow the user to determine the path towards a target (i.e. the forward path), but not the path from the target to the source (i.e. the reverse path) due to routing asymmetry. Routing asymmetry means that the network path between two hosts may be different in opposite directions. Although previous studies have shown that this asymmetry is widespread, a more detailed characterization is lacking. In this paper routing asymmetry is investigated in depth using large scale measurements with 4.000 probes distributed world wide. The main goal of this paper is to provide characteristics about Internet asymmetry based on recent large scale measurements. Our findings contribute to a conclusive overview of Internet asymmetry, which assist researchers and engineers in making valid assumptions about routing asymmetry.
['Wouter de Vries', 'José Jair Santanna', 'Anna Sperotto', 'Aiko Pras']
How asymmetric is the Internet? A Study to Support the use of Traceroute