DRAGO: Detecting, Quantifying and Locating Hidden Routers in Traceroute IP Paths

Traceroute is probably the most famous networking tool widely adopted in both industry and research. Despite its long life, however, measurements based on Traceroute are potentially inaccurate, misleading or incomplete due to several unresolved issues. In this paper, we face the limitation represented by hidden routers - devices that do not decrement the TTL, being thus totally invisible to Traceroute. We present, evaluate and release DRAGO, a novel active probing technique composed of three main steps. First, a novel Traceroute enhanced by the IP Timestamp option is launched toward a destination. Second, a procedure is applied to quantify the hidden routers contained in the path, if any. Third, a last procedure is performed to identify the exact position in the path of the detected hidden routers. Experimental results demonstrate that the phenomenon is not uncommon: DRAGO detects the presence of hidden routers in at least 6% of the considered Traceroute IP paths and limits the affected area to one fifth of the trace containing these devices.