Several techniques have been proposed for measuring network-internal delays. However, those that rely on router responses have questionable performance, and all proposed alternatives require either new functionality in routers or the existence of a measurement infrastructure. In this paper we revisit the feasibility of measuring network-internal delays using only existing infrastructure, focusing on the use of ICMP Timestamp probes to routers. We present network measurements showing that ICMP Timestamp is widely supported and that TTL-responses often perform poorly, and we analyze the effect of path instability and routing irregularities on the performance and applicability of using ICMP Timestamp. We also confirm that router responses rarely introduce errors in our measurements. Finally, we present a practical algorithm for clock artifact removal that addresses problems with previous methods and has been found to perform well in our setting
