Abstract: One function of a communications network, or of nodes in such a network, is to gather data that is useful in assessing network performance, and quantifying metrics of node and/or network performance. Various embodiments disclosed herein improve the ability of nodes and networks to gather such data, and quantify metrics of node and/or network performance by selectively marking existing network traffic, and in preferred embodiments without having to dilute network traffic by generating and transmitting dummy data packets.