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Measurement of the main contributions to the single-hop delay introduced by an open-source router is dealt with. A new method is proposed, which is capable of distinguishing the time interval during which a generic packet stays in either input or output queue (queuing delay) of the router under analysis and the time interval characterizing the effective routing process (processing delay) the packet undergoes. Thanks to proper measurement probes, i.e., kernel-layer functions, the method makes the occurring time of events of interest available at the application layer, thus giving the possibility of separately evaluating the aforementioned delays and, ultimately, pursuing a deeper insight of the considered router. After brief remarks concerning various delays a packet experiences when passing through a generic router, the measurement principle underlying the method is presented in detail. Particular emphasis is put on its capability of locally monitoring the transit of each packet from the input to the output port of an open-source router along with main features and implementation issues of the proposed measurement probes. Results obtained in many experiments carried out on a suitable test bed in different operating conditions are then given in order to highlight the method's reliability and effectiveness.