Quality-of-Service (QoS) routing has the objective to find end-to-end paths that satisfy the service requirements of QoS flows. Efficient QoS routing requires accurate information about the QoS state of each router or link in a complete path. However, most currently deployed networks do not use accurate state information, or else, networks perform limited link-state measurements. In this paper, we propose a general measurement system, executed by routers, to accurately measure local link states. We select some existing measurement tools, designed for end-hosts, as possible choices for the implementation of our measurement system, and compare them through experimental evaluations. Also, we study the scheduling of measuring processes to reduce contention for network resources that may arise during the measurement time.