The rest of this paper is organized as follows: Section 2 gives an overview of related work. Next, Section 3 provides a brief overview of the bandwidth measurements methods commonly used in speedometers. Section 4 describes the experimental testbed used in the next sections. Then, we present the factor analysis, in Section 5, that includes operating system, CPU and memory occupancy. Section 6 presents a model to explain the influence of cross-traffic from other applications on the accuracy of packet-pair methods. Section 7 presents the QoS-Poll tool and describes the results obtained in a measurement campaign with real users. Finally, Section 8 summarizes our conclusions.