A method for performing a performance measurement on a multipoint packet flow transmitted in a packet-switched subnetwork. A monitoring network of measurement points is implemented in the subnetwork. All packets have a marking value, which is periodically switched between first and second marking values. Each measurement point receiving a marked packet updates a couple of performance parameters, one per each marking value. Since not all the measurement points receive the same packets of the multipoint packet flow, to provide a performance measurement a cluster of measurement points is firstly identified in the monitoring network, which possesses the following property: each packet received at the input of the cluster is also received at the output of the cluster, if no packet loss occurs. The performance parameters provided by input and output measurement points of the identified cluster are then used for providing the performance measurements.