Abstract: A method is presented of probing a network using probing with a probe packet pair, the pair comprising a first probe packet (L1) and a second probe packet (L2), and wherein L1>L2. The L1 probe packet is transmitted before L2 and the probe packets are arranged to be back-to-back on the last link. Use of the method provides the capacity of the last link in the probed path. The method may be run from a gateway in a network to probe aspects of the network and is suitable for probing a domestic network behind a home gateway. A use for the method is also described.