A method of determining the latency of a route in a packet-switched network, a packet switch for use in such a method and network and a packet-switched network are disclosed. Preferably, each switch maintains a routing table that records the latency of the routes accessible by that switch. Each switch also preferably has a GPS-based universal time clock which it employs to time the transmission and arrival of identifiable timing packets, these times being used to compute route latency and to up-date the routing tables. In one example (FIG. 1) a packet-switched network has a plurality of switches (S1-S6) interconnected by links or trunks (T1-T7). A local GPS-base clock (GPS CLK) is connected to each switch (S1-S6) to enable the accurate timing of transmission and reception of identifiable timing packets in accordance with a system-wide universal timing standard.