A Carrier Ethernet network comprises nodes connected by links. The network supports connectionless traffic flows between nodes. A network management system performs a method comprising: determining when an event has occurred in the network which may change bandwidth usage on a link of the network; determining traffic flows which use the link; determining a total bandwidth demand of the traffic flows using the link; and comparing the total bandwidth demand with a bandwidth capacity of the link. Determining when the event has occurred can include at least one of: receiving an alarm indicating a network fault; receiving a topology change indication from a node of the network.