FST is used to monitor flows throughout the network, providing notification when flow limits are exceeded. Because issues tend to originate on ingress at the user edge, FST is ideally used to actively limit flows on user edge ports only. Actions taken on Inter-Switch Link (ISL) ports can be difficult to recover from. Creating too many flow monitors at the network core, and dropping flows, or disabling ports in the core, is not an optimal design strategy, and should be avoided.