1. A method of identifying a cause of performance degradation in a network, said method comprising: receiving, from the network, a first set of routing tables, wherein the first set of routing tables represent a current state of the network based on entries that indicate a next hop and a metric for a destination; determining a second set of routing tables based on simulating changes to the first set of routing tables to a steady-state condition; identifying a cause of performance degradation in the network based on differences between the entries in the first and second set of routing tables; and outputting information indicating the cause of performance degradation; wherein identifying the cause of performance degradation in the network comprises identifying at least one of: at least one difference between at least one next hop in the first set of routing tables and a corresponding next hop in the second set of routing tables; and at least one difference between the metric for a destination in the first set of routing tables and a corresponding metric in the second set of routing tables.