According to one embodiment of the present invention, there is provided a system for allocating bandwidth in a network to a plurality of traffic classes. Each traffic class has a first bandwidth allocation. The system comprises a network manager which is configured to determine a bandwidth utilization for each traffic class, to determine an amount of unused network bandwidth, to calculate second bandwidth allocations for each traffic class by allocating a share of any determined unused network bandwidth between at least some of the traffic classes, and to update, in accordance with the second bandwidth allocations, a routing table accessible by routers in the network.