Policy-based management involves the following:
Although the practice of defining computing policies has been around for decades, the idea is relatively new with distributed networks. Not until recently have networking technologies become sophisticated enough to implement, enforce, and report on policy-related functionality.
Voice and video over packet networks have driven the need for QoS, which in turn has driven the need for policy-based management tools. QoS can be difficult to implement and maintain across large numbers of switches and routers. Policy-based management tools can simplify the consistent implementation and management of QoS-related features.
Policy-based management does not necessarily simplify the task of network-wide device configuration and validation. The configuration changes that policy software make to network devices can be quite complex and possibly destructive to the normal operation of the network. Before using policy-based configuration tools, you should learn the underlying technologies the tool configures on the devices.
At the time of this writing, few policy-based tools have been released, partly due to the complexity of developing such tools and partly due to their potentially destructive nature to networks.