A Network Policy is a set of rules governing the network. It can include traffic monitoring and controlling mechanisms. We should implement network policies in order to help implement QoS in a controlled manner. Network policies can also help with security implementations.
A Policy Decision Point (PDP) is the point in the network where decisions about policy are made. This is not to say that the PDP makes the policy – it just enforces them! A PDP can be almost any device in a network, including routers, switches, gateways, and servers. A PDP lets us enable multiple-media applications, WAN efficiency, and alignment of resources to business priorities, just name a few.
Policies are stored in a Policy Repository, which is an LDAP database. These policies are accessed by the PDP (sometimes referred to as a Policy Server). The PDP then distributes the policies to network devices, also referred to as Policy Enforcement Points. Typical policy management functions include:
1. Maximization of current bandwidth usage
2. Mapping network resources for increased performance without bandwidth cost
3. Identifying traffic flows for applications and services
4. Supporting advanced traffic prioritization
5. Administering rules or policies for network behavior
This is not a comprehensive list. There are many more functions of network policies, and I won’t begin to discuss them here. Nearly every corporation with a data or voice network has network policies. Often they are invisible to the end user; sometimes they are put in writing so that users can see them. Network policies are an excellent way to manage network traffic and should almost always be used to ensure Quality of Service.
Network management is also critical to network design. This includes the ability to manage individual devices on the network (with or without being physically present at the device), using fault management techniques, and identifying problems on a proactive basis. Of course, these are not the only things we need to think about when discussing network management, but they are very important. The last one is probably the most important – if we wait for a problem to arise before we fix it, we are asking for trouble. Fixing problems proactively is the key to ensuring network stability.