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Convergence will live or die depending on how easy it is to implement IP-based QoS through policy-based networking. Unfortunately policy-based networking is still a work in progress.
Do you believe in convergence? More specifically, do you believe in a new world order in which voice, data and video all travel in harmony on high-speed IP networks?
If so, you also believe in policy-based networking. Convergence will ultimately succeed or fail based on the IP community's ability to implement quality of service (QoS) in a manageable, scalable fashion - and that's what policy-- based networking is all about.
A quick reality check indicates that the standards are still evolving, the protocols are untested and the products are immature. Policy-based networking won't be ready for prime time for another year or two. But it's not too early to start learning the basics of policy-based networking.
Policy: The basics
A policy defines how network resources are to be provisioned among network clients. Clients may be users, applications or hosts, and resources may be provisioned statically or dynamically based on factors such as time of day, resource utilization and client authorization rights.
A high-level policy statement, such as: "Provide Expedited Forwarding for all voice-over-IP traffic," is translated into a structured set of "if <condition(s)> then <action(s)>" rules so the policy can be stored, retrieved and interpreted by the various network components.
Unfortunately, first-generation systems generally will not interpret high-- level policy statements. Instead, the systems will require the network manager to enter policies as rules, such as:"if Port = HTTP (80) then set IP Precedence = 4".
Framework under construction
One of the most promising aspects of policy-- based networking is the work in progress at the Internet Engineering Task Force (IETF) to define a standard policy framework and a related set of protocols and schemas.
What has emerged is, at least on the surface, a relatively simple and elegant framework. The typical policy-based network will include:
* Policy entry console: a management tool through which the network manager defines and edits policies.
* Policy decision point (PDP): a policy server that retrieves policies from a repository and makes decisions on behalf of a Policy Enforcement Point (PEP).
* PEP: network devices, such as routers, switches and firewalls,...