December 13, 2000, 3:51 PM — Network managers of global or multisite enterprises are all too familiar with the
degradation that affects networks as traffic volumes escalate. When competition for
bandwidth exists, there is no way to identify and assure the passage of
mission-critical data across a network. With multisite enterprises increasingly
dependent upon their network-intensive, mission-critical applications, unpredictable
performance is not acceptable.
Policy management is a way for network managers to automate administration of
quality-of-service facilities on the network. In a policy-based network management
system, you create policies that are simply rules for prioritizing traffic from certain
users and applications. The system also stores information about each network device's
capabilities. It converts the policies you enter to configurations for the routers and
other network devices that handle data traffic.
Most major equipment vendors, including
a>, 3Com, and
developed policy management systems for their products, but unfortunately none
interoperates with the others. A few independent companies such as href="http://www.orchestream.com/">Orchestream are attempting to build multivendor
systems, but even those companies support only one or two vendors, though more support
is promised down the road. However, as standards mature and vendors gain experience
working with them, we should begin to see interoperability improve.
If you define three classes of traffic priorities -- gold for SAP traffic, silver
for SNA, and best effort for everything else, for example -- then the system
distributes to the routers configuration files that describe how to process the three
classes. Network routers may be running different versions of an OS or may have
different queue sizes and traffic processing algorithms, so each of their configuration
files may be different. But you don't have to worry about that -- the policy management
system takes care of the details.
Many network managers go too far when attempting to define policies for the WAN.
They want to define policies for applications, departments, users, and specific days
and times. Even if today's routers can support that many policies, defining them still
isn't a good idea. Putting the burden on networking equipment to do that much packet
classification is counterproductive. The routers become so bogged down that every
application and user suffers with decreased performance.