Network Warrior

Chapter 30. Designing a QoS Scheme

Designing a QoS scheme can be a relatively simple task, or a very large project. The scale of the solution depends on the complexity of your network, and the needs of your business. As a general rule, I like to plan everything I do with an end state design in mind. Even if I'm implementing a QoS scheme for a company that currently doesn't have VoIP, I'll design a scheme that assumes VoIP is coming in the future.

In this chapter, I'll walk you through designing a QoS scheme for a network that will require VoIP. Designing QoS is a two-part process: first, you must determine the requirements for the system, and then you have to configure the routers. We'll use low-latency queuing (LLQ), which is the recommended solution according to Cisco.

Determining Requirements

The first part of the QoS design process will require some investigative work on your part. You should interview all the business groups that use the network, and determine what protocols are important to them. Assume from the onset that every one of them will tell you that their protocols are the most important, and should get the lion's share of the bandwidth. You will need to assimilate all of this data, and make some decisions about how to allocate the bandwidth. With the help of good management, you should be able to come up with a list of requirements from which you can work.

Protocols

Compile a list of the protocols in use on your network. Tools to help you with this task include packet-capture ...