Chapter 5. QoS and MPLS: Tools to Manage Application Performance

This chapter includes the following topics:

• Background

• Allocating network resources

• Traffic-handling mechanisms

• Provisioning and configuration mechanisms

• MPLS

• Traffic engineering

• Queuing mechanisms

• Integrated services

• Resource Reservation Protocol

• Differentiated services

Mission-critical applications, such as Oracle, Citrix, Microsoft Exchange, and the new breed of web-based applications, must perform well to ensure success in today's fast-paced environment. Bottlenecks may occur in many places, including the network. These bottlenecks often occur even though you have budgeted what you thought was more than adequate bandwidth for each application.

This is generally caused by a misperception of the application characteristics, including areas such as the base transaction (for example, number of turns, payload size, and so on), or by something more fundamental such as an increase in the number of users or an increase in the number of times each transaction is run.

Quality of service (QoS) is an umbrella term for a number of techniques that intelligently match the needs of specific applications to the network resources available. This is accomplished by accurately identifying the application descriptors and then allocating an appropriate amount of network resources such as bandwidth by relative application priority.

The result is that applications identified as business critical can be allocated the necessary priority and bandwidth levels to run efficiently. Applications identified as less than critical can be allocated best-effort bandwidth and will thus run at a lower priority.

This chapter does not attempt to detail the various intricacies and algorithms associated with the various protocols and mechanisms; such detail would draw focus away from the goal of optimizing application delivery. Instead, this chapter describes the various protocols and techniques used in the application delivery model. The chapter then covers allocation of network resources relative to application needs and the associated mechanism and protocols used by the infrastructure to deal with these needs. Finally, the chapter addresses the various characteristics of queuing and forwarding protocols engaged in the process.

If you do require specific protocol details, refer to the relevant organizations and standards, which are listed in Appendix A, "QoS-Related Requests For Comments," and Appendix B, "Guide to QoS Standards."