Chapter 9: Quality of Service(QoS)

The CCNP Exam Topics Covered in This Chapter Include the Following:

• Describe the needs of isochronous voice traffic on a switched data network

• Understand QoS solutions to voice quality issues such as jitter and delay

• Configure QoS features on multilayer switched networks

• Describe the general design models for switched networks requiring integrated IP telephony

• Plan the implementation of QoS features in a multilayer switched network

• Configure router redundancy using HSRP and VRRP, and verify operation

• Explain how both hardware and software redundancy is achieved in a multilayer switched network

• Understand the general design models for switched networks requiring integrated IP telephony

• Understand transparent LAN services and explain their use in service provider networks

• Configure load balancing using GLBP and SLB, and verify operation

• Implement QoS features in a multilayer switched network

Quality of service (QoS) is a largely new concept to bring into the world of LANs. Traditional Ethernet networks have been constructed on base protocols that allow for best efforts delivery and little else. Legacy switched networks-if you will pardon the term-have been designed and built using the same principles. After all, Ethernet suffers from collisions, broadcasts are LAN- wide random events, and frame sizes are unpredictable. All of this pretty much guarantees that quality of service will also have some random aspects, doesn't it?

Well, maybe not. Over the last few years, considerable effort has been applied to the development of techniques designed to provide the Internet Protocol (IP) with some added bells and whistles. Many of these are associated with providing quality of service beyond the best efforts nature of IP, in order to make the Internet a better place for the transport of time-sensitive traffic, such as voice, video, and multimedia applications.

Once these developments started to bear fruit, much of the effort shifted away from IP toward the edges of the networks. The idea is that if we can somehow create QoS-based switched networks in the campus, then it might be possible to create end-to-end QoS provision from LAN to LAN across the Internet.

This chapter deals primarily with the QoS options currently available on Cisco switches. We will have to start, however, with some detail about the QoS options in IP, so we can see how they may also be employed in multi-layer switched networks and how the layer 3 and layer 2 QoS options map together at the campus edge.

In the last section, "Redundancy in Switched Networks," we will look at redundancy in several of its implementations, including router redundancy and server redundancy. Although these techniques may not normally be considered QoS protocol, they do nonetheless add to the general availability of network services. The chapter will end with a brief discussion of one of the more interesting technologies to emerge from the new-look Ethernet, transparent Ethernet.