This chapter illustrates some of the performance and accounting features explained in Part II of this book. The structure is based on a series of questions that network operators ask:
"How do I check the device's health in the network?"
"How do I evaluate the link capacity?"
"When should links be upgraded?"
"How do I verify network connectivity?"
"How do I evaluate the response time between locations?"
"How do I ensure VoIP quality?"
"How do I determine the application types in the network?"
"How do I discover the traffic sent to and received from the Internet?"
These questions start with the simple ones about device and link availability and go up to the complex ones related to network-wide connectivity, type of applications in the network, and VoIP quality assessment. This chapter answers these questions by applying the mechanisms proposed in Part II of this book. In some cases, the example tells you the related chapter where detailed examples are given. In other cases, a full example including the configuration illustrates the point. Sometimes screenshots of network management applications display the answer to the question.
Figure 13-1 serves as the basis for this case study. It represents the different components of an enterprise network from a high-level point of view: a connection to the Internet with a potential backup, different branch locations connected over a wide-area network (WAN), a series of enterprise-wide application servers in the data center, the Network Management Station (NMS), and some VoIP traffic.