1.11 Conclusion

In this chapter you learned definitions of network analysis, architecture, and design; the importance of network analysis in understanding the system and providing a defensible architecture and design; and the model for the network analysis, architecture, and design processes.

You have also learned that networks are not independent entities but rather a part of the system and that the delivery of network services is a goal of the system. Network services consist of performance and function and are offered to users, applications, and devices so that they can accomplish their work on the system. In order to architect and design a network to support services, you need to know what they are, how they work together, and how to characterize them. Once you do this, you will have a broad view of what the network will need to support, which you can take to the next levels of detail as you proceed with the network analysis.

By describing the system as a set of components (e.g., user, application, device, network), you can apply interfaces between these components to help understand the relationships, inputs, and outputs between each of the components.

You have also learned about different types of services, from best-effort, unpredictable, and unreliable service to predictable, bounded, and somewhat predictable service, to guaranteed services with accountability.

To go to a level deeper in the discussion about services, we considered the service performance characteristics capacity, delay, and RMA (reliability, maintainability, and availability). These characteristics will be useful only if we can measure and verify their values in the system. We discussed these values, as well as service metrics, thresholds, and boundaries. We learned that performance characteristics could be combined into a performance envelope.

Having thought about systems, services, and their characteristics, we are now ready to quantify what we want from our networks. To do this, we first need to gather, analyze, and understand the requirements from the system. This is requirements analysis, the next step in the network analysis process.