1.5 A Systems Methodology

We begin the network analysis process with a discussion about the systems methodology approach to networking. Applying a systems methodology to network analysis, architecture, and design is a relatively new approach, particularly in the Internet Protocol (IP) world. Systems methodology (as applied to networking) is viewing the network that you are architecting and designing, along with a subset of its environment (everything that the network interacts with or impacts), as a system. Associated with this system are sets of services (levels of performance and function) that are offered by the network to the rest of the system. This approach considers the network as part of the larger system, looking at interactions and dependencies between the network and its users, applications, and devices. As you will see, the systems methodology reveals interesting concepts that will be used throughout this book.

One of the fundamental concepts of the systems methodology is that network architectures and designs take into account the services that each network will provide and support. This reflects the growing sophistication of networks, which have evolved from providing basic connectivity and packet-forwarding performance to being a platform for various services. As discussed earlier, we are currently at the stage in network evolution where services are important to the success of many networks (third-generation networks). Some examples of third-generation networks are service-provider networks that support multiple levels of performance and pricing to its customers, contentdistribution networks that specialize in high performance transport, and enterprise networks that incorporate and apply billing and usage models to their customers.

When a network is viewed as part of a system that provides services, the systems methodology works quite well for a variety of networks, from small and simple to large, complex networks. It helps in determining, defining, and describing the important characteristics and capabilities of your network.