A common approach in solving complex engineering problems is to break them into smaller problems and solve each one separately. Unlike some complex systems, such as an airplane, which consists of almost independent subsystems (fuselage, wings, engine, navigation, etc.) that can be designed independently, network components are interconnected and cannot be easily designed independently. However, large networks can be broken down into smaller pieces using one or more of the following criteria:
- OSI layer
- Span or scope (LAN/MAN/WAN)
- Service type (Access/Transport)
- Medium (Wired/Wireless)
- Environment (Indoor/Outdoor)
- User/node mobility
- Security level
- Service level
Breaking down the design problem along the physical/logical boundaries, for example, allows creating layers of virtual topologies on top of a single physical topology. This also allows the design task to be carried out by different teams of experts as required.
There are also a distinct set of challenges and design solutions that differentiate between LAN and WAN designs. Similarly, designing an outdoor network has to consider environmental factors that are not present in indoor networks (weather conditions, locations, etc.)
The divide-and-conquer concept is closely related to the modularity concept (discussed later). Network designers often break up a network into small modules to facilitate better scalability, manageability, and security. These modules can be designed independently based on the services they provide.
Read about other Network Design Principles.