Protocol Design Concepts, IP and Routing

Protocols are complex, distributed pieces of software. Abstraction and modular design are standard techniques used by software engineers to deal with complexity. By abstraction, we mean that a subset of functions is carefully chosen and setup as a “blackbox” or module (see Figure 1). The module has an interface describing its input/output behavior. The interface outlives the implementation the module in the sense that the technology used to implement the interface may change often, but the interface tends to remain constant. Modules may be built and maintained by different entities. The software modules are then used as building blocks in a larger design. Placement of functions to design the right building blocks and interfaces is a core activity in software engineering.