Software design style (2)

2. layered style:

Features:Search for components and connectors along the connection relationships from the components provided externally. If the topology is a directed acyclic graph (typically a linear structure ), the architectural style of this system is layered. This style facilitates the decomposition of complex systems, and also facilitates the replacement of components. As long as the interfaces are consistent, software at a certain layer can be replaced without affecting other parts of the system.

Typical applications:The most typical application is the International Standard Organization (ISO) Open Systems Interconnection (OSI) layer-7 network model. In addition, the kernel architecture of the Windows NT operating system is hierarchical (but not linear). It includes the system service layer, resource management layer, kernel layer, and hardware abstraction layer.

Note:

Advantages: The structure is clear and can be used for complex control.

Disadvantages: Low efficiency. In a layered structure, high-level data must be transferred and forwarded layer by layer to reduce system efficiency.

For this reason, the ISO/OSI Layer-7 model is rarely fully observed in practice. For example, the widely used TCP/IP protocol cluster only has a layer-4 structure.