sixlayer

Sixlayer is a term used in information technology to describe a six-layer architectural model that organizes system components into six distinct layers to promote separation of concerns and interoperability. A common formulation defines the six layers as Physical, Data Link, Network, Transport, Session, and Application. In this arrangement, the lower layers handle media access and routing, while the upper layers govern data formatting, interfaces, and service exposure. The Presentation layer is typically merged into the Application layer in this model, reflecting a practical consolidation of encoding and user-facing logic.

Sixlayer is not standardized in the same way as the seven-layer OSI model. It appears in educational materials, industry literature, and vendor architectures as a simplified framework that sits alongside traditional protocol stacks. Because the model is not formal, different sources may rename or reorganize layers to suit a given technology stack.

Variations exist in how closely sixlayer maps to OSI. Some diagrams maintain a separate Session layer but collapse Presentation into Application; others combine Application and Presentation into a single top layer, or adjust layer names to emphasize APIs, services, or data contracts. The model is mainly used as an abstraction to discuss cross-layer responsibilities rather than a strict protocol specification.

Applications and domains include network architecture discussions, middleware design, cloud service architectures, data processing pipelines, and API-driven systems. Advocates cite benefits such as clearer interfaces between layers, easier testing, and flexibility in deploying components across distributed environments.

See also: OSI model, TCP/IP model, layered architecture, software architecture.