Layers of the OSI Model

Application

Presentation

Session

Transport

Network

Data link

Physical


OSI Application Layer

Provides access to the OSI environment for users

Provides distributed information services


OSI Presentation Layer

Provides independence to the application processes from differences in data representation (syntax)


OSI Session Layer

Provides the control structure for communication between applications

Establishes, manages, and terminates connections (sessions) between cooperating applications


OSI Transport Layer

Provides reliable, transparent transfer of data between end points

Provides end-to-end error recovery and flow control


OSI Network Layer

Provides upper layers with independence from the data transmission and switching technologies used to connect systems

Responsible for establishing, maintaining, and terminating connections


OSI Data link Layer

Provides for the reliable transfer of information across the physical link

Sends blocks (frames) with the necessary synchronization, error control, and flow control


OSI Physical Layer

Concerned with transmission of unstructured bit stream over physical medium

Deals with accessing the physical medium

Mechanical characteristics

Electrical characteristics

Functional characteristics

Procedural characteristics