- interface with the communications hardware and transmission medium. ƒ
- transmission of an unstructured stream of data bits.
Layer 2 - Data-link Layer ƒ
- transmission of frames containing data and/or control information. ƒ
- provides error control and flow control over the data link.
Layer 3 - Network Layer ƒ
- effective where the end-to-end path consists of a series of data links either within one subnetwork [WAN] or over a collection of subnetworks [internet]. ƒ
- provides routing and relaying over the subnetwork[s].
Layer 4 - Transport Layer ƒ
- provides a reliable end-to-end transfer of data between the two communicating systems. ƒ
- provides service independent of the underlying sub network[s]. ƒ
- acts as a separator between the end system related protocols [interworking] and the sub network related protocols [interconnection].
Layer 5 - Session Layer ƒ
- manages the session [establishment, dialogue exchange, recovery, termination].
Layer 6 - Presentation Layer ƒ
- resolves differences in data representation in end systems. ƒ
- provides common transfer syntax.
Layer 7 - Application Layer ƒ
- provides network services for user application processes. ƒ
- file transfer, remote terminal access, messaging, remote job entry, management, security and directory services.
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