Session Layer Definition

The session layer, the fifth layer from the bottom in the seven-layer OSI (open systems interconnect) model, establishes, manages (including providing security) and terminates connections between applications at each end.

The session layer contains fewer protocols and is less used than most of the other layers in the OSI model. In practice, it is often combined with the transport layer directly below it.

Session layer protocols are particularly useful for multimedia applications for which it is necessary to coordinate the timing of two or more types of data, such as voice and moving images, with a high degree of precision. Examples include video conferencing and streaming.

Examples of session layer protocols include DLC (data link control), PAP (printer access control), SMB (server message block), ASP (AppleTalk session protocol), NetBIOS (network basic input/output system) and ZIP (zone information protocol).

Created November 5, 2005.
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