<
networking> (
OSI-RM,
OSI Reference Model, seven layer model)
A model of network architecture and a suite of
protocols (a
protocol stack) to implement it, developed by
ISO in 1978
as a framework for international
standards in heterogeneous
computer
network architecture.
The
OSI architecture is split between seven
layers, from
lowest to highest: 1
physical layer, 2
data link layer, 3
network layer, 4
transport layer, 5
session layer, 6
presentation layer, 7
application layer.
Each layer uses the layer immediately below it and provides a
service to the layer above. In some implementations a layer
may itself be composed of sub-layers.
OSI is the umbrella name for a series of non-proprietary
protocols and specifications, comprising, among others, the
OSI Reference Model, ASN.1 (
Abstract Syntax Notation 1), BER
(
Basic Encoding Rules),
CMIP and
CMIS (Common Management
Information
Protocol and Services),
X.400 (Message Handling
System, or MHS),
X.500 (Directory Service),
Z39.50 (search
and retrieval
protocol used by
WAIS), and many others.
Apart from its actual application to real protocols, it also
serves as a useful teaching model.
(2004-02-13)