Editing Open systems architecture (section)

==Telecommunications==
In [[telecommunications]], open systems architecture (OSA) is a standard that describes the layered hierarchical structure, [[computer configuration|configuration]], or model of a [[information transfer|communications]] or distributed [[data processing]] [[system]]. It enables system description, design, development, installation, operation, improvement, and [[repair and maintenance|maintenance]] to be performed at the [[abstraction layer]]s in the hierarchical structure. Each layer provides a set of accessible functions that can be controlled and used by the functions in the layer above it. Each layer can be implemented without affecting the implementation of other layers.  The alteration of system performance by the modification of one or more layers may be accomplished without altering the existing equipment, procedures, and protocols at the remaining layers.{{Sfnp|General Services Administration|1991}}

Examples of independent alterations include the conversion from wire to optical fiber at a [[physical layer]] without affecting the [[data link layer]] or the [[network layer]], except to provide more [[throughput|traffic capacity]], and the altering of the operational protocols at the [[telecommunications network|network]] level without altering the physical layer.{{Sfnp|General Services Administration|1991}}