<b>1.</b>In [[telecommunication]], Thethe term '''open systems architecture''' means the layered hierarchical structure, [[configuration]], or model of a [[communications]] or distributed [[data processing]] [[system]] that (a) enables system description, design, development, installation, [[operation]], improvement, and [[maintenance]] to be performed at a given [[layer]] or layers in the hierarchical structure, (b) allows each layer to provide a [[set]] of accessible functions that can be controlled and used by the functions in the layer above it, (c) enables each layer to be implemented without affecting the implementation of other layers, and (d) allows the alteration of system performance by the modification of one or more layers without altering the existing equipment, procedures, and protocols at the remaining layers. ▼
In [[telecommunication]], the term '''open systems architecture''' has the following meanings:
<i>Note 1:</i> Examples of independent alterations include (a) converting from wire to optical fibers at a [[physical layer]] without affecting the data-link layer or the network layer except to provide more [[traffic capacity]], and (b) altering the operational protocols at the [[network]] level without altering the physical layer. ▼
▲<b>1.</b> The layered hierarchical structure, [[configuration]], or model of a [[communications]] or distributed [[data processing]] [[system]] that (a) enables system description, design, development, installation, [[operation]], improvement, and [[maintenance]] to be performed at a given [[layer]] or layers in the hierarchical structure, (b) allows each layer to provide a [[set]] of accessible functions that can be controlled and used by the functions in the layer above it, (c) enables each layer to be implemented without affecting the implementation of other layers, and (d) allows the alteration of system performance by the modification of one or more layers without altering the existing equipment, procedures, and protocols at the remaining layers.
<i>Note 2:</i> Open systems architecture may be implemented using the [[Open Systems Interconnection--Reference Model]] (OSI--RM) as a guide while designing the [[system]] to meet performance requirements.▼
▲<i>Note 1:</i> Examples of independent alterations include (a) converting from wire to optical fibers at a [[physical layer]] without affecting the data-link layer or the network layer except to provide more [[traffic capacity]], and (b) altering the operational protocols at the [[network]] level without altering the physical layer.
▲<i>Note 2:</i> Open systems architecture may be implemented using the [[Open Systems Interconnection--Reference Model]] (OSI--RM) as a guide while designing the [[system]] to meet performance requirements.
