Its goal is the interoperability of diverse communication systems with 7 layers of networking pdf protocols. The original version of the model defined seven layers.
A layer serves the layer above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that comprise the contents of that path. These two international standards bodies each developed a document that defined similar networking models. In 1983, these two documents were merged to form a standard called The Basic Reference Model for Open Systems Interconnection.
The standard is usually referred to as the Open Systems Interconnection Reference Model, the OSI Reference Model, or simply the OSI model. Basic Reference Model or seven-layer model, and a set of specific protocols. The new design was documented in ISO 7498 and its various addenda. In this model, a networking system was divided into layers. Within each layer, one or more entities implement its functionality.
Each entity interacted directly only with the layer immediately beneath it, and provided facilities for use by the layer above it. Protocols enable an entity in one host to interact with a corresponding entity at the same layer in another host. N was one of the seven layers of protocols operating in the local host. The OSI standards documents are available from the ITU-T as the X. Some of the protocol specifications were also available as part of the ITU-T X series.