Operational Enviornments

1. Network Enviornment: concerned with protocols , exchange of messages, and standards relating to different types of underlying data communication networks.
2. OSI Enviornment: allows additional application-oriented protocols and standards to allow end-systems to communicate with one another in an open way.
3. Real Systems Enviornment: builds an OSI enviornment and is concerned with the manufacturers own propietary software and services, which have been developed to perform a particular distributed information processing task.

These envionments provide;

• well-defined interface between layers.
• function of layers , protocol defines the set of rules and conventions used by layer to communicate with a similar peer layer in another remote system.
• each layer provides a defined set of services to the layer immediately above it.
• uses those services immediately below to transport ,message units associated with the protocol to the remote peer layer.