The International Organization for Standardization (ISO) developed the Open Systems Interconnect (OSI) model, illustrated below, during the late 1970's. Eighty- three countries participated in the definition and acceptance of the international communications definition.

The European Community's (EC) decision to use the OSI Model as a basis for integrating the information systems from each member country is an example of the economic impact that can be wielded by a technology definition.

The expansion of Internet technologies has made the global economy accessible to anyone who wants to reach out and grasp it. Understanding the connectivity issues that the OSI model addresses will make you a stronger competitor because you will be able to leverage the available tools and technologies from an end-to-end perspective.

While a number of companies have endorsed and agreed to apply this model within their own products, few follow its guidelines exactly. Some use their own networking model, most of which closely parallel the OSI standard. Still, it is a helpful tool, allowing a common point of reference for discussing network devices and concepts.

Design principles

• Connection-oriented network layer
• Standardize all protocol aspects: SAP. PDU, procedures
• Confirmed interactions
• A single comprehensive standard per layer
• Conformance testing, formal specifications