Understanding the network.pdf - Back to Home

The Origins of the OSI-RM
The OSI-RM effort began in 1977 as a series of articles on the development of a
standard reference model for networking. In 1978, the OSI-RM was defined as a
standard by the International Standards Organization (ISO). The OSI-RM's purpose
is to provide a framework for visualizing the data communication process. After it's
described, it is then possible to segment this process into defined layers that
represent natural separations in the communication process as a whole. Standards
for how products and protocols should operate were specified so that the services at
each layer could function with the adjoining layers. The lower three layers address
host-to-host communications functions, and the upper four layers
host-to-application communications functions.
The protocols associated with the OSI-RM are known as the ISO protocol suite. The
ISO suite is entirely standards-based. These standards were developed by various
working groups within the ISO and the International Telecommunication Union
Telecommunications Standardization Sector (ITU-T), a UN treaty organization
made up of the world's telecommunication providers.
NOTE
ITU-T was originally known as the CCITT, or the Consultative Committee for
International Telegraph and Telephone.
It was widely believed that OSI-based protocol suites would replace the TCP/IP
protocol suite (and others), but this never happened. One reason it never happened
was the time it took for the standards to be developed. Although everyone who took
part could agree on the need for standards, getting everyone to agree on a specific
implementation was an entirely different story. The second reason was that they
encountered cost and interoperability problems. There are only 12 laboratories
accredited to certify products for OSI conformance, making for a slow and costly
development cycle. This additional cost was passed on to the customer. In addition,
although the products might have been tested and certified to meet the OSI
standard, this did not mean that they would integrate with each other. These
problems killed the OSI effort in the United States for the business sector.
However, for the U.S. government, OSI is not dead. All communications equipment
purchased by the U.S. government must be GOSIP (Government OSI Profile)
compliant (see Figure 1.13). In Europe, OSI product compliance was required early
on in the OSI standards development process. Because the U.S. government and
the European Union make up a rather large customer base, OSI has found its way
into many of the systems you already use. For example, if you are a Novell 4.x or 5.x