Ojik

Topics: Transmission Control Protocol, OSI model, Internet Protocol Suite Pages: 55 (12486 words) Published: August 24, 2013
ISO/OSI Reference Model:

Open Systems Interconnection (OSI) is an effort to standardize networking that was started in 1977 by the International Organization for Standardization (ISO), along with the ITU-T.

The world has not always been so simple. Once upon a time, there were no networking protocols, including TCP/IP. Vendors created the first networking protocols; these protocols supported only that vendor’s computers, and the details were not even published to the public. As time went on, vendors formalized and published their networking protocols, enabling other vendors to create products that could communicate with their computers. For instance, IBM published its Systems Network Architecture (SNA) networking model in 1974. After SNA was published, other computer vendors created products that allowed their computers to communicate with IBM computers using SNA. This solution worked, but it had some negatives, including the fact that it meant that the larger computer vendors tended to rule the networking market.

A better solution was to create an open standardized networking model that all vendors would support. The International Organization for Standardization (ISO) took on this task starting as early as the late 1970s, beginning work on what would become known as the Open System Interconnection (OSI) networking model. ISO had a noble goal for the OSI model: to standardize data networking protocols to allow communication between all computers across the entire planet.

A second, less formal effort to create a standardized, public networking model sprouted forth from a U.S. Defense Department contract. Researchers at various universities volunteered to help further develop the protocols surrounding the original department’s work. These efforts resulted in a competing networking model called TCP/IP. By the late 1980s, the world had many competing vendor-proprietary networking models plus two competing standardized networking models. So what happened? TCP/IP won in the end. Proprietary protocols are still in use today in many networks, but much less so than in the 1980s and 1990s. The OSI model, whose development suffered in part because of a slower formal standardization process as compared with TCP/IP, never succeeded in the marketplace. And TCP/IP, the networking model created almost entirely by a bunch of volunteers, has become the most prolific set of data networking protocols ever.

▪ OSI provides standards and guidelines for network communication it defines all aspects of network communication. ▪ Osi model is only a logical concept (set of rules and regulations) ▪ Osi model is a layered model. Each layers has got it’s own functions. A group of functions put together is called a layer. ▪ Model defines the task to be performed on each network device

▪ Historically, OSI was the first large effort to create a vendor-neutral networking model, a model that was intended to be used by any and every computer in the world, many of the terms used in networking today come from the OSI model.

OSI model consists of 7 layers each layer performs set of predefined functions

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So with OSI Layer:

• Reduces complexity
• Standardizes interfaces
• Ensures interoperable technology
• Accelerates evolution
• Simplifies teaching and learning

Functions of layer in OSI Model:

Layer 7: The Application Layer
It’s closest to the user. This layer provides network services to the user’s applications. It differs from the other layers in that it does not provide services to any other OSI layer, but only to applications outside the OSI reference model. The application layer establishes the availability of intended communication partners and synchronizes and establishes agreement on procedures for error recovery and control of data integrity.

Layer 6: The Presentation Layer
The presentation layer ensures the information...
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