Chapter 3: Introduction to Protocols

Chapter 3: Introduction to Protocols

The Need for Protocols

To provide shared access to information and resources, as described in the preceding chapters, LANs must deliver information that is correct, in proper time sequential order, and understood by the recipient. To accomplish these functions, electrical circuits, error detection systems, error correction systems, information coding, data flow control, data formatting systems, and other hardware/software subsystems must all perform in a cooperative fashion following a set of rules or ?protocols.?

Dictionaries define ?protocol? as the set of rules and ceremonies by which diplomats and heads of state communicate. The rules of diplomatic protocol ensure that communications are completely and correctly understood by both parties. In data communication, protocols perform a similar function, and their use is almost as complex as the use of diplomatic protocols.

As indicated above, many functions must be performed to accomplish the task of data communication, and there is generally a protocol for each of these functions. A complete family of protocols is necessary to do the complete job. To assist people in designing protocol families, the International Standardization Organization (ISO) has developed a model in which each protocol is a ?layer? that performs certain functions for the protocol (layer) above it. This model is referred to as the OSI (Open Systems Interconnection) Reference Model. The OSI model, it should be emphasized, does not specify the exact details of each protocol; rather, it specifies a way of designing protocol families , i.e., what layers should be present and...

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Local Area Networks: An Introduction to the Technology

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Chapter 3: Introduction to Protocols

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