Chapter 1B - Chapter 1 Part B Data Communications and...

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2.1 Chapter 1 Part B Data Communications and Networks Overview
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2.2 2-1 LAYERED TASKS 2-1 LAYERED TASKS We use the concept of We use the concept of layers layers in our daily life. As an in our daily life. As an example, let us consider two friends who communicate example, let us consider two friends who communicate through postal mail. The process of sending a letter to a through postal mail. The process of sending a letter to a friend would be complex if there were no services friend would be complex if there were no services available from the post office. available from the post office.
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2.3 Figure 2.1 Tasks involved in sending a letter
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2.4 2-2 THE OSI MODEL 2-2 THE OSI MODEL Established in 1947, the International Standards Established in 1947, the International Standards Organization ( Organization ( ISO ISO ) is a multinational body dedicated to ) is a multinational body dedicated to worldwide agreement on international standards. An ISO worldwide agreement on international standards. An ISO standard that covers all aspects of network standard that covers all aspects of network communications is the Open Systems Interconnection communications is the Open Systems Interconnection ( ( OSI OSI ) model. It was first introduced in the late 1970s. ) model. It was first introduced in the late 1970s.
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2.5 Motivation of OSI Model Provides a common set of convention , to make  communication among heterogeneous machines  possible.  If functions of each layer are well-defined,  standards can  be developed independently and simultaneously for each  layer  – that means faster standardization process.  If the boundaries between layers are well-defined,  changes in standards in one layer need not affect  another layer  – easier to introduce new standards the task of communication between applications on  different computer is too complex to be handle as a unit.  Problem can be decomposed into manageable parts
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2.6 ISO is the organization. OSI is the model. Note
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2.7 Figure 2.2 Seven layers of the OSI model
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2.8 Figure 2.3 The interaction between layers in the OSI model the same set of layered functions must exist in 2 systems (transmitting and receiving sides) communication is achieved by having The corresponding (peer) layers in 2 Systems communicate telecom networks mainly concern the lowest 3 layers
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2.9 Figure 2.4 An exchange using the OSI model
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2-3 LAYERS IN THE OSI MODEL 2-3 LAYERS IN THE OSI MODEL In this section we briefly describe the functions of each In this section we briefly describe the functions of each layer in the OSI model. layer in the OSI model.
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This note was uploaded on 08/27/2009 for the course FET etm taught by Professor Hi during the Spring '09 term at Multimedia University, Cyberjaya.

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Chapter 1B - Chapter 1 Part B Data Communications and...

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