Lecture 10 - 11/14/2011 CNIT 17600 IT Architectures...

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11/14/2011 1 CNIT 17600 IT Architectures Networks Readings 2 Chapter 12 NOT 12.7 Computer Organization & Architecture
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11/14/2011 2 3 Become familiar with the general architecture of the Internet Objectives Become familiar with the fundamentals of network architectures Learn the basic components of a local area network 12.1 Introduction 4 The network is a crucial component of today’s computing systems Resource sharing across networks has taken the form of multitier architectures having numerous disparate servers Sometimes far removed from the users of the system If you think of a computing system as collection of workstations and servers, then surely the network is the system bus of this configuration
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11/14/2011 3 12.2 Early Business Computer Networks 5 The first computer networks consisted of a mainframe host that was connected to one or more front end processors Front end processors received input over dedicated lines from remote communications controllers connected to several dumb terminals The protocols employed by this configuration were proprietary to each vendor’s system One of these, IBM’s SNA became the model for an international communications standard, the ISO/OSI Reference Model 12.3 Early Academic and Scientific Networks 6 In the 1960s, the Advanced Research Projects Agency funded research under the auspices of the U.S. Department of Defense Computers at that time were few and costly. In 1968, the Defense Department funded an interconnecting network to make the most of these precious resources The network, ARPANet, had sufficient redundancy to withstand the loss of a good portion of the network Designed & implemented by Bolt, Beranek, and Newman, DARPANet, later turned over to the public domain, eventually evolved to become today’s Internet.
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11/14/2011 4 12.4 Network Protocols – OSI Model 7 To address the growing tangle of incompatible proprietary network protocols, the ISO formed a committee to devise a unified protocol standard (1984) The result of this effort is the ISO Open Systems Interconnect Reference Model The ISO’s work is called a reference model because virtually no commercial system uses all of the features precisely as specified in the model The OSI model does, however, lend itself to understanding the concept of a unified communications architecture The OSI RM contains seven protocol layers, starting with physical media definitions at Layer 1, through applications at Layer 7 8 12.4 Network Protocols – OSI Model
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5 OSI model defines only the functions of each of the seven layers and the interfaces between them Implementation details are not part of the model 9 12.4 Network Protocols – OSI Model The Physical layer receives a stream of bits from the physical media, processes them, then forwards them to the Data Link layer above The Physical layer receives a “chunk” of bits from the Data Link layer
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This note was uploaded on 01/30/2012 for the course CNIT 176 taught by Professor Hansen during the Fall '09 term at Purdue University-West Lafayette.

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Lecture 10 - 11/14/2011 CNIT 17600 IT Architectures...

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