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Computer Networks Bhushan Trivedi, Director, MCA Programme, at the GLS Institute of Computer Technology, Ahmadabad © Oxford University Press 2011 Chapter 1 Introduction to computer networks © Oxford University Press 2011 Questions to be answered • How is a file downloaded • How do emails reach their intended recipients? • How does a wired and a wireless connection work the same? • How is receipt of new data (for example a new antivirus update), handled and by whom? © Oxford University Press 2011 Layering Example © Oxford University Press 2011 Advantages of layers • • • • • Reducing the complexity Division of Work Standard Interfacing between Components Replacing a component is easy Independence in Protocol design © Oxford University Press 2011 Disadvantages of layers • Reduced Speed and Performance • Increased Memory usage • Sensor Networks Node © Oxford University Press 2011 Layers for OSI and TCP/IP © Oxford University Press 2011 Connection Oriented vs Connectionless • • • • • • • Connection establishment Complete line occupied or not Multiplexing Robustness of the connection Cost of the connection Quality of service Order of delivery © Oxford University Press 2011 Example CO vs CL © Oxford University Press 2011 OSI and TCP IP difference • OSI has seven layers, TCP/IP has five layers. • The OSI was connection-oriented, TCP/IP model was connectionless • The TCP/IP provided a choice (TCP or UDP) to the customers. • TCP/IP describes an existing set of protocols The OSI model was more general © Oxford University Press 2011 OSI and TCP IP difference • OSI model distinguishes between an interface and a protocol TCP IP does not • The OSI model clearly mentions the physical and data link layers. • The Internet provides both, connection oriented service over connectionless transfer and connectionless service over connectionless transfers, © Oxford University Press 2011 The Physical Layer © Oxford University Press 2011 The Data Link Layer © Oxford University Press 2011 The Network Layer © Oxford University Press 2011 Network Layer Functioning © Oxford University Press 2011 Routing at Network Layer © Oxford University Press 2011 Extracting Prefix © Oxford University Press 2011 Routing between different networks © Oxford University Press 2011 Transport layer and reliability by retransmitting © Oxford University Press 2011 Application Layer © Oxford University Press 2011 Other • Distributed Systems – WWW • Peer to peer networks • Client server networks © Oxford University Press 2011 X.25 © Oxford University Press 2011 DTE routing © Oxford University Press 2011