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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
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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?
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Layering Example
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Advantages of layers
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Reducing the complexity
Division of Work
Standard Interfacing between Components
Replacing a component is easy
Independence in Protocol design
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Disadvantages of layers
• Reduced Speed and Performance
• Increased Memory usage
• Sensor Networks Node
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Layers for OSI and TCP/IP
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Connection Oriented vs
Connectionless
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Connection establishment
Complete line occupied or not
Multiplexing
Robustness of the connection
Cost of the connection
Quality of service
Order of delivery
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Example CO vs CL
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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
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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,
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The Physical Layer
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The Data Link Layer
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The Network Layer
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Network Layer Functioning
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Routing at Network Layer
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Extracting Prefix
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Routing between different networks
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Transport layer and reliability by
retransmitting
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Application Layer
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Other
• Distributed Systems
– WWW
• Peer to peer networks
• Client server networks
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X.25
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DTE routing
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