Basic details about computer networks and layers of reference models

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Computer NetworksComputer Networks
Bhushan Trivedi, Director, MCA
Programme, at the GLS Institute of
Computer Technology, Ahmadabad

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Chapter 1Chapter 1
Introduction to computerIntroduction to computer
networksnetworks

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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
• 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
• 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