The document is an introductory lecture on computer networks, outlining key concepts such as network types, communication models, and protocol stacks. It discusses the importance of resource sharing, types of networks based on distance and access techniques, and the layered architecture of protocols. Additionally, it compares the OSI and TCP/IP reference models, detailing the functions of various layers involved in data transmission.

1. Computer Network Course
Lecture 1
Introduction

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Computer Network
Why network
Communications Model
Network types
Network Software
Layering
Protocol
Stack models
A network is a set of devices (often referred to as nodes) connected
by communication links. A node can be a computer, printer, or any
other device capable of sending and/or receiving data generated by
other nodes on the network. A link can be a cable, air, optical fiber,
or any medium which can transport a signal carrying information.

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Why Network
Resource Sharing
Reliability and Availability
Communication Medium
Access Information
E- Commerce
Person to Person Communication
Others

4. Some of Network applications
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A Communications Model
Source
generates data to be transmitted
Transmitter
Converts data into transmittable signals
Transmission System
Carries data
Receiver
Converts received signal into data
Destination
Takes incoming data

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Simplified Communications Model - Diagram

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Simplified Data Communications Model

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Types of Networks
Classification according to the covered distance

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Type of Networks
Classification according to the access techniques
Point to Point (Switched) Network
• Circuit switched networks
• Packet switched networks
Broadcast Network
• Local Area Networks
• Wireless LAN
• Satellite networks

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Type of Networks:

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Broadcast Networks

13. Network Software
Protocol Hierarchies
Design Issues for the Layers
Connection-Oriented and Connectionless Services
Service Primitives
The Relationship of Services to Protocols

14. Protocol
Key Features of a Protocol
Syntax
• Concerns the format of the data blocks
• Indicates how to read the bits - field delineation
Semantics
• Includes control information for coordination and error handling
Timing
• Includes speed matching and sequencing

15. Protocol Hierarchies
Layers, protocols, and interfaces.
The job of sending
message from source to
destination would be
complex without divided
the job into tasks, using
the concept of Layers

16. Protocol Hierarchies
Example: information flow

17. Design Issues for the Layers
Addressing
Error Control
Flow Control
Multiplexing
Routing

18. Connection-Oriented and Connectionless Services
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Unacknowledged connectionless service.
Acknowledged connectionless service.
Acknowledged connection-oriented service.
Connection-Less
Connection
Oriented
AcknowledgedUN-Acknowledged
“Best Effort” Better Quality
Reliable Delivery

19. Service Primitives
Five service primitives for implementing a simple
connection-oriented service.

20. Service Primitives
Packets sent in a simple client-server interaction
on a connection-oriented network.

21. Relationship of Services to Protocols

22. Reference Models
The OSI Reference Model
The TCP/IP Reference Model
A Comparison of OSI and TCP/IP

23. The OSI reference model.

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OSI Application Layer
Provides access to the OSI environment for users
Provides distributed information services
OSI Presentation Layer
Provides independence to the application processes from
differences in data representation (syntax)
OSI Session Layer
Provides the control structure for communication between
applications
Establishes, manages, and terminates connections (sessions)
between cooperating applications

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OSI Transport Layer
Provides reliable, transparent transfer of data between end points
Provides end-to-end error recovery and flow control
OSI Network Layer
Provides upper layers with independence from the data
transmission and switching technologies used to connect systems
Responsible for establishing, maintaining, and terminating
connections
OSI Data link Layer
Provides for the reliable transfer of information across the
physical link
Sends blocks (frames) with the necessary synchronization, error
control, and flow control

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OSI Physical Layer
Concerned with transmission of unstructured bit stream over
physical medium
Deals with accessing the physical medium
 Mechanical characteristics
 Electrical characteristics
 Functional characteristics
 Procedural characteristics

27. The TCP/IP reference model.
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28. Protocols and networks in the TCP/IP model
initially.

29. The reference model to be used in this course.
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