Introduction to Computer Networks

• Definition:

  A computer network is a set of devices (nodes) like computers, printers, etc., connected by communication channels to share data. Example: Internet.

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  ⚠️ Note: A network ≠ distributed system (which has one control unit and multiple dependent systems).

Criteria for a Good Network

1. Performance – measured by:
   • Also depends on software efficiency, number of users, hardware capability.
   • Transit time (time to travel a message)
   • Response time (time between query & reply)
2. Reliability – fewer failures = higher reliability.
3. Security – protection of data from unauthorized access.

Properties of a Good Network

1. Interpersonal communication – email, chat, video calls.
2. Resource sharing – printers, scanners, etc.
3. File/data sharing – only authorized users.

Basic Communication Model

• Source → generates data.
• Transmitter → encodes data into signals.
• Transmission System → medium/channel carrying data.
• Receiver → decodes signals.
• Destination → final recipient.

Data Communication