Introduction to Networks Lecture 1
Dr John C. Murray Principal Lecturer
What is a Network?
• “a large system consisting of many similar parts connected together to allow movement or communication between or along the parts”
• noun
– 1. an arrangement of intersecting horizontal and vertical lines:
• a spider constructs a complex network of several different kinds of threads
– 2. a group or system of interconnected people or things:
• the company has a network of 326 branches
Communication Networks
• What was one of the first communication networks?
– Postal Service
– Telephone Network
• Interesting fact – before telephone networks, phones were connected point to point
• People needed a telephone for each person they wanted to speak to
• They would whistle until the other person answered
– Then telephone exchanges were born
PSTN
• Public Switched Telephone Network
Computer Network
• A collection of? – Computers
– Switches
– Routers
– Bridges
– Cables
– Wifi Routers / Access Points – Anything else?
Communication
• Purpose of a computer network is to
communicate information from point A B – Efficiently…
– Quickly…
– Reliably…
• However, there are many ways in which a Computer Network can be configured.
– Which we will look at in a bit
A Computer Network
• The Internet is one of the more common computer networks we know of today
– This is very different from the World Wide Web (WWW) more on this later…
– How old is the internet?
– Maybe older than you think • Started in the 1960’s
• ARPAnet
ARPAnet
• Advanced Research Projects Agency Network
– Worlds first packet switching network (more on this later)
– First network to use TCP/IP
– Created as an experiment by US military
– To test communications in a nuclear strike
– Later used to connect universities and researchers
• And grew exponentially
Connected Devices
Connected Devices
Circuit Switching
• Establishes a point to point connection between two devices
– Channel is dedicated
– Full bandwidth given
– Remains connected for duration of communication
• Minimal delays
– Channel is dedicated
• Highly inefficient
Questions