Chapter 1 : Computer Networks. Lecture 1

Chapter 1 : Computer Networks.
Lecture 1
Introduction to computer networks:
Network definition :
A network is a collection of computers and other
devices that connected together in such way to share
resources (send data to and receive data) from each
other over a network media.
Introduction to computer networks:
Network definition :
A network can be defined also as two or more
computers connected together in such a way that
they can share resources.
Introduction to computer networks:
A resource may be:
- A file
- A folder
- A printer
- A disk drive
- Or just about anything else that exists on a computer.
Introduction to computer networks:
There are Three things needed to have a Network:
1-Hosts (PCs, laptops, peripheral devices)
2- A pathway to transfer data (Transmission media) i.e.
cables, air …etc.
3- Network Interface Card (NIC).
Basic concepts:
Devices :
- A term device is used to represent any entity that is
connected to a network.
- It includes printers, computers, servers, repeaters,
hubs, bridges, switches …. etc.
- Other name commonly used in networks for the
word Device is Node.
Basic concepts:
Local Devices :
- The device starting the communication across the
network is called Local device.
Goals of Computer Networks:
1- Resource Sharing:
Goal is to make the devices, programs and DATA
available to anyone on the network.
For Example: File, printer, File exchange, disk sharing.
Goals of Computer Networks:
2- High Reliability:
Goal is to provide high reliability by having alternate
source of supply.
For example: All files/ Data can be copied to 2-3
machines on the network so that if one machine fails
other can still provide the data.
Goals of Computer Networks:
3- Saving Money:
Network of devices and computers saves a lot of
For example: One printer can be shared with ten of
computers, so no need to buy separate printers for
each computer.
Goals of Computer Networks:
4- Communication Media:
It is the biggest source of communication media.
For example: Information can be shared within the
organization even if its offices are far apart. When one
worker makes changes to the on-line document,
others can see the changes immediately, thus making
the functionality of the organization very fast and
Advantages of Computer Networks:
- Connectivity and Communication.
- Data Sharing.
- Hardware Sharing .
- Internet Access .
- Performance Enhancement .
- Entertainment .
Disadvantages of Computer Networks:
Network Hardware, Software and Setup Costs.
Hardware and Software Management and
Administration Costs.
Undesirable Sharing.
Illegal or Undesirable Behavior.