Summarize the following text to main points and sub-points and make detailed explain for them:

Communication 
Systems
By
Dr. Reham Abobeah
50 mark 
Midterm 
100 mark
Final Exam
150 mark
Text Book
Data and Computer Communications 
8th edition by William Stallings,
Prentice Hall, 2006
Download Link:
https://www.readallbooks.org/book/data-and-computer-communications-8th-edition/
Evaluation
Reference
History of computer Networks
Mainframes & Dumb terminals.
Disadvantages of these systems
• The financial cost of these systems is very high.
• Beneficiaries cannot fully utilize these systems.
• Potential single point of failure.
Mini-computers/single user 
➢Distributed computing or distributed processing.
Sneaker net
                          
                                The sneaker net
Sneaker Net Disadvantages
➢The need for a large amount of floppy disks or a set of CD-ROMs or 
DVDs.
➢A lot of effort and time are needed, and a high  probability of data transfer 
errors.
❑If you have one printer and several PCs, you must move the printer & 
connect to the intended PC, or leave the printer connected to one PC & wait 
for a long line to print.
A printer in a stand-alone environment
Due to the disadvantages of these separate individual 
devices, the best solution was to connect these PCs with 
each other through a master device that organizes operations 
between them.
OR, the simplest image of ​network using via connecting two 
computers together through a communication line to transfer 
data between them.
Sharing a printer in a networking environment
A simple computer network
These networks were characterized by:
1.
Each PC has a separate operation from the main server, 
[Distributed Processing System (DPS)]. 
2.
The sub-units in the network are called several names 
including: (client - end user - node - work station - agent - 
host).
3.
Networks can do many tasks, including: Store and retrieve 
files, sharing Resources, manage users, Security because 
each subnet has user name and password.
General definition of networks
A network is a set of electronic devices connected to each 
other for the purpose of sharing information and services.
 
Definition of computer networks
Computer Network is a communication system developed to 
connect a variety of different computers with  each other by 
means of connecting units (NIC), transmission media 
(Cables) and Network devices (Switches- Repeaters – 
Routers – Bridge-…).
COMPONENTS OF COMPUTER  NETWORK
➢Two or more computers (clients & servers PCs)
➢A network interfacing card(NIC) for each PC.
➢Software called operating system (OS)
➢Transmission Media (Cables) as links between the PCs 
(twisted pair, Coaxial, Fiber optics).
➢Peripherals or shared resources (Storage units, printers, Fax).
➢Network Devices for connecting the desired network (Hubs, 
Repeaters, Bridges, Switches).
❑FILE SHARING – Networks offer a quick and  
easy way to share files directly.
❑RESOURCE SHARING – All computers
in the 
network can share resources such as printers, fax 
machines, scanners, and modems.
❑COMMUNICATION –Those on the network can  
communicate with each other via e-mail,  
instant messages, etc.
❑Flexible Access -  Networks allow their users  to 
access files from computers throughout  the 
network.
❑Sharing of Information - Computer  networks 
enable us to share data and  information with the 
computers that are  located geographically large 
distance apart.
❖The different types of network are based on following:
❑Size of the network– Refers to the area over  which the 
network is spread.
❑Connection – Refers to the transmission media  and 
protocols used for connecting.
❑Network topology – Arrangement of computers  on the 
network.
ON  THE  BASIS  OF  SIZE
ON  THE  BASIS  OF  SIZE
1. LAN
A local area network (LAN) is a data communication system that allows a 
number of independent devices (PCs) to communicate with each other and 
share the network resources such as printer, fax, files storage devices, and 
application programs.
It is distinguished from other types of data networks in that the communication 
is usually confined to small/moderate-size geographical area such a single 
office, or LAB.
LAN runs at a speed of either 10 / 100 / 1000 Mbps, and has low delays.
A LAN based on wireless technology is called wireless local area  network
(WLAN).
LAN Characteristics:
✓Sharing Resources (Scanners, printers, application programs)
✓Allowing the communication between users(E-mail)
✓Short distance span: LAN connects computers in a small area 
like a  room, LAB, office, or a campus spread up  to a few 
meters.
✓Low error rate and high reliability.
✓Narrowly owned (usually a single private owner)
✓Ensuring the compatibility between different manufacture-
equipments.
2. METROPOLITAN
AREA  NETWORK  (MAN)
ON  THE  BASIS  OF  SIZE
MAN is a computer network which connects several 
LAN spread over a city.
This network is used to connect several offices in 
different building in closed area.
➢For example, faculty of Engineering consists of 
several departments, each department is in a 
building, and all buildings are in one place.
It covers the distance upto 30-50 km.
3.WIDE AREA  
NETWORK (WAN)
ON  THE  BASIS  OF  SIZE
WAN is a network that connects computers  over long distances 
like cities, countries,  continents or worldwide.
It allows users to have real-time communication capabilities with 
other users.
It is slower and less reliable than a LAN.
INTERNET is a common example of WAN.
Differentiate between the types of computer 
networks, LAN, MAN, and WAN?
LOCAL AREANETWORK
Types of LANs
CLIENT SERVERNETWORK
PEER TO PEER NETWORK
CLIENT
-SER
VER NETWORK
In client-server network, every PC performs only one job: client 
or server (but not both jobs)
✓A server is simply a  computer that contains all the network 
resources and is responsible for all client requests. 
✓A client is  a computer running a program that requests the 
service  from a server.
LAN is based on client-server network.
A client-server network , all available network  resources such as 
files, directories, applications and shared  devices, are centrally 
managed and hosted  by the server and then are  accessed by 
client.
In Client serve network, servers  provide security and 
administration to the  network.
TYPES OF SERVERS
File server: provides the services for  storing, retrieving and moving the data. 
✓A user can read, write, exchange and manage the files with the help of file 
servers.
Printer server: controls and manages printing on the network. It also offers 
the fax service to the network users.
Application server: The expensive software & additional  computing power 
can be shared by the computers in a  network with the help of application 
servers.
Database server: It is a type of application server. It allows  the users to 
access the centralized strong database.
Message server: It is used to co-ordinate the interaction  between users, 
documents and applications. The data can be  used in the form of audio, 
video, binary, text or graphics.
TY
 PES   OF S
E
R
V
E
R
S
P2P NETWORK
In p2p network, each computer can function as both client and server.
➢i.e. All PCs are equal in their importance in the network, thus PCs are called 
peers.
Network resources (scanner, printers, app programs) are distributed among 
PCs.
Each computer is responsible for making its own resources available to other 
computers on the network.
Each computer is responsible for setting up and maintaining its own security for 
these resources.
Each computer is responsible for accessing the required  network resources 
from peer to peer relationships.
It is useful for a small network containing less than 10 computers on a single 
LAN .
P2P networks do not have a central control system.
➢There are no servers in peer networks.
Pros.
✓In this network, no need to server or network administrator, 
but it is easy to set up and provide file sharing and printer 
sharing.
Cons.
o This network isn’t useful in security, backup, database apps, 
large networks.
P2P networks
Differentiate between peer to peer and client 
server networks?
Any Questions?


Summary :