UNIT 1: Introduction to Computer Networks
Computer Engineering Section
University Women’s Polytechnic
Aligarh Muslim University, Aligarh
February 22, 2020
Dr. J. Alam (CES) Unit 1: Introduction February 22, 2020 1 / 113
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Computer Networks: Types, Topologies, and Segmentation, Lecture notes of Computer Networks
An introduction to computer networks, discussing the concepts of network connections, categories of networks, network topologies, network configurations, expanding networks, network segmentation, and network performance parameters. It also covers special types of networks and network devices.
What you will learn
- What are the different categories of computer networks based on transmission technology and scale?
- What are some special types of computer networks and devices?
- What is network segmentation and why is it important?
- What is a computer network and how does it work?
- What are the advantages and disadvantages of different network topologies?
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UNIT 1: Introduction to Computer Networks
Computer Engineering Section
University Women’s Polytechnic
Aligarh Muslim University, Aligarh
February 22, 2020
Outline
Computer Networks: What and Why??
Applications of Computer Networks
Types of Network Connections
Categories of Networks: LAN, MAN & WAN
Network Topologies
Network Configurations: Server Based, Peer-to-Peer & Hybrid
Expanding Networks
Network Segmentation
Types of Servers
Network Performance Parameters: Bandwidth, Throughput,
Latency, Jitter etc.
Centralized Computing Vs. Networking I
In centralized computing there is a computer with single powerful CPU and a number of terminals are connected to it as shown in the figure on slide 6. All processing is performed within the boundaries of the same physical computer. User terminals are typically dumb ones, incapable of functioning on their own. They are cabled to the central computer. Sometimes these terminals have very little processing power and memory of their own and are called intelli- gent terminals.
Centralized Computing Vs. Networking II
This architecture places the tremendous burden on the central computer. In recent years, there have been significant advances in the development of high performance personal comput- ers and networks. There is now an identifiable trend in industry towards downsizing, i.e. replacing expensive mainframe com- puters with more cost effective networks of personal computers that achieve the same or even better results.
Why Networks??
Networks are all about:
Sharing Resources.
Preserving Information.
Protecting Information.
Sharing Resources I Resource sharing means sharing H/W and S/W. Hardware Resource Sharing: Networked Computers can share:
Printers, Fax Modem, Scanners, Hard Disks, Floppy Disks, CD-ROMS,
Tape Backup Units, Plotters, Any device that can be attached to the
Network.
Software Resource Sharing:
Software resources can be used more effectively over networks. With
stand alone computers the software used on the computers must be
present on each computer’s hard disk, whether or not that computer is
used at that moment for the task the software performs.
For a large number of stand alone computers S/W cost can become
more than expectations. It is also difficult and time consuming to install
and configure the S/W individually on each computer.
Preserving Information Besides, information and resource sharing a network al- lows information to be backed up to a central location. Important information can be lost by mistake or acci- dentally when a stand alone computer has no backup means. It is also difficult to maintain regular backups on a num- ber of stand alone computers. In a networked environment when we take backup at a central location from all computers, we have one place to preserve it.
Protecting Information With stand alone computer, access to the computer means access to the information on that computer. Networks provide an additional layer of security by means of passwords. We can give each network user a different account name and password, allowing the network server to distinguish among those who need access to have it and protecting the information from tampering by those who do not.
Components of a Data Communication System II (^4) Transmission Medium: The transmission medium is the physical path by which a message travels from sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves
Components of a Data Communication System III (^5) Protocol: A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating, just as a person speaking French cannot be understood by a person who speaks only Japanese.
Transmission Modes II
2 Half Duplex - both station can transmit and receive but not at
the same time, entire capacity of the channel can be used for
each direction. Example of half duplex is a walkie- talkie in which
message is sent one at a time and messages are sent in both the
directions.
Transmission Modes III
3 Full Duplex - both stations can transmit and receive simultane-
ously, either separate channels or channel can be divided between
signals traveling in both directions.
Example of Full Duplex is a Telephone Network in which there is
communication between two persons by a telephone line, through
which both can talk and listen at the same time.
Broadcast Networks I
1 Broadcast networks have a single communication channel that is
shared or used by all the machines on the network. Short messages
called packets sent by any machine are received by all the others.
2 Broadcast systems generally use a special code in the address field
for addressing a packet to all the concerned computers. This mode
of operation is called broadcasting.
3 Some broadcast systems also support transmission to a subset of
the machines known as multicasting.
4 Upon receiving a packet, a machine checks the address field. If the
packet is addressed to it then the packet is processed, otherwise
the packet is ignored.
5 The channel’s capacity is shared temporarily among the devices
connected to the link.
Broadcast Networks II