u nit -1 basics of computer network · computer resources in a geographic area or region larger...
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UNIT-1
BASICS OF COMPUTER
NETWORK
SYLLABUS
1a.List the applications of Computer Network
1b.Differentiate Various Line configuration
1c. Design Computer Network considering
particular topology
1d.Categories Computer Network based on scope
and connection
1e.Explain use of various types of servers.
TOPICS AND SUB-TOPICS
1.1 Definition and history of networks
1.2 Usage of Computer Networks
1.3 Standard Organizations and protocol
1.4 Line Configurations
1.5 Network Topology
1.6 Categories of network based on topology and
based on connection
1.7 Applications and features of different types of
servers : File server ,Print server, Mail
server,Web server,Proxy server
1.1 COMPUTER NETWORKS
Computer network connects two or more autonomous computers.
Introdution to Computer Networks
APPLICATIONS OF NETWORKS
1.Resource Sharing
Hardware (computing resources, disks, printers)
Software (application software)
2.Information Sharing
Easy accessibility from anywhere (files, databases)
Search Capability (WWW)
3.Communication
Message broadcast
4.Remote computing
Introduction to Computer Networks
DATA COMMUNICATION SYSTEM COMPONENTS
1.2 USAGE OF COMPUTER NETWORKS
1.Resource Sharing:
2.High Reliability:
3.Saving Money:
4.Scalability:
5.Access to Remote Information:
6. Person to Person Communication:
7. Interactive Entertainment:
1.3 STANDARD ORGANIZATION AND
PROTOCOLS
1. ORGANIZATIONS FOR
COMMUNICATION STANDARDS
Standards are developed by cooperation among
standards creation committees, forums, and
government regulatory agencies.
Standards Creation Committees
a) International Standards Organization (ISO)
b) International Telecommunications Union (ITU)
c) American National Standards Institute (ANSI)
d) Institute of Electrical and Electronics Engineers (IEEE)
e) Electronic Industries Association (EIA)
f) Internet Engineering Task Force (IETF)
A) INTERNATIONAL STANDARDS
ORGANIZATION (ISO)
A multinational body whose membership is drawn mainly from the standards creation committees of various governments throughout the world
Dedicated to worldwide agreement on international standards in a variety field.
Currently includes 82 memberships industrialized nations.
Aims to facilitate the international exchange of goods and services by providing models for compatibility, improved quality, increased quality, increased productivity and decreased prices.
B) INTERNATIONAL
TELECOMMUNICATIONS UNION (ITU)
Also known as International Telecommunications Union-Telecommunication Standards Sector (ITU-T)
An international standards organization related to the United Nations that develops standards for telecommunications.
Two popular standards developed by ITU-T are:
i) V series – transmission over phone lines
ii) X series – transmission over public digital networks, email and directory services and ISDN.
C) AMERICAN NATIONAL STANDARDS
INSTITUTE (ANSI)
- A non-profit corporation not affiliated with
US government.
- ANSI members include professional
societies, industry associations,
governmental and regulatory bodies, and
consumer groups.
- Discussing the internetwork planning and
engineering, ISDN services, signaling, and
architecture and optical hierarchy.
D) INSTITUTE OF ELECTRICAL AND
ELECTRONICS ENGINEERS (IEEE)
The largest national professional group involved in
developing standards for computing, communication,
electrical engineering, and electronics.
Aims to advance theory, creativity and product quality
in the fields of electrical engineering, electronics and
radio.
It sponsored an important standard for local area
networks called Project 802 (eg. 802.3, 802.4 and 802.5
standards.)
E) ELECTRONIC INDUSTRIES
ASSOCIATION (EIA)
An association of electronics manufacturers in the US.
Provide activities include public awareness education
and lobbying efforts in addition to standards
development.
Responsible for developing the EIA-232-D and EIA-530
standards.
F) INTERNET ENGINEERING TASK FORCE
(IETF)
Concerned with speeding the growth and
evolution of Internet communications.
The standards body for the Internet itself
Reviews internet software and hardware.
1.4 LINE CONFIGURATION
Point-to-Point Line Configuration
Point-to-Point Line Configuration
Point-to-Point Line Configuration
Multipoint Line Configuration
1.5 NETWORK TOPOLOGY
TOPOLOGY
Topology refers to the layout of connected
devices on a network.
Here, some logical layout of topology.
1. Mesh
2. Star
3. Bus
4. Ring
5. Tree and Hybrid
NETWORK TOPOLOGY
MESH TOPOLOGY
Here every device has a point to point link to
every other device.
Node 1 node must be connected with n-1
nodes.
A fully connected mesh can have n(n-1)/2
physical channels to link n devices.
It must have n-1 I/O ports.
MESH TOPOLOGY
Advantages:
1. They use dedicated links so each link
can only carry its own data load. So
traffic problem can be avoided.
2. It is robust. If any one link get damaged
it cannot affect others.
3. It gives privacy and security.(Message
travels along a dedicated link)
4. Fault identification and fault isolation
are easy.
MESH TOPOLOGY
MESH TOPOLOGY
MESH TOPOLOGY
Disadvantages:
1. The amount of cabling and the number of
I/O ports required are very large. Since
every device is connected to each devices
through dedicated links.
2. The sheer bulk of wiring is larger then the
available space.
3. Hardware required to connected each
device is highly expensive.
MESH TOPOLOGY
Applications:
1. Telephone Regional office.
2. WAN.(Wide Area Network).
STAR TOPOLOGY
1. Here each device has a dedicated point-to-
point link to the central controller called
“Hub”(Act as a Exchange). 2. There is no direct traffic between devices.
3. The transmission are occurred only
through the central “hub”. 4. When device 1 wants to send data to
device 2; First sends the data to hub.
Which then relays the data to the other
connected device.
STAR TOPOLOGY
STAR TOPOLOGY
STAR TOPOLOGY
Advantages:
1. Less expensive then mesh since each
device is connected only to the hub.
2. Installation and configuration are easy.
3. Less cabling is need then mesh.
4. Robustness.(if one link fails, only that
links is affected. All other links remain
active)
5. Easy to fault identification & to remove
parts.
6. No distruptions to the network then
connecting(or) removing devices.
STAR TOPOLOGY
Disadvantages:
1. Even it requires less cabling then mesh
when compared with other topologies it
still large.(Ring or bus).
2. Dependency(whole n/w dependent on one
single point(hub). When it goes down. The
whole system is dead.
APPLICATIONS
Star topology used in Local Area
Networks(LANs).
High speed LAN often used STAR.
BUS TOPOLOGY
A bus topology is multipoint.
Here one long cable act as a backbone to link
all the devices are connected to the backbone
by drop lines and taps.
Drop line- is the connection b/w the devices
and the cable.
Tap- is the splitter that cut the main link.
This allows only one device to transmit at a
time.
BUS TOPOLOGY
BUS TOPOLOGY
BUS TOPOLOGY
BUS TOPOLOGY
BUS TOPOLOGY
A device want to communicate with other
device on the n/ws sends a broadcast message
onto the wire all other devices see.
But only the intended devices accepts and
process the message.
BUS TOPOLOGY
Advantages:
1. Ease of installation
2. Less cabling
Disadvantages:
1. Difficult reconfiguration and fault
isolation.
2. Difficult to add new devices.
3. Signal reflection at top can degradation in
quality.
4. If any fault in backbone can stops all
transmission.
BUS TOPOLOGY
Applications:
Most computer motherboard.
RING TOPOLOGY
Here each device has a dedicated connection
with two devices on either side.
The signal is passed in one direction from
device to device until it reaches the
destination and each device have repeater.
When one device received signals instead of
intended another device, its repeater then
regenerates the data and passes them along.
To add or delete a device requires changing
only two connections.
RING TOPOLOGY
RING TOPOLOGY
RING TOPOLOGY
RING TOPOLOGY
Advantages:
Easy to install.
Easy to reconfigure.
Fault identification is easy.
Disadvantages:
Unidirectional traffic.
Break in a single ring can break entire
network.
RING TOPOLOGY
Applications:
Ring topologies are found in some office
buildings or school campuses.
Today high speed LANs made this topology
less popular.
TREE TOPOLOGY
Alternatively referred to as a star bus
topology.
Tree topology is one of the most common
network setups that is similar to a bus
topology and a star topology.
A tree topology connects multiple star
networks to other star networks. Below is a
visual example of a simple computer setup on
a network using the star topology.
TREE TOPOLOGY
HYBRID TOPOLOGY
A network which contain all type of physical
structure and connected under a single
backbone channel.
HYBRID TOPOLOGY
a
CONSIDERATIONS FOR CHOOSING
TOPOLOGY
Money-Bus n/w may be the least expensive way to
install a n/w.
Length-of cable needed- the linear bus n/w uses
shorter lengths of cable.
Future growth-with star topology, expending a n/w is
easily done by adding another devices.
Cable type-most common used cable in commercial
organization is twisted pair. Which often
used with star topologies.
CONTINUE…
Full mesh topology is theoretically the best
since every device is connected to every
other device.(thus maximizing speed and
security. however, it quite expensive to
install)
Next best would be tree topology, which is
basically a connection of star.
1.6 CATEGORIES OF NETWORK
Based on scope
Based on Connection
1.6 TYPES OF NETWORK:
Local Area Network
Wide Area Network
Metropolitan Area Network
57
LOCAL AREA NETWORK:
A local area network (LAN) is a group of
computers and associated devices that share a
common communications line or wireless link.
Typically, connected devices share the resources
of a single processor or server within a small
geographic area .
A local area network may serve as few as two or
three users or as many as thousands of users.
58
59
WIDE AREA NETWORK:
The WAN is a communications network that
makes use of existing technology to connect
local computer networks into a larger
working network that may cover both
national and international locations.
60
61
METROPOLITAN AREA NETWORK
(MAN):
A metropolitan area network (MAN) is a
network that interconnects users with
computer resources in a geographic area or
region larger than that covered by even a
large local area network but smaller than the
area covered by a wide area network (WAN).
It is also used to mean the interconnection of
several local area networks by bridging them
with backbone lines
62
NETWORK TOPOLOGIES
Network Topology – Maps of how the
physical or logical paths of network
devices connect. The three major
topologies are star, ring, and bus.
Star Topology – Most common Ethernet
network topology where each device
connects to a central hub or switch.
Hub – A device used with the Universal
Serial Bus or in a star network topology
that allows multiple device connections.
Switch – In star networks, a Layer 2 central
controlling device.
63
NETWORK TOPOLOGIES
64
HUB/SWITCH
NETWORK TOPOLOGIES
65
STAR TOPOLOGY
NETWORK TOPOLOGIES
66
LOGICAL RING TOPOLOGY
NETWORK TOPOLOGIES
67
Bus Topology
NETWORK TOPOLOGIES
68
DIFFERENTIATE BETWEEN THE THREE
TYPES OF COMPUTER NETWORKS
SIMPLEX
HALF-DUPLEX
FULL-DUPLEX
1.6 CATEGORIES OF NETWORK
BASED ON SCOPE
BASED ON CONNECTION
LAN, MAN & WAN
Network in small geographical Area (Room, Building or a Campus) is called LAN (Local Area Network)
Network in a City is call MAN (Metropolitan Area Network)
Network spread geographically (Country or across Globe) is called WAN (Wide Area Network)
LOCAL AREA NETWORK
LOCAL AREA NETWORK
METROPOLITAN AREA NETWORK
WIDE AREA NETWORK
Figure 2-19
WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998
INTERNETWORK
(INTERNET)
NETWORK TOPOLOGY
The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.
Introduction to Comuter Networks
MESH TOPOLOGY The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance.
It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions.
Implementing the mesh topology is expensive and difficult.
Introduction to Computer Networks
MESH TOPOLOGY
MERITS
NO CONGESTION
PROBLEM
NO MAC PROTOCOLS
ARE NEEDED
MORE SECURE
IT IS ROBUST
FAULT IDENTIFICATION
IS EASY
DEMERITS
CABLE LENGTH
IMPRACTICAL FOR
LARGE NETWORKS
STAR & TREE TOPOLOGY
THE STAR TOPOLOGY IS THE MOST COMMONLY USED ARCHITECTURE IN ETHERNET LANS.
WHEN INSTALLED, THE STAR TOPOLOGY RESEMBLES SPOKES IN A BICYCLE WHEEL.
LARGER NETWORKS USE THE EXTENDED STAR TOPOLOGY ALSO CALLED TREE TOPOLOGY. WHEN USED WITH NETWORK DEVICES THAT FILTER FRAMES OR PACKETS, LIKE BRIDGES, SWITCHES, AND ROUTERS, THIS TOPOLOGY SIGNIFICANTLY REDUCES THE TRAFFIC ON THE WIRES BY SENDING PACKETS ONLY TO THE WIRES OF THE DESTINATION HOST.
Itroduction to Computer Networks
STAR & TREE TOPOLOGY
MERITS
CHEAPER THAN MESH TOPOLOGY
RELATIVELY EASIER TO INSTALL, MAINTAIN &
CONFIGURE
DEMERITS
IF HUB GOES DOWN THE ENTIRE NETWORK
BECOMES DEFUNCT
RING TOPOLOGY
A FRAME TRAVELS AROUND THE RING, STOPPING AT EACH NODE. IF A NODE WANTS TO TRANSMIT DATA, IT ADDS THE DATA AS WELL AS THE DESTINATION ADDRESS TO THE FRAME.
THE FRAME THEN CONTINUES AROUND THE RING UNTIL IT FINDS THE DESTINATION NODE, WHICH TAKES THE DATA OUT OF THE FRAME.
Introduction to Computer Networks
RING TOPOLOGY
MERITS
EASY TO RECONFIGURE AND INSTALL.
FAULT ISOLATION IS RELATIVELY EASY IN A
RING.
DEMERITS
IF A NODE IN A SIMPLE RING FAILS, THE WHOLE
RING CAN NOT FUNCTION.
BUS TOPOLOGY
COMMONLY REFERRED TO AS A LINEAR BUS, ALL THE DEVICES ON A BUS TOPOLOGY ARE CONNECTED BY ONE SINGLE CABLE.
BUS TOPOLOGY
MERITS
EASY TO INSTALL
USES LESS CABLE
DEMERITS
RELATIVELY DIFFICULT
TO ADD NEW NODES.
EVEN IF A PORTION OF
THE BUS BREAKS DOWN,
THE WHOLE BUS CAN NOT
FUNCTION.
1.7 FILE SERVER
IN COMPUTING, A FILE SERVER (OR FILESERVER)
IS A COMPUTER ATTACHED TO A NETWORK THAT
HAS THE PRIMARY PURPOSE OF PROVIDING A
LOCATION FOR SHARED DISK ACCESS, I.E.
SHARED STORAGE OF COMPUTER FILES (SUCH AS
DOCUMENTS, SOUND FILES, PHOTOGRAPHS,
MOVIES, IMAGES, DATABASES, ETC.)
IN COMPUTING, A FILE SERVER (OR FILESERVER)
IS A COMPUTER ATTACHED TO A NETWORK THAT
HAS THE PRIMARY PURPOSE OF PROVIDING A
LOCATION FOR SHARED DISK ACCESS, I.E.
SHARED STORAGE OF COMPUTER FILES (SUCH AS
DOCUMENTS, SOUND FILES, PHOTOGRAPHS,
MOVIES, IMAGES, DATABASES, ETC.)
PRINT SERVER
A PRINT SERVER, OR PRINTER SERVER, IS A
DEVICE THAT CONNECTS PRINTERS TO CLIENT
COMPUTERS OVER A NETWORK.
PROXY SERVER
A PROXY SERVER IS A COMPUTER THAT OFFERS
A COMPUTER NETWORK SERVICE TO ALLOW
CLIENTS TO MAKE INDIRECT NETWORK
CONNECTIONS TO OTHER NETWORK SERVICES
WEB SERVER
A WEB SERVER IS AN INFORMATION
TECHNOLOGY THAT PROCESSES REQUESTS VIA
HTTP, THE BASIC NETWORK PROTOCOL USED
TO DISTRIBUTE INFORMATION ON THE WORLD
WIDE WEB.
APPLICATION SERVER
AN APPLICATION SERVER IS A COMPONENT-
BASED PRODUCT THAT RESIDES IN THE MIDDLE-
TIER OF A SERVER CENTRIC ARCHITECTURE.
MAIL SERVER
A MAIL SERVER (ALSO KNOWN AS A MAIL
TRANSFER AGENT OR MTA, A MAIL TRANSPORT
AGENT, A MAIL ROUTER OR AN INTERNET
MAILER) IS AN APPLICATION THAT RECEIVES
INCOMING E-MAIL FROM LOCAL USERS (PEOPLE
WITHIN THE SAME DOMAIN) AND REMOTE
SENDERS AND FORWARDS OUTGOING E-MAIL FOR
DELIVERY.