Computer Networks

WHAT IS COMPUTER NETWORK?
• A set of devices often mentioned as nodes connected by media link is
called a Network. A node can be a device which is capable of sending
or receiving data generated by other nodes on the network like a
computer, printer etc.
• A network must be able to meet certain criteria, these are mentioned
below:
 Performance
 Reliability
 Scalability
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Basic Communication Model
• A Communication model is used to exchange data between two
parties.
• For example: communication between a computer, server and
telephone (through modem).
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Line Configuration in Computer
Networks
• A Network is nothing but a connection made through connection
links between two or more devices. Devices can be a computer,
printer or any other device that is capable to send and receive data.
There are two ways to connect the devices:
 Point-to-Point connection
 Multipoint connection
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Point-To-Point Connection
• It is a protocol which is used as a communication link between two
devices.
• It is simple to establish.
• The most common example for Point-to-Point connection (PPP) is a
computer connected by telephone line.
• We can connect the two devices by means of a pair of wires or using a
microwave or satellite link.
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MultiPoint Connection
• There are two kinds of Multipoint Connections :
 If the links are used simultaneously between many devices, then it is
spatially shared line configuration.
 If user takes turns while using the link, then it is time `shared (temporal)
line configuration
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BUS Topology
• Bus topology is a network type in which every computer and network
device is connected to single cable.
• When it has exactly two endpoints, then it is called Linear Bus
topology
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Features of Bus Topology
• It transmits data only in one direction.
• Every device is connected to a single cable

Advantages of Bus Topology
• It is cost effective.
• Cable required is least compared to other network topology.
• Used in small networks.
• It is easy to understand.
• Easy to expand joining two cables together.
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Disadvantages of Bus Topology
• Cables fails then whole network fails.
• If network traffic is heavy or nodes are more the performance of the
network decreases.
• Cable has a limited length.
• It is slower than the ring topology
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RING Topology
• It is called ring topology because it forms a ring as each computer is
connected to another computer, with the last one connected to the
first. Exactly two neighbors for each device.
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Features of Ring Topology
• A number of repeaters are used for Ring topology with large number of
nodes, because if someone wants to send some data to the last node in
the ring topology with 100 nodes, then the data will have to pass
through 99 nodes to reach the 100th node. Hence to prevent data loss
repeaters are used in the network.
• The transmission is unidirectional, but it can be made bidirectional by
having 2 connections between each Network Node, it is called Dual
Ring Topology.
• In Dual Ring Topology, two ring networks are formed, and data flow is
in opposite direction in them. Also, if one ring fails, the second ring can
act as a backup, to keep the network up.
• Data is transferred in a sequential manner that is bit by bit. Data
transmitted, has to pass through each node of the network, till the
destination node.
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Advantages and Disadvantages
• Advantages of Ring Topology
• Transmitting network is not affected by high traffic or by adding
more nodes, as only the nodes having tokens can transmit data.
• Cheap to install and expand
• Disadvantages of Ring Topology
• Troubleshooting is difficult in ring topology.
• Adding or deleting the computers disturbs the network activity.
• Failure of one computer disturbs the whole network
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STAR Topology
• In this type of topology all the
computers are connected to a single
hub through a cable. This hub is the
central node and all others nodes are
connected to the central node.
• Features of Star Topology
 Every node has its own dedicated
connection to the hub.
 Hub acts as a repeater for data flow.
 Can be used with twisted pair, Optical
Fibre or coaxial cable.
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Advantages and Drawbacks
Advantages of Star Topology
 Fast performance with few nodes and low network traffic.
 Hub can be upgraded easily.
 Easy to troubleshoot.
 Easy to setup and modify.
 Only that node is affected which has failed, rest of the nodes can work
smoothly.
Disadvantages of Star Topology
 Cost of installation is high.
 Expensive to use.
 If the hub fails then the whole network is stopped because all the nodes
depend on the hub.
 Performance is based on the hub that is it depends on its capacity
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MESH Topology
• It is a point-to-point connection to other nodes or devices. All the
network nodes are connected to each other. Mesh has n(n-
1)/2 physical channels to link n devices.
• Advantages of Mesh Topology
 Each connection can carry its own data load.
 It is robust.
 Fault is diagnosed easily.
 Provides security and privacy.
• Disadvantages of Mesh Topology
 Installation and configuration is difficult.
 Cabling cost is more.
 Bulk wiring is required.
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TREE Topology
• It has a root node and all other nodes are connected to it forming a
hierarchy. It is also called hierarchical topology. It should at least
have three levels to the hierarchy.
• Features of Tree Topology
 Ideal if workstations are located in groups.
 Used in Wide Area Network.
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Advantages & Drawbacks
Advantages of Tree Topology
 Extension of bus and star topologies.
 Expansion of nodes is possible and easy.
 Easily managed and maintained.
 Error detection is easily done.
Disadvantages of Tree Topology
 Heavily cabled.
 Costly.
 If more nodes are added maintenance is difficult.
 Central hub fails, network fails.
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HYBRID Topology
• It is two different types of topologies,
which is a mixture of two or more
topologies.
• For example if in an office in one
department ring topology is used and
in another star topology is used,
connecting these topologies will result
in Hybrid Topology (ring topology and
star topology).
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Advantage and Disadvantage
Advantages of Hybrid Topology
 Reliable as Error detecting and trouble shooting is easy.
 Effective.
 Scalable as size can be increased easily.
 Flexible.
Disadvantages of Hybrid Topology
 Complex in design.
 Costly.
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Transmission Modes in
Computer Networks
• Transmission mode refers to the
mechanism of transferring of
data between two devices
connected over a network.
• It is also called Communication
Mode.
• These modes direct the direction
of flow of information. There are
three types of transmission
modes. They are:
 Simplex Mode
 Half duplex Mode
 Full duplex Mode
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Simplex Mode
• In this type of transmission mode, data can be sent only in one
direction i.e. communication is unidirectional. We cannot send a
message back to the sender.
• Examples of simplex Mode are loudspeakers, television broadcasting,
television and remote, keyboard and monitor etc.
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HALF DUPLEX Mode
• Half-duplex data transmission means that data can be transmitted
in both directions on a signal carrier, but not at the same time.
• Example of half duplex is a walkie- talkie in which message is sent
one at a time but messages are sent in both the directions.
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FULL DUPLEX Mode
• In full duplex system we can send data in both the directions as it is
bidirectional at the same time in other words, data can be sent in
both directions simultaneously
• Example of Full Duplex is a Telephone Network in which there is
communication between two persons by a telephone line, using which
both can talk and listen at the same time.
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Transmission Mediums in Computer
Networks
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Factors to be considered while
selecting a Transmission Medium
• Transmission Rate
• Cost and Ease of Installation
• Resistance to Environmental Conditions
• Distances
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Types of Communication Networks
Types of Communication
Networks
1. Local Area Network (LAN)
2. Metropolitan Area Network
(MAN)
3. Wide Area Network (WAN)
4. Wireless
5. Inter Network (Internet)
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Synchronous, Asynchronous,
Isochronous. What does it mean?
• These are all methods used to transfer streams of data
• In Synchronous Transmission, data flows in a full duplex mode in the
form of blocks or frames. Synchronization between the sender and
receiver is necessary so that the sender know where the new byte starts
(since there is no gap between the data).
• Synchronous Transmission is efficient, reliable and is used for
transferring a large amount of data. It provides real-time
communication between connected devices
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Asynchronous Transmission
• In Asynchronous Transmission data flows in a half-duplex mode, 1
byte or a character at a time. It transmits the data in a continuous
stream of bytes. In general, the size of a character sent is 8 bits to
which a parity bit is added i.e. a start and a stop bit that gives the
total of 10 bits.
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Asynchronous
• It is simple, fast, economical and does not require a 2-way
communication. Letters, emails, forums, televisions and radios are
some of the examples of Asynchronous Transmission.
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Isochronous
• An isochronous data transfer system combines the features of an
asynchronous and synchronous data transfer system.
• An isochronous data transfer system sends blocks of data
asynchronously, in other words the data stream can be transferred at
random intervals.
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Key Differences Between Synchronous
and Asynchronous Transmission
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Synchronus Asynchronous
Data is transferred in the form of frames Data is transmitted 1 byte at a time
requires a clock signal between the
sender and receiver
Transmission sender and receiver does
not require a clock signal
High data transfer rate Slow data transfer rate
Complex, Expensive Simple and ecomomical
Efficient and lower overhead Overheads are more

Baseband vs Broadband
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BASIS FOR COMPARISON
BASEBAND
TRANSMISSION
BROADBAND
TRANSMISSION
Type of signaling used Digital Analog
Application Work well with bus
topology.
Used with a bus as well as
tree topology.
Encoding Used Manchester and
Differential Manchester
encoding.
PSK encoding.
Transmission Bidirectional Unidirectional
Signal range Signals can be travelled
over short distances
Signals can be travelled
over long distances without
being attenuated.

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Key Differences Between Baseband and Broadband Transmission
1. Baseband transmission utilizes digital signalling while broadband transmission uses
analog signalling.
2. Bus and tree topologies, both work well with the broadband transmission. On the
other hand, for the baseband transmission bus topology is suitable.
3. Baseband involves Manchester and differential manchester encoding. In contrast,
broadband does not make use of any digital encoding instead it uses PSK (Phase shift
keying) encoding.
4. The signals can be travelled in both the direction in baseband transmission whereas
in broadband transmission the signals can travel in only one direction.
5. In baseband transmission, the signals cover shorter distances because at higher
frequencies the attenuation is most pronounced which make a signal to travel short
distances without reducing its power. As against, in broadband signals, the signals
can be travelled at longer distances

Internet
• The Internet is generally defined as a
lobal network connecting millions of computers. More
than 190 countries are linked into exchanges of data,
news and opinions.
Is Web and Internet the Same?
 The Internet is not synonymous with World Wide Web.
 The Internet is a massive network of networks, a networking
infrastructure. It connects millions of computers together globally,
forming a network in which any computer can communicate with
each other.
 The World Wide Web, or simply Web, is a way of accessing
information over the medium of the Internet. It is an information-
sharing model that is built on top of the Internet.
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Who Owns the Internet?
• No one actually owns the Internet, and no single person
or organization controls the Internet in its entirety.
• The Internet is more of a concept than an actual tangible
entity, and it relies on a physical infrastructure that
connects networks to other networks.
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Connecting to the
Internet
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Dial up
• This is generally the slowest type of Internet connection,
• Try to avoid it unless it is the only service available in your area.
• Dial-up Internet uses your phone line,
• Unless you have multiple phone lines you will not be able to use your
landline and the Internet at the same time.
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DSL
• DSL service uses a broadband connection, which makes it much
faster than dial-up.
• DSL connects to the Internet via a phone line but does not require
you to have a landline at home.
• And unlike dial-up, you'll be able to use the Internet and your phone
line at the same time.
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Cable
• Cable service connects to the Internet via cable TV, although you do
not necessarily need to have cable TV in order to get it.
• It uses a broadband connection and can be faster than both dial-up
and DSL service;
• however, it is only available where cable TV is available
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Satellite
• A satellite connection uses broadband but does not require cable or
phone lines;
• It connects to the Internet through satellites orbiting the Earth.
• As a result, it can be used almost anywhere in the world, but the
connection may be affected by weather patterns.
• Satellite connections are also usually slower than DSL or cable.
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3G and 4G
• 3G and 4G service is most commonly used with mobile phones, and it
connects wirelessly through your ISP's network.
• However, these types of connections aren't always as fast as DSL or
cable.
• They will also limit the amount of data you can use each month,
which isn't the case with most broadband plans.
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Connect to the Internet using a
smartphone
• You may also be able to use your smartphone as an Internet
connection for your computer.
• Doing so requires you to use tethering software, which allows the
smartphone to act as a modem or wireless access point for the
computer to use for Internet access.
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Choosing an Internet service provider
• You have idea about different types of Internet connectivity
• Make the search for the available ISP in your area
• We may suggest to take opinion from your friends and neighbors about
the ISP that they are using
• Most of the ISP’s offering different tier of services with different speeds
in Mbps
• If you are interested to use Internet for email and social networking,
a slower connection (around 2 to 5 Mbps) might be all you need.
• if you want to download music or stream videos, you'll want a faster
connection (at least 5 Mbps or higher).
• You'll also want to consider the cost of the service, including
installation charges and monthly fees.
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URL Processing
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What is Internet ?
• Internet is worldwide collection of computer network
• It provides access to communication services and access to
information resources to the millions of users around the globe
• Internet covers globe and include large international network as well
as many smaller local area networks owned by any individual
company or country
• M/C or computer on one network can communicate with M/C or
computer on other network and send data file and other information
back and forth, for this work M/C on network must have to agree to
speak same language
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Evolution of Internet:
• 1960 US Department of defence started packet switched network
ARPANET (Advanced Research Project Agency)
• WAN now known as DARPA (Defence Advanced Research Project
Agency)
• Idea was to connect different geographical areas network and allow
the transmission in the form of packets
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Challenges faced by ARPA
• Interconnectivity: It deals with transportation of information and
for this software protocol is needed that could package and route the
information between multiple site and
 For this internet protocol is evolved ie TCP/IP
• Interpretability deals with application-to-application
communication, its challengeous because applications are running
vastly on different hardware platform with different operating
system & different file systems.
• Solution for this is to develop standard application protocol that
would enable application to application communication and be
independent of computer platform e.g. mainframe based email
program and PC based email program both are using same standard
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Tim Berners Lee WWW Creator
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What is WWW
• The World Wide Web (WWW) is combination of all resources and
users on the Internet that are using the Hypertext Transfer Protocol
(HTTP)
• "The World Wide Web is the universe of network-accessible
information
• Sir Tim Berners-Lee invented the World Wide Web in 1989.
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Evolution of WWW
• WWW is huge collection of hypertext pages on the Internet
• The first text-based prototype was opeConcept WWW is developed in
Switzerland by European laboratory for particle physics (known
CERN) in the year 1989
• rational in 1991, in the month of December 1991
• Tim Berners-Lee is the inventor of the Web and the director of the
W3C
• Berners-Lee developed hypertext, the method of instant cross-
referencing that supports communications on the Web, making it
easy to link content on one web page to content located elsewhere
• The World Wide Web has been widely available since 1991
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Difference between Internet & WWW
• Many people use the terms Internet and World Wide Web (aka. the
Web) interchangeably
• The Internet and the Web are two separate but related things
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Internet
• The internet is a massive network of networks, a networking
infrastructure.
 It connects millions of computers together globally
 It is a global network connecting millions of computers.
 The internet is decentralized.
 Each internet computer is independent.
 There are a variety of ways to access the internet.
 There are more than 3.5 billion internet users in the world
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WWW
• The World Wide Web, or simply web, is a way of accessing
information over the medium of the internet.
• It is an information-sharing model that is built on top of the internet.
• The web uses the HTTP protocol, only one of the languages spoken over
the internet, to transmit data.
• It is an information-sharing model that is built on top of the internet.
• The web uses the HTTP protocol, only one of the languages spoken over
the internet, to transmit data.
 Support specially formatted documents.
 Documents are formatted in a markup language that supports links to other
documents.
 You can jump from one document to another simply by clicking on hot spots
(hyperlinks).
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Webserver
• A Web server is a program that uses HTTP (Hypertext Transfer
Protocol)
• Serve the files that form Web pages to users, in response to their
requests, which are forwarded by their computers' HTTP clients.
• Dedicated computers and appliances may be referred to as Web
servers as well.
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What is Web Browser
• A web browser (commonly referred to as a browser) is a software
application for accessing information on the World Wide Web.
• Each individual web page, image, and video is identified by a
distinct URL, enabling browsers to retrieve and display them on
the user's device.
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Protocols, Building Web Sites
• The Internet relies on a number of protocols in order to function
properly.
• A protocol is simply a standard for enabling the connection,
communication, and data transfer between two places on a network.
• Here are some of the key protocols that are used for transferring
data across the Internet.
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HTTP
• HTTP stands for Hypertext Transfer Protocol.
• It is the standard protocol for transferring web pages (and their
content) across the Internet
• For browsing website url may preceded by http://
• It is telling browser to use HTTP to transfer data
• Most browser will default to HTTP if you don’t specify it e.g.
www.bitdurg.ac.in instead ( http://www.bitdurg.ac.in)
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HTTPS
• HTTPS stands for Hypertext Transfer Protocol over Secure Socket
Layer.
• Think of it as a secure version of HTTP.
• HTTPS is used primarily on web pages that ask you to provide
personal or sensitive information (such as a password or your credit
card details).
• When you browse a web page using HTTPS, you are using SSL
(Secure Sockets Layer).
• For a website to use HTTPS it needs to have an SSL
certificate installed on the server.
• These are usually issued by a trusted 3rd party, referred to as a
Certificate Authority (CA).
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FTP
• FTP stands for File Transfer Protocol. It is used to transfer files
across the Internet.
• FTP is commonly used by web developers to publish updates to a
website (i.e. to upload a new version of the website).
• HTTP is used for displaying the file in your browser, FTP is used
simply to transfer the file from one computer to a specified location
on another computer
• You can use FTP to transfer the files from your computer to a remote
computer (such as a web server), or to transfer from the remote
computer to your local computer.
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E-mail System
• E-mail system comprises of the following three components:
• Mailer
• Mail Server
• Mailbox
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Mailer
• It is also called mail program, mail application or mail client. It
allows us to manage, read and compose e-mail.
Mail Server
• The function of mail server is to receive, store and deliver the email. It is
must for mail servers to be sunning all the time because if it crashes or
is down, email can be lost.
Mailboxes
• Mailbox is generally a folder that contains emails and information about
them.
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Working of E-mail
Email working follows the client server approach. In this client is the
mailer i.e. the mail application or mail program and server is a device
that manages emails.
• Following example will take you through the basic steps
• Suppose person A wants to send an email message to person B.
• Person A composes the messages using a mailer program i.e. mail
client and then select Send option.
• The message is routed to Simple Mail Transfer Protocol to person
B’s mail server.
• The mail server stores the email message on disk in an area
designated for person B.
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• Now, suppose person B is running a POP client and knows how to
communicate with B’s mail server.
• It will periodically poll the POP server to check if any new email has
arrived for B.
• As in this case, person A has sent an email for person B, so email is
forwarded over the network to B’s PC.
• This is message is now stored on person B’s PC
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First Scenario
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1
2
When the sender and the receiver of an e-mail are on the same mail server,
we need only two user agents.

Second Scenario
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2 3 4
5
When the sender and the receiver of an e-mail are on different mail servers,
we need two UAs and a pair of MTAs (client and server).

Third Scenario
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When the sender is connected to the mail server via a LAN or a WAN, we
need two UAs and two pairs of MTAs
(client and server).

4th Scenario
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Mishra
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When both sender and receiver are connected to the mail server via a LAN or a WAN, we need two
UAs, two pairs of MTAs (client and server), and a pair of MAAs (client and server). This is the most
common situation today.

Push versus pull
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Set Up Your Gmail Account to
Use IMAP
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Allow Less Secure Apps to Access
Your Gmail Account
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Add Your Gmail Account to Outlook
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On the Account Information screen,
click Add Account
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Add Account dialog box, you can
choose the E-mail Account
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The progress of the setup displays.
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Choose Service screen, select POP or
IMAP and click Next.
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Enter your full email address for the
User Name
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E-mail Settings dialog box, click the
Outgoing Server tab.
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E-mail Settings dialog box, click the
Advanced tab.
Enter the following information:
 Incoming server: 993
 Incoming server encrypted connection: SSL
 Outgoing server encrypted connection TLS
 Outgoing server: 587
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Outlook tests the accounts settings by logging into the incoming mail server and sending a test email
message. When the test is finished, click Close.

OSI
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OSI Reference Model
• OSI Reference Model - internationally standardised network
architecture.
• OSI = Open Systems Interconnection: deals with open systems, i.e.
systems open for communications with other systems.
• Specified in ISO 7498.
• Model has 7 layers.
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7-layer OSI Reference Model
• Layers 1-4 relate to
communications
technology.
• Layers 5-7 relate to user
applications.
Layer 7
Layer 6
Layer 5
Layer 4
Layer 3
Layer 2
Layer 1
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Communications subnet boundary
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Layer – 7 Application Layer
• Level at which applications access network
services.
 Represents services that directly support software
applications for file transfers, database access, and
electronic mail etc.
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Layer 6: Presentation Layer
• Related to representation of transmitted data
 Translates different data representations from the
Application layer into uniform standard format
• Providing services for secure efficient data
transmission
 e.g. data encryption, and data compression.
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Layer 5: Session Layer
• Allows two applications on different computers to
establish, use, and end a session.
 e.g. file transfer, remote login
• Establishes dialog control
 Regulates which side transmits, plus when and how
long it transmits.
• Performs token management and
synchronization.
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Layer 4: Transport Layer
• Manages transmission packets
 Repackages long messages when necessary into
small packets for transmission
 Reassembles packets in correct order to get the
original message.
• Handles error recognition and recovery.
 Transport layer at receiving acknowledges packet
delivery.
 Resends missing packets
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Layer 3: Network Layer
• Manages addressing/routing of data within the
subnet
 Addresses messages and translates logical addresses and
names into physical addresses.
 Determines the route from the source to the destination
computer
 Manages traffic problems, such as switching, routing, and
controlling the congestion of data packets.
• Routing can be:
 Based on static tables
 determined at start of each session
 Individually determined for each packet, reflecting the
current network load.
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Layer 2: Physical Layer
 Packages raw bits from the Physical layer into frames (logical,
structured packets for data).
 Provides reliable transmission of frames
 It waits for an acknowledgment from the receiving computer.
 Retransmits frames for which acknowledgement not received
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Layer 1: Physical Layer
• Transmits bits from one computer to another
• Regulates the transmission of a stream of bits over a
physical medium.
• Defines how the cable is attached to the network
adapter and what transmission technique is used to
send data over the cable. Deals with issues like
 The definition of 0 and 1, e.g. how many volts represents
a 1, and how long a bit lasts?
 Whether the channel is simplex or duplex?
 How many pins a connector has, and what the function
of each pin is?
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Internet Protocols vs OSI
• Explicit
Presentation and
session layers
missing in Internet
Protocols
• Data Link and
Network Layers
redesigned
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
TCP
IP
Network Interface
Hardware
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Services in the OSI Model
• In OSI model, each layer provide services to layer
above, and ‘consumes’ services provided by layer
below.
• Active elements in a layer called entities.
• Entities in same layer in different machines called
peer entities.
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IPSEC
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Secure Socket Layer (SSL):
• SSL is an Internet protocol used for secure exchange of
Information between a web browser and web server
Provides two basic services
 Authentication
 Confidentiality
• Logically it provides secure pipe between the web browser and
web server
• SSL is developed by Netscape corporation in 1994 since then SSL
becomes the world most popular web security mechanism
• SSL is supported by all web browsers available in the market
• SSL comes in three version 2 , 3 and 3.1
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Conceptual Positioning of SSL
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Working of SSL
SSL has three sub protocols namely
1. Handshake protocol
2. Record protocol
3. Alert protocol
Above three sub protocols constitute the overall working of SSL
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Record Protocol
• Record protocol in SSL comes into picture after completion of
successful handshake between client and server
• This protocol provides two services to an SSL connection as follows
• Confidentiality: Achieved by using the secret key that is defined by
handshake protocol
• Integrity: Handshake protocol also defines a shared secret key
(MAC) that is used for assuring the message integrity
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Alert Protocol
 When either client or server detects an error the
detecting party sends an alert message to the other part
 If error is fatal both parties immediately close
connection and destroy session identifier and secret key
associated with this connection
 Non secure errors do not result in the termination of
connection , instead the parties handle the error and
continue session
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Transport layer security (TLS)
• SSL is also called as TLS after version 3.0
• Transport layer security service
• Originally developed by Netscape
• Version-3 developed with public I/P
• Subsequently become Internet standard known as TLS (Transport
layer security)
• Uses TCP to provide a reliable end – to – end service
• SSL has two layers of protocol
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SSL/TLS Architecture
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TLS (Transport Layer Security)
• IETF Standard RFC-2246 similar to SSL Version 3 with following
minor differences
• Record format version no
• HMAC and MAC
• Pseudo random function to expand the secrets
• Additional alert codes
• Change in supported ciphers
• Change in certificate negotiation
• Change in use of padding
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Web Development
Strategies
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Web Development Strategy
• Phases of web publishing
• Planning: Setting goals specifying contents, organizing content and setting user
interface to navigate content
• Implementation: Creating content, implementing navigation, user interface
and coding site which may include HTML, scripts, programs and database
developments
• Testing: User browser and system testing (ie same page may appear differently
on different browsers so check it on all the available browsers in market)
• Domain Registration & Hosting: Based on the importance of site register for
unique or sub domain and host it on respective domain by performing ftp
• Website Promotion: Promote your site by registering it on search engines and
indexes to increase the hit rate
• Maintenance: Maintaining and updating the site, questioning the old goals and
returning to planning phase
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Planning Phase
• Identify your target audience
• Materialize the concept and ideas
• Selection of Web page lay outing schemes
• Finalizing directory structure
• Developing look and feel related with representation of color,
graphics etc
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Identifying Target Audience
• Audiences background and their previous experiences
• Their interest’s and their tastes
• The reason why they are visiting your site
• What their age is?
• What they are expecting from your website
• Age of the audience
• Gender
• Financial status
• Educational background
• Geographical Location
• Material status
• Any other relevant point
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Materialize your Concept and Ideas
• To inform
• To promote a product
• To educate the audiences
• To do research and report
• To entertain the audience
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WebPage Lay outing - Tree
Structure
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U-2
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Depth Vs Breadth

Pure Linear
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Linear With Alternate
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Linear with Option
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Linear with side tour
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Mixed Hierarchy
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Pure Web
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Grid Layout
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Linear
Hierarchy
Pure Web
Grid
Possibility of confusion
Expressiveness
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Transmission Media
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Transmission Media
• Twisted-Pair Cable
• Coaxial Cable
• Fiber-Optic Cable
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Twisted Pair Cable
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Twisted Pair
• Twisted-pair is a type of cabling that is used for
telephone communications and most modern
Ethernet networks.
• A pair of wires forms a circuit that can transmit
data.
• The pairs are twisted to provide protection
against crosstalk, the noise generated by
adjacent pairs.
• There are two basic types, shielded twisted-pair
(STP) and unshielded twisted-pair (UTP).
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Twisted Pair
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Effect of noise on parallel lines
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Effect of noise on twisted pair
lines
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Unshielded Twisted Pair
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Unshielded Twisted Pair
• Consists of 4 pairs (8 wires) of
insulated copper wires typically about
1 mm thick.
• The wires are twisted together in a
helical form.
• Twisting reduces the interference
between pairs of wires.
• High bandwidth and High attenuation
channel.
• Flexible and cheap cable.
• Category rating based on number of
twists per inch and the material used
• CAT 3, CAT 4, CAT 5, Enhanced CAT 5
and now CAT 6.
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UTP Categories
• UTP comes in several categories that are based on the
number of twists in the wires, the diameter of the wires
and the material used in the wires.
• Category 3 is the wiring used primarily for telephone
connections.
• Category 5e and Category 6 are currently the most common
Ethernet cables used.
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Categories of UTP : CAT3
• Bandwidth 16 Mhz
• 11.5 dB Attenuation
• 100 ohms Impedance
• Used in voice applications and 10baseT (10Mbps)
Ethernet
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Categories of UTP: CAT 4
• 20 MHz Bandwidth
• Used in 10baseT (10Mbps) Ethernet
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• Used for high-speed data transmission
• Used in 10BaseT (10 Mbps) Ethernet & Fast Ethernet (100
Mbps)
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Categories of UTP: CAT 5e
• Transmits high-speed data
• Used in Fast Ethernet (100 Mbps), Gigabit Ethernet (1000
Mbps) & 155 Mbps ATM
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• Transmits high-speed data
• Used in Gigabit Ethernet (1000 Mbps) & 10 Gig Ethernet
(10000 Mbps)
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Shielded Twisted Pair (STP)
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Shielded Twisted Pair
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Coaxial Cable

Coaxial Cable
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Categories of Coaxial Cable
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Category Impedance Use
RG-59 75 W Cable TV
RG-58 50 W Thin Ethernet
RG-11 50 W Thick Ethernet
Radio Government (RG) rating

BNC Connectors
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Fiber Optic Cable
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Fiber Optics
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Glass or Plastic
125 um

Fiber Optics
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Propagation Modes
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Modes
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Fiber Types
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Type Core Cladding Mode
50/125 50 125 Multimode, graded-index
62.5/125 62.5 125 Multimode, graded-index
100/125 100 125 Multimode, graded-index
7/125 7 125 Single-mode

Fiber Construction
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Fiber-optic Connectors
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Fiber Optic Connectors
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FC connector
SC connector
ST connector

Web Application Architecture:
multi-tier (2-tier, 3-tier) & mvc
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Significance of Tiers
• N-tier architectures have the same
components
o Presentation
o Business/Logic
o Data
• N-tier architectures try to separate the
components into different tiers/layers
o Tier: physical separation
o Layer: logical separation
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Significance of “Tiers”
Database runs on Server
o Separated from client
o Easy to switch to a different database
Presentation and logic layers still tightly
connected
o Heavy load on server
o Potential congestion on network
o Presentation still tied to business logic
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1-Tier Architecture
All 3 layers are on the same machine
o All code and processing kept on a single machine
Presentation, Logic, Data layers are tightly connected
o Scalability: Single processor means hard to increase volume of
processing
o Portability: Moving to a new machine may mean rewriting
everything
o Maintenance: Changing one layer requires changing other
layers
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2-Tier Architecture
Database runs on Server
o Separated from client
o Easy to switch to a different database
Presentation and logic layers still tightly
connected (coupled)
o Heavy load on server
o Potential congestion on network
o Presentation still tied to business logic
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3-Tier Architecture
o Each layer can potentially run on a different
machine
o Presentation, logic, data layers disconnected
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Browser
client Browser sends
URL to web server,
requesting a file or
program
Web
server
Fetches file or runs
server side (php) script
Server returns results
file and/or program outputs
Browser displays
("renders") resulting page
3-Tier Architecture
MySQL
Database
SQL commands sent
- results returned
HTML5
PHP
SQL
MySQL
Javascript - runs inside browser
jQuery AJAX - allows server connection
Javascript
HTTP (developer tools)
Apache
web
server
PHP
script
AJAX, jQuery notation
JSON, web services
CSS
phpMyAdmin
provides separate
browser-based
interface
Full stack development
Integrated development
Command Line Interfaces
(MobaXterm) provides
another DB interface
mysql commands -- performance
php CLI -- error reporting
also online meandeviation.com syntax tool
CLI for PHP
and mysql
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The 3-Tier Architecture for Web
Apps
Presentation Layer
 Static or dynamically generated content rendered by the
 browser (front-end)
Logic Layer
 A dynamic content processing and generation level
 application server, e.g., Java EE, ASP.NET, PHP, ColdFusion
 platform (middleware)
Data Layer
 A database, comprising both data sets and the database
 management system or RDBMS software that manages and provides access to
the data (back-end)
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3-Tier Architecture - Advantages
• Independence of Layers
• Easier to maintain
• Components are reusable
• Faster development (division of work)
 Web designer does presentation
 Software engineer does logic
 DB admin does data model
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Questions Appeared in Previous year University Examination:
Nov – Dec 2013
a) Differentiate between Internet and Intranet? – 2m
b) Describe Asynchronous, Synchronous and isosynchronous mode of Transmission? - 7M
c) What are the various ways to connect to Internet? – 7M
d) What is videoconferencing? Also explain the concept of e-mail Sending and Receiving - 7M
Nov – Dec 2014
a) Explain the significance of logical address – 2m
b) Describe Asynchronous, Synchronous and isosynchronous mode of Transmission? - 7M
c) Draw and explain twisted pair and coaxial cable. – 7M
d) What is WAN explain different types of Internet Services. - 7M
April - May 2014
a) What is transmission mode? – 2m
b) Explain Two tier and three tier architecture of web application with neat sketch - 7M
c) Describe the types of computer network with block diagram - 7M
d) Write short note on (i) e-mail and (ii) Videoconferencing - 7M

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Questions Appeared in Previous year University Examination …
Nov – Dec 2015
a) What is intranet and Internet – 2m
b) Draw a block diagram showing how end users are sending and receiving data packets by specifying the
protocols and interfacing components in use? - 7M
c) How information does is passing from one OSI Layer to another OSI Layer. – 7M
d) Define LAN , MAN and WAN , Write down pros and cons of having a computer in educational Institution and
also suggest to overcome the laws from network - 7M
Nov – Dec 2016
a) What is protocol? – 2m
b) Write a short note on (i) Choosing an ISP and (ii) Protocol Governing the Web - 7M
c) Explain in brief about e-mail concept and sending and receiving secure e-mail. – 7M
d) Discuss the various type of transmission modes - 7M

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Questions Appeared in Previous year University Examination …
April – May 2017
a) What is LAN ? – 2m
b) Why are layered structures used in computer networks ? What are the protocols governing the web - 7M
c) How will you explain transmission mode ? What are the classifications of transmission mode?. – 7M
d) Explain the concept of sending and receiving secure e-mail- 7M
Nov – Dec 2018
a) What is protocol ? – 2m
b) What is LAN, MAN and WAN - 7M
c) What is ISP? Describe Internet Services . – 7M
d) Write short note on e-mail- 7M

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