E Commerce

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Department of Commerce & Finance
GC UNIVERSITY LAHORE
Major:
B.COM (HONS)
Submitted By:
IHTISHAM AHMAD
Roll No:
2355R-B.com-18
Submitted To:
SIR ASIF SARWAR
Course Title:
E-COMMERCE
Semester:
SUMMER SEMESTER
SECTION:
A
Assignment Title:
NETWORK TYPES AND TOPOLOGY

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What are Networks and Types?
A network consists of two or more computers that are linked to share resources (such as printers
and CDs), exchange files, or allow electronic communications. The computers on a network
may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.
1. Personal Area Network (PAN)
The smallest and most basic type of network, a PAN is made up of a wireless modem, a
computer or two, phones, printers, tablets, etc., and revolves around one person in one building.
These types of networks are typically found in small offices or residences and are managed by
one person or organization from a single device.
2. Local Area Network (LAN)
We’re confident that you’ve heard of these types of networks before – LANs are the most
frequently discussed networks, one of the most common, one of the most original, and one of
the simplest types of networks. LANs connect groups of computers and low-voltage devices
across short distances (within a building or between a group of two or three buildings close
nearer) to share information and resources. Enterprises typically manage and maintain LANs.
Using routers, LANs can connect to wide area networks (WANs, explained below) to rapidly
and safely transfer data.
3. Wireless Local Area Network (WLAN)
Functioning like a LAN, WLANs make use of wireless network technology, such as Wi-Fi.
Typically seen in the same types of applications as LANs, these types of networks don’t require
that devices rely on physical cables to connect to the network.
4. Campus Area Network (CAN)
Larger than LANs, but smaller than metropolitan area networks (MANs, explained below),
these types of networks are typically seen in universities, large K-12 school districts, or small
businesses. They can be spread across several buildings that are fairly close to each other so
users can share resources.
5. Metropolitan Area Network (MAN)
These types of networks are larger than LANs but smaller than WANs – and incorporate
elements from both types of networks. MAN spans an entire geographic area (typically a town
or city, but sometimes a campus). Ownership and maintenance areas are handled by either a
single person or a company (a local council, a large company, etc.).
6. Wide Area Network (WAN)
Slightly more complex than a LAN, a WAN connects computers across longer physical
distances. This allows computers and low-voltage devices to be remotely connected to each o
large network to communicate even when they’re miles apart.
The Internet is the most basic example of a WAN, connecting all computers around the world.
Because of a WAN’s vast reach, it is typically owned and maintained by multip le
administrators or the public.
7. Storage-Area Network (SAN)
As a dedicated high-speed network that connects shared pools of storage devices to several
servers, these types of networks don’t rely on a LAN or WAN. Instead, they move storage

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resources away from the network and place them into their high-performance network. SANs
can be accessed in the same fashion as a drive attached to a server. Types of storage-area
networks include converged, virtual, and, unified SANs.
8. System-Area Network (also known as SAN)
This term is fairly new within the past two decades. It is used to explain a relatively local
network that is designed to provide high-speed connection in server-to-server applications
(cluster environments), storage area networks (called “SANs” as well), and processor-to-
processor applications. The computers connected on a SAN operate as a single system at very
high speeds.
9. Passive Optical Local Area Network (POLAN)
As an alternative to traditional switch-based Ethernet LANs, POLAN technology can be
integrated into structured cabling to overcome concerns about supporting traditional Ethernet
protocols and network applications such as PoE (Power over Ethernet). A point-to-multipoint
LAN architecture, POLAN uses optical splitters to split an optical signal from one strand of
single-mode optical fiber into multiple signals to serve users and devices.
10. Enterprise Private Network (EPN)
These types of networks are built and owned by businesses that want to securely connect their
various locations to share computer resources.
11. Virtual Private Network (VPN)
By extending a private network across the Internet, a VPN lets its users send and receive data
as if their devices were connected to the private network – even if they’re not. Through a virtual
point-to-point connection, users can access a private network remotely.

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What are network topology and types?
Topology defines the structure of the network of how all the components are interconnected to
each other. There are two types of topology: physical and logical topology.
Physical topology is the geometric representation of all the nodes in a network.
Topology is derived from two Greek words topo and logy, where topo means 'place' and
logy means 'study'. In computer networks, a topology is used to explain how a network
is physically connected and the logical flow of information in the network. A topology
mainly describes how devices are connected and interact with each other using
communication links.
In computer networks, there are mainly two types of topologies, they are:
1. Physical Topology: A physical topology describes how the computers or nodes are
connected in a computer network. It is the arrangement of various elements(link,
nodes, etc.), including the device location and code installation of a computer
network. In other words, we can say that it is the physical layout of nodes,
workstations, and cables in the network.
2. Logical Topology: A logical topology describes the way, data flow from one
computer to another. It is bound to a network protocol and defines how data is moved
throughout the network and which path it takes. In other words, it is how the devices
communicate internally.
Network topology defines the layout, virtual shape, or structure of the network, not only
physically but also logically. A network can have one physical topology and multiple
logical topologies at the same time.

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In this blog, we will mainly concentrate on physical topologies. We'll learn about different
types of physical topologies, their advantages, and their disadvantages.
In a computer network, there are mainly six types of physical topology, they are:
1. Bus Topology
2. Ring Topology
3. Star Topology
4. Mesh Topology
5. Tree Topology
6. Hybrid Topology
Now let us learn these topologies one by one:
Bus Topology
Bus topology is the simplest kind of topology in which a common bus or channel is used
for communication in the network. The bus is connected to various taps and
droplines. Taps are the connectors, while droplines are the cables connecting the bus with
the computer. In other words, there is only a single transmission line for all nodes.

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When a sender sends a message, all other computers can hear it, but only the receiver accepts
it(verifying the mac address attached with the data frame) and others reject it. Bus technology
is mainly suited for small networks like LAN, etc.
In this topology, the bus acts as the backbone of the network, which joins every computer
and peripherals in the network. Both ends of the shared channel have line terminators. The
data is sent only in one direction and as soon as it reaches the end, the terminator removes
the data from the communication line(to prevent signal bounce and data flow disruption).
In a bus topology, each computer communicates to another computer on the network
independently. Every computer can share the network's total bus capabilities. The devices
share the responsibility for the flow of data from one point to the other in the network.
For Example Ethernet cable, etc.
Following are the advantages of Bus topology:
1. Simple to use and install.
2. If a node fails, it will not affect other nodes.
3. Less cabling is required.
4. Cost-efficient to implement.

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Following are the disadvantages of Bus topology:
1. Efficiency is less when nodes are more(strength of signal decreases).
2. If the bus fails, the network will fail.
3. A limited number of nodes can connect to the bus due to limited bus length.
4. Security issues and risks are more as messages are broadcasted to all nodes.
5. Congestion and traffic on the bus as it is the only source of communication.
Ring Topology
Ring topology is a topology in which each computer is connected to exactly two other
computers to form the ring. The message passing is unidirectional and circular.
This network topology is deterministic, i.e., each computer is given access for transmission
at a fixed time interval. All the nodes are connected in a closed loop. This topology mainly
works on a token-based system and the token travels in a loop in one specific direction.
In a ring topology, if a token is free then the node can capture the token and attach the data
and destination address to the token, and then leaves the token for communication. When this
token reaches the destination node, the data is removed by the receiver, and the token is made
free to carry the next data. For Example, Token Ring, etc.

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Following are the advantages of Ring topology:
1. Easy Installation.
2. Less Cabling Required.
3. Reduces chances of data collision(unidirectional).
4. Easy to troubleshoot(the faulty node does not pass the token).
5. Each node gets the same access time.
Following are the disadvantages of Ring topology:
1. If a node fails, the whole network will fail.
2. Slow data transmission speed(each message has to go through the ring path).
3. Difficult to reconfigure(we have to break the ring).
Star Topology
Star topology is a computer network topology in which all the nodes are connected to a
centralized hub. The hub or switch acts as a middleware between the nodes. Any node
requesting for service or providing service, first contact the hub for communication.

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The central device(hub or switch) has point to point communication link(the dedicated link
between the devices which can not be accessed by some other computer) with the devices.
The central device then broadcasts or unicasts the message based on the central device used.
The hub broadcasts the message, while the switch unicasts the messages by maintaining a
switch table. Broadcasting increases unnecessary data traffic in the network.
In a star topology, the hub and switch act as a server, and the other connected devices act as
clients. Only one input-output port and one cable are required to connect a node to the central
device. This topology is better in terms of security because the data does not pass through
every node. For Example High-Speed LAN, etc.
Following are the advantages of Star topology:
1. Centralized control.
2. Less Expensive.
3. Easy to troubleshoot(the faulty node does not give a response).
4. Good fault tolerance due to centralized control on nodes.
5. Easy to scale(nodes can be added or removed from the network easily).
6. If a node fails, it will not affect other nodes.
7. Easy to reconfigure and upgrade(configured using a central device).
Following are the disadvantages of Star topology:
1. If the central device fails, the network will fail.
2. The number of devices in the network is limited(due to the limited input-output port
in a central device).
Mesh Topology
Meshtopology is a computer network topology in which nodes are interconnected with
each other. In other words, direct communication takes place between the nodes in the
network.

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There are mainly two types of Mesh:
1. Full Mesh: In which each node is connected to every other node in the network.
2. Partial Mesh: In which, some nodes are not connected to every node in the network.
In a fully connected mesh topology, each device has a point-to-point link with every other
device in the network. If there are 'n' devices in the network, then each device has
exactly '(n-1)' input-output ports and communication links. These links are simplex, i.e., the
data moves only in one direction. A duplex link(in which data can travel in both directions
simultaneously) can replace two simplex links.
If we are using simplex links, then the number of communication links will be 'n(n-
1)' for 'n' devices, while it is 'n(n-1)/2' if we are using duplex links in the mesh topology.
For Example, the Internet(WAN), etc.
Following are the advantages of Mesh topology:
1. Dedicated links facilitate direct communication.
2. No congestion or traffic problems on the channels.
3. Good Fault tolerance due to the dedicated path for each node.

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4. Very fast communication.
5. Maintains privacy and security due to a separate channel for communication.
6. If a node fails, other alternatives are present in the network.
Following are the disadvantages of Mesh topology:
1. Very high cabling is required.
2. Cost inefficient to implement.
3. Complex to implement and takes large space to install the network.
4. Installation and maintenance are very difficult.
5. Tree Topology:
Tree topology is a computer network topology in which all the nodes are directly or
indirectly connected to the main bus cable. Tree topology is a combination of Bus and Star
topology.
In a tree topology, the whole network is divided into segments, which can be easily managed
and maintained. There is a main hub and all the other sub-hubs are connected in this topology.
Following are the advantages of Tree topology:

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1. Large distance network coverage.
2. Fault finding is easy by checking each hierarchy.
3. Least or no data loss.
4. A Large number of nodes can be connected directly or indirectly.
5. Other hierarchical networks are not affected if one of them fails.
Following are the disadvantages of Tree topology:
1. Cabling and hardware cost is high.
2. Complex to implement.
3. Hub cabling is also required.
4. A large network using tree topology is hard to manage.
5. It requires very high maintenance.
6. If the main bus fails, the network will fail.
Hybrid Topology:
A hybrid topology is a computing topology that is a combination of two or more
topologies. In practical use, they are the most widely used.

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In this topology, all topologies are interconnected according to the need to form a hybrid. All
the good features of each topology can be used to make an efficient hybrid topology.
Following are the advantages of Hybrid topology:
1. It can handle a large volume of nodes.
2. It provides flexibility to modify the network according to our needs.
3. Very Reliable(if one node fails it will not affect the whole network).
Following are the disadvantages of Hybrid topology:
1. Complex design.
2. Expensive to implement.
3. Multi-Station Access Unit(MSAL) required.
Hence, after learning the various computer network topologies, we can conclude that some
points need to be considered when selecting a physical topology:
 Ease of Installation.
 Fault Tolerance.
 Implementation Cost.
 Cabling Required.
 Maintenance Required.
 Reliable Nature.
 Ease of Reconfiguration and upgradation.

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Data Communication and its Elements
Data Communication is defined as the exchange of data between two devices via some
form of transmission media such as a cable, wire or it can be air or vacuum also. For
the occurrence of data communication, communicating devices must be a part of a
communication system made up of a combination of hardware or software devices
and programs.
There are mainly five Elements of a data communication system:
1. Message
2. Sender
3. Receiver
4. Transmission Medium
5. Set of rules (Protocol)
All above-mentioned elements are described below:
Figure – Components of Data Communication System
1. Message :
This is a most useful asset of a data communication system. The message
simply refers to data or a piece of information that is to be
communicated. A message could be in any form, it may be in form of a
text file, an audio file, a video file, etc.

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2. Sender
To transfer a message from source to destination, someone must be there
who will play the role of a source. The sender plays the part of a source
in a data communication system. It is simply a device that sends data
messages. The device could be in form of a computer, mobile, telephone,
laptop, video camera, workstation, etc.
3. Receiver
It is a destination where finally the message sent to the source has
arrived. It is a device that receives messages safely. Same as the sender,
the receiver can also be in form of a computer, telephone mobile,
workstation, etc.
4. Transmission
In the entire process of data communication, there must be something
that could act as a bridge between sender and receiver, Transmission
medium plays that part. It is the physical path by which data or message
travels from sender to receiver. Transmission medium could be guided
(with wires) or unguided (without wires), for example, twisted pair
cable, fiber optic cable, radio waves, microwaves, etc.
5. Protocol
To govern data communications, various sets of rules had been already
designed by the designers of the communication systems, which
represent a kind of agreement between communicating devices. These
are defined as protocol. In simple terms, the protocol is a set of rules that
govern data communication. If two different devices are connected but
there is no protocol among them, there would not be any kind of
communication between those two devices. Thus the protocol is
necessary for data communication to take place.
A typical example of a data communication system is sending an e-mail. The user
which sends email act as a sender, the message is data that which user wants to send,
and the receiver is the one to whom the user wants to send a message, there are many
protocols involved in this entire process, and one of them is Simple Mail Transfer
Protocol (SMTP), both sender and receiver must have an internet connection which
uses a wireless medium to send and receive email.