Assignment 1

Computer Networks
ASSIGMENT-1
SUBMITTED TO
Pranab Bandhu Nath
Senior Lecturer
CSE Department
City University, Dhaka
SUBMITTED BY
NAME :MD HASNAIN
ID :1834902583
Department of CSE City University, Dhaka.

Basic concept of Computer networks
and
distributed systems
Computer networks:
Today computer networks are everywhere.
You will find them in homes, offices, factories, hospitals leisure centres
etc.
But how are they created? What technologies do they use?
In this tutorial you will learn the basic networking technologies, terms
and concepts used in all types of networks both wired and wireless,
home and office.
Home and Office Networks
The network you have at home uses the same networking technologies,
protocols and services that are used in large corporate networks and on
the Internet.
The only real difference between an home network and a large
corporate network is the size.
A home network will have between 1 and 20 devices and a corporate
network will have many thousands.

If you are completely new to networking then the basic course will
introduce you to the basic networking protocols used in small
home/office networks and on the Internet.
Setting Up and building a Home Network will introduce some basic
networking component and show you how to build a home network
and connect it to the Internet.
Networking Types and Structures
Networks can be wired or wireless with most networks being a mixture
of both.
Wired Networks- Advantages and Disadvantages
Advantages:
 Ethernet ports are found on almost all laptops/PCs and netbooks
even on those 8 years old.
 Wired networks are faster than Wireless. Data rates were
periodically increased from the original 10 megabits per second,
to 1gigabits per second. Most home networks use 10-100Mbps.
 More secure than Wireless
Disadvantages:
 Need to Use cable which can be unsightly, difficult to run and
expensive.
 Can’t be used easily between buildings (planning etc).
 Note a new technology that uses mains cable overcomes many of
these disadvantages. Powerline networking is common on
home/small office networks
 Not supported on Mobile phones and tablets.

Wireless Networks – Advantages and Disadvantages
Advantages:
 Generally easier to set up.
 Can be used both on home and public networks
 No cables required.
 Can be used with mobile phones and tablets.
Disadvantages:
 Generally Slower than wired networks.
 Limited by range.
 Open to eavesdropping.
 Not as secure depending on set up.
Networking Topologies and Layout
There are many different ways network nodes can be connected
together. This isn’t normally a consideration in small networks but has
networks get larger it becomes more important.
star-topology There are many different ways network nodes can be
connected together.
Common connection technologies like Wi-Fi, Bluetooth etc are
designed to work using a particular network topology.

When designing networks and choosing connection protocols having an
understanding of these topologies is important.
Common are:
 Bus
 Ring
 Mesh
 Star
 Hybrid
Each of these topologies has advantages and disadvantages this
Network topologies article has a really good overview of each topology
along with advantages and disadvantages.
Early Ethernet networks used a bus structure, modern Ethernet
networks and Wi-Fi Networks. use a star bus (hybrid) structure.
Networking Topology- Physical vs Logical
How the nodes on a network communicate with each other can be very
different to how they are physically interconnected.
Most Home and small office networks use a physical bus topology.
Common logical typologies are Peer to Peer and Client Server.
The web (WWW) is a client server network at the logical level.
Peer to Peer and Client Server Networking

Peer to Peer:
In a peer to peer network all nodes are equal and any node can talk to
any other node.
No node has any special role. This was the original networking model of
windows networking. (Windows for Workgroups)- Diagram below:
Advantages and Disadvantages
Advantages:
 Easier to setup
 Not dependent on a single node
 More resilient
 Better distribution of network traffic
 No central administrator required

 Less expensive hardware required
Disadvantages:
 Less secure and more difficult to secure
 More difficult to administer
 More difficult to backup
 More difficult to locate information.
Client Server:
In a Client Server network a server has a special role e.g file server,
domain controller, web server etc.
A client connects to a server to use the appropriate services.
This is the networking model used on the web and the Internet and on
modern large Windows networks.-Diagram below:

Advantages and Disadvantages
Advantages:
 Easy to find resources as they are on a dedicated node i.e. A
server
 Easy to secure
 Easy to administer
 Easy to backup
Disadvantages:
 Servers are a single point of failure
 Expensive hardware required
 Network traffic get concentrated

Network Size
A protocol defines a set of rules that govern how computers talk to
each other.
PAN -Personal Area Network – Linking local devices e,g, PC to
printer
LAN – Local Area network- links devices in an office or offices
MAN – Metropolitan Area network – links devices across multiple
buildings like a campus
WAN – Wide area network – links devices across a
country/countries.
Networking Levels and Layers and Protocols
A protocol defines a set of rules that govern how computers talk to
each other.
Ethernet and Wi-Fi are Data link protocols that are responsible for
framing data on the media (cable or wireless).
They can be used for carrying higher level protocols (IP etc)..
Ethernet and Wi-Fi use a physical level address know as the MAC
address which is 48 bits.
EUI 64 addresses are MAC addresses with 64 bits will replace MAC
addresses on IPV6, 6LoWPAN, ZigBee and other new network
protocols. See this Wiki for details.

You can divide networking into distinct levels or layers.
Each level or layer is responsible for a particular function.
The OSI uses a 7 layer model and TCP/IP networks use a 4 layer model.
Because TCP/IP networks are the most common the TCP/IP model is
the most important one to understand. The levels are:
 Data link level – e.g. Ethernet, Wi-Fi
 Networking e.g. IP, – IPv4 Address classes and subnetting and IPv6
Explained for Beginners.
 Transport level e.g.TCP, UDP – See TCP vs UDP
 Application level – e.g. HTTP -See HTTP for beginners
Network Addressing
IP Address:
An IP address is a unique address that identifies a device on the
internet or a local network. IP stands for "Internet Protocol," which is
the set of rules governing the format of data sent via the internet or
local network.
An IP address is a string of numbers separated by periods. IP addresses
are expressed as a set of four numbers — an example address might be
192.158.1.38. Each number in the set can range from 0 to 255. So, the
full IP addressing range goes from 0.0.0.0 to 255.255.255.255.

IP addresses are not random. They are mathematically produced and
allocated by the Internet Assigned Numbers Authority (IANA), a division
of the Internet Corporation for Assigned Names and Numbers (ICANN).
ICANN is a non-profit organization that was established in the United
States in 1998 to help maintain the security of the internet and allow it
to be usable by all. Each time anyone registers a domain on the
internet, they go through a domain name registrar, who pays a small
fee to ICANN to register the domain.
How do IP addresses work :
If you want to understand why a particular device is not connecting in
the way you would expect or you want to troubleshoot why your
network may not be working, it helps understand how IP addresses
work.
Internet Protocol works the same way as any other language, by
communicating using set guidelines to pass information. All devices
find, send, and exchange information with other connected devices
using this protocol. By speaking the same language, any computer in
any location can talk to one another.
The use of IP addresses typically happens behind the scenes. The
process works like this:
I. Your device indirectly connects to the internet by connecting at
first to a network connected to the internet, which then grants
your device access to the internet.

II. When you are at home, that network will probably be your
Internet Service Provider (ISP). At work, it will be your company
network.
III. Your IP address is assigned to your device by your ISP.
IV. Your internet activity goes through the ISP, and they route it back
to you, using your IP address. Since they are giving you access to
the internet, it is their role to assign an IP address to your device.
V. However, your IP address can change. For example, turning your
modem or router on or off can change it. Or you can contact your
ISP, and they can change it for you.
VI. When you are out and about – for example, traveling – and you
take your device with you, your home IP address does not come
with you. This is because you will be using another network (Wi-Fi
at a hotel, airport, or coffee shop, etc.) to access the internet and
will be using a different (and temporary) IP address, assigned to
you by the ISP of the hotel, airport or coffee shop.
Types of IP addresses
There are different categories of IP addresses, and within
each category, different types.
Consumer IP addresses:
Every individual or business with an internet service plan will have two
types of IP addresses: their private IP addresses and their public IP
address. The terms public and private relate to the network location —

that is, a private IP address is used inside a network, while a public one
is used outside a network.
Private IP addresses:
Every device that connects to your internet network has a private IP
address. This includes computers, smartphones, and tablets but also
any Bluetooth-enabled devices like speakers, printers, or smart TVs.
With the growing internet of things, the number of private IP addresses
you have at home is probably growing. Your router needs a way to
identify these items separately, and many items need a way to
recognize each other. Therefore, your router generates private IP
addresses that are unique identifiers for each device that differentiate
them on the network.
Public IP addresses:
A public IP address is the primary address associated with your whole
network. While each connected device has its own IP address, they are
also included within the main IP address for your network. As described
above, your public IP address is provided to your router by your ISP.
Typically, ISPs have a large pool of IP addresses that they distribute to
their customers. Your public IP address is the address that all the
devices outside your internet network will use to recognize your
network.
Dynamic IP addresses:
Dynamic IP addresses change automatically and regularly. ISPs buy a
large pool of IP addresses and assign them automatically to their
customers. Periodically, they re-assign them and put the older IP
addresses back into the pool to be used for other customers. The

rationale for this approach is to generate cost savings for the ISP.
Automating the regular movement of IP addresses means they don’t
have to carry out specific actions to re-establish a customer's IP address
if they move home, for example. There are security benefits, too,
because a changing IP address makes it harder for criminals to hack into
your network interface.
Static IP addresses:
In contrast to dynamic IP addresses, static addresses remain consistent.
Once the network assigns an IP address, it remains the same. Most
individuals and businesses do not need a static IP address, but for
businesses that plan to host their own server, it is crucial to have one.
This is because a static IP address ensures that websites and email
addresses tied to it will have a consistent IP address — vital if you want
other devices to be able to find them consistently on the web.
There are two types of website IP addresses:
For website owners who don’t host their own server, and instead rely
on a web hosting package – which is the case for most websites – there
are two types of website IP addresses. These are shared and dedicated.
Shared IP addresses:
Websites that rely on shared hosting plans from web hosting providers
will typically be one of many websites hosted on the same server. This
tends to be the case for individual websites or SME websites, where
traffic volumes are manageable, and the sites themselves are limited in
terms of the number of pages, etc. Websites hosted in this way will
have shared IP addresses.

Dedicated IP addresses:
Some web hosting plans have the option to purchase a dedicated IP
address (or addresses). This can make obtaining an SSL certificate easier
and allows you to run your own File Transfer Protocol (FTP) server. This
makes it easier to share and transfer files with multiple people within
an organization and allow anonymous FTP sharing options. A dedicated
IP address also allows you to access your website using the IP address
alone rather than the domain name — useful if you want to build and
test it before registering your domain.
Distributed systems:
A distributed system, also known as distributed computing, is a system
with multiple components located on different machines that
communicate and coordinate actions in order to appear as a single
coherent system to the end-user.
Overview
The machines that are a part of a distributed system may be
computers, physical servers, virtual machines, containers, or any other
node that can connect to the network, have local memory, and
communicate by passing messages.
There are two general ways that distributed systems function:
1. Each machine works toward a common goal and the end-user
views results as one cohesive unit.
2. Each machine has its own end-user and the distributed system
facilitates sharing resources or communication services.

Although distributed systems can sometimes be obscure, they usually
have three primary characteristics: all components run concurrently,
there is no global clock, and all components fail independently of each
other.
Benefits and challenges of distributed systems
There are three reasons that teams generally decide to implement
distributed systems:
 Horizontal Scalability—Since computing happens independently
on each node, it is easy and generally inexpensive to add
additional nodes and functionality as necessary.
 Reliability—Most distributed systems are fault-tolerant as they
can be made up of hundreds of nodes that work together. The
system generally doesn’t experience any disruptions if a single
machine fails.
 Performance—Distributed systems are extremely efficient
because work loads can be broken up and sent to multiple
machines.
However, distributed systems are not without challenges. Complex
architectural design, construction, and debugging processes that are
required to create an effective distributed system can be
overwhelming.
Three more challenges you may encounter include:

 Scheduling—A distributed system has to decide which jobs need
to run, when they should run, and where they should run.
Schedulers ultimately have limitations, leading to underutilized
hardware and unpredictable runtimes.
 Latency—The more widely your system is distributed, the more
latency you can experience with communications. This often leads
to teams making tradeoffs between availability, consistency, and
latency.
 Observability—Gathering, processing, presenting, and monitoring
hardware usage metrics for large clusters is a significant
challenge.
How a Distributed System Works
Hardware and software architectures are used to maintain a distributed
system. Everything must be interconnected—CPUs via the network and
processes via the communication system.
Types of distributed systems
Distributed systems generally fall into one of four different basic
architecture models:
I. Client-server—Clients contact the server for data, then format it
and display it to the end-user. The end-user can also make a
change from the client-side and commit it back to the server to
make it permanent.
II. Three-tier—Information about the client is stored in a middle tier
rather than on the client to simplify application deployment. This
architecture model is most common for web applications.

III. n-tier—Generally used when an application or server needs to
forward requests to additional enterprise services on the
network.
IV. Peer-to-peer—There are no additional machines used to provide
services or manage resources. Responsibilities are uniformly
distributed among machines in the system, known as peers, which
can serve as either client or server.
Example of a Distributed System
Distributed systems have endless use cases, a few being electronic
banking systems, massive multiplayer online games, and sensor
networks.
StackPath utilizes a particularly large distributed system to power its
content delivery network service. Every one of our points of presence
(PoPs) has nodes that form a worldwide distributed system. And to
provide top notch content delivery, StackPath stores the most recently
and frequently requested content in edge locations closest to the
location it is being used.
Goals of networking
The main goal of networking is "Resource sharing", and it is to
make all programs, data and equipment available to anyone on
the network without the regard to the physical location of the
resource and the user.

A second goal is to provide high reliability by having alternative
sources of supply. For example, all files could be replicated on two
or three machines, so if one of them is unavailable, the other
copies could be available.
Another goal is saving money. Small computers have a much
better price/performance ratio than larger ones. Mainframes are
roughly a factor of ten times faster than the fastest single chip
microprocessors, but they cost thousand times more. This
imbalance has caused many system designers to build systems
consisting of powerful personal computers, one per user, with
data kept on one or more shared file server machines. This goal
leads to networks with many computers located in the same
building. Such a network is called a LAN (local area network).
Another closely related goal is to increase the systems
performance as the work load increases by just adding more
processors. With central mainframes, when the system is full, it
must be replaced by a larger one, usually at great expense and
with even greater disruption to the users.
Computer networks provide a powerful communication medium.
A file that was updated or modified on a network can be seen by
the other users on the network immediately.

General approaches of communication
within a network & Network
classification
Communication Networks can be of following 5 types:
Local Area Network (LAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
Wireless
Inter Network (Internet)
Local Area Network (LAN)

It is also called LAN and designed for small physical areas such as an
office, group of buildings or a factory. LANs are used widely as it is easy
to design and to troubleshoot. Personal computers and workstations
are connected to each other through LANs. We can use different types
of topologies through LAN, these are Star, Ring, Bus, Tree etc.
LAN can be a simple network like connecting two computers, to share
files and network among each other while it can also be as complex as
interconnecting an entire building.
LAN networks are also widely used to share resources like printers,
shared hard-drive etc.
Characteristics of LAN
 LAN's are private networks, not subject to tariffs or other
regulatory controls.
 LAN's operate at relatively high speed when compared to the
typical WAN.

 There are different types of Media Access Control methods in a
LAN, the prominent ones are Ethernet, Token ring.
 It connects computers in a single building, block or campus, i.e.
they work in a restricted geographical area.
Applications of LAN
 One of the computer in a network can become a server serving all
the remaining computers called clients. Software can be stored on
the server and it can be used by the remaining clients.
 Connecting Locally all the workstations in a building to let them
communicate with each other locally without any internet access.
 Sharing common resources like printers etc are some common
applications of LAN.
Advantages of LAN
 Resource Sharing: Computer resources like printers, modems,
DVD-ROM drives and hard disks can be shared with the help of
local area networks. This reduces cost and hardware purchases.
 Software Applications Sharing: It is cheaper to use same software
over network instead of purchasing separate licensed software for
each client a network.
 Easy and Cheap Communication: Data and messages can easily be
transferred over networked computers.
 Centralized Data: The data of all network users can be saved on
hard disk of the server computer. This will help users to use any
workstation in a network to access their data. Because data is not
stored on workstations locally.

 Data Security: Since, data is stored on server computer centrally,
it will be easy to manage data at only one place and the data will
be more secure too.
 Internet Sharing: Local Area Network provides the facility to share
a single internet connection among all the LAN users. In Net
Cafes, single internet connection sharing system keeps the
internet expenses cheaper.
Disadvantages of LAN
 High Setup Cost: Although the LAN will save cost over time due to
shared computer resources, but the initial setup costs of installing
Local Area Networks is high.
 Privacy Violations: The LAN administrator has the rights to check
personal data files of each and every LAN user. Moreover he can
check the internet history and computer use history of the LAN
user.
 Data Security Threat: Unauthorised users can access important
data of an organization if centralized data repository is not
secured properly by the LAN administrator.
 LAN Maintenance Job: Local Area Network requires a LAN
Administrator because, there are problems of software
installations or hardware failures or cable disturbances in Local
Area Network. A LAN Administrator is needed at this full time job.
 Covers Limited Area: Local Area Network covers a small area like
one office, one building or a group of nearby buildings.
Metropolitan Area Network (MAN)

It was developed in 1980s.It is basically a bigger version of LAN. It is also
called MAN and uses the similar technology as LAN. It is designed to
extend over the entire city. It can be means to connecting a number of
LANs into a larger network or it can be a single cable. It is mainly hold
and operated by single private company or a public company.
Characteristics of MAN
 It generally covers towns and cities (50 km)
 Communication medium used for MAN are optical fibers, cables
etc.
 Data rates adequate for distributed computing applications.
Advantages of MAN
 Extremely efficient and provide fast communication via high-
speed carriers, such as fibre optic cables.
 It provides a good back bone for large network and provides
greater access to WANs.
 The dual bus used in MAN helps the transmission of data in both
directions simultaneously.

 A MAN usually encompasses several blocks of a city or an entire
city.
Disadvantages of MAN
 More cable required for a MAN connection from one place to
another.
 It is difficult to make the system secure from hackers and
industrial espionage(spying) graphical regions.
Wide Area Network (WAN)
It is also called WAN. WAN can be private or it can be public leased
network. It is used for the network that covers large distance such as
cover states of a country. It is not easy to design and maintain.
Communication medium used by WAN are PSTN or Satellite links. WAN
operates on low data rates.
Characteristics of WAN

 It generally covers large distances(states, countries, continents).
 Communication medium used are satellite, public telephone
networks which are connected by routers.
Advantages of WAN
 Covers a large geographical area so long distance business can
connect on the one network.
 Shares software and resources with connecting workstations.
 Messages can be sent very quickly to anyone else on the network.
These messages can have picture, sounds or data included with
them(called attachments).
 Expensive things(such as printers or phone lines to the internet)
can be shared by all the computers on the network without
having to buy a different peripheral for each computer.
 Everyone on the network can use the same data. This avoids
problems where some users may have older information than
others.
Disadvantages of WAN
 Need a good firewall to restrict outsiders from entering and
disrupting the network.
 Setting up a network can be an expensive, slow and complicated.
The bigger the network the more expensive it is.
 Once set up, maintaining a network is a full-time job which
requires network supervisors and technicians to be employed.
 Security is a real issue when many different people have the
ability to use information from other computers. Protection
against hackers and viruses adds more complexity and expense.

Wireless Network
Digital wireless communication is not a new idea. Earlier, Morse code
was used to implement wireless networks. Modern digital wireless
systems have better performance, but the basic idea is the same.
Wireless Networks can be divided into three main categories:
I. System interconnection
II. Wireless LANs
III. Wireless WANs
System Interconnection
System interconnection is all about interconnecting the components of
a computer using short-range radio. Some companies got together to
design a short-range wireless network called Bluetooth to connect
various components such as monitor, keyboard, mouse and printer, to
the main unit, without wires. Bluetooth also allows digital cameras,
headsets, scanners and other devices to connect to a computer by
merely being brought within range.
In simplest form, system interconnection networks use the master-
slave concept. The system unit is normally the master, talking to the
mouse, keyboard, etc. as slaves.

Wireless LANs
These are the systems in which every computer has a radio modem and
antenna with which it can communicate with other systems. Wireless
LANs are becoming increasingly common in small offices and homes,
where installing Ethernet is considered too much trouble. There is a
standard for wireless LANs called IEEE 802.11, which most systems
implement and which is becoming very widespread.
Wireless WANs
The radio network used for cellular telephones is an example of a low-
bandwidth wireless WAN. This system has already gone through three
generations.
 The first generation was analog and for voice only.
 The second generation was digital and for voice only.
 The third generation is digital and is for both voice and data.
Inter Network

Inter Network or Internet is a combination of two or more networks.
Inter network can be formed by joining two or more individual
networks by means of various devices such as routers, gateways and
bridges.

Uses & Network Software.
Had it not been of high importance, nobody would have bothered
connecting computers over a network. Let's start exploring the uses of
Computer Networks with some traditional usecases at companies and
for individuals and then move on to the recent developments in the
area of mobile users and home networking.
Network Software
Any software that interacts, increases and facilitates the functions of a
computer network is called network software. There are two basic
types of networking, the first type allows two computers to share, send
and receive data files via network while the second type of networking
allows shared access liberty to all the users and systems that are part of
the network.
A networking software has become an integral part of computer
networks as they facilitates the mode of communication and data
sharing. As a user, you must know how your computer network works
and all the devices that enables this networking to be efficient.

REFERENCE
http://www.steves-internet-guide.com/
https://www.stackpath.com/
https://www.ques10.com/
https://www.studytonight.com/
https://sites.google.com/site/cprorgrams/home
https://intellegensinc.com/

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Assignment 1