Networking

1. Shri Shivaji Science College, Amravati
Department of Computer Science
Topic- Basic elements of communication system (Unit I)
Prepared By
Dr. Ujwala S. Junghare
Assistant Professor
Dept. of Computer Science

2. What is Network?
 A network consists of two or more computers that are linked in order to share resources
(such as printers and CDs), exchange files, or allow electronic communications.
 Networking, also known as computer networking, is the practice of transporting and
exchanging data between nodes over a shared medium in an information system.
Networking comprises not only the design, construction and use of a network, but also
the management, maintenance and operation of the network infrastructure, software and
policies.
 The computers on a network may be linked through cables, telephone lines, radio
waves, satellites, or infrared light beams.
 Two very common types of networks include:
Local Area Network (LAN)
Wide Area Network (WAN)

3. Network concept
Types of networking
There are two primary types of computer networking: wired networking and wireless
networking.
Wired networking requires the use of a physical medium for transport between nodes.
Copper-based Ethernet cabling, popular due to its low cost and durability, is commonly
used for digital communications in businesses and homes. Alternatively, optical fiber is
used to transport data over greater distances and at faster speeds, but it has several
tradeoffs, including higher costs and more fragile components.
Wireless networking uses radio waves to transport data over the air, enabling devices to
be connected to a network without any cabling. Wireless LANs are the most well-known
and widely deployed form of wireless networking. Alternatives include microwave,
satellite, cellular and Bluetooth, among others.

4. Network example: your home Wi-Fi
 The Wireless LAN (Wireless Local Area Network, i.e. the Wi-Fi network) in your home
is a good example of a small client-server network. The various devices in your home
are wirelessly connected to the router, which acts as a central node (server) for the
household. The router itself is connected to a much larger network: the Internet.
 Since the devices are connected to the router as clients, they are part of the network and
can use the same resource as the server, namely the Internet. The devices can
also communicate with each other without having to establish a direct connection to
each device. For example, you can send a print job to a Wi-Fi-enabled printer without
first connecting the printer to the computer using a cable.
 Before the advent of modern networks, communication between different computers
and devices was very complicated. Computers were connected using a LAN cable.
Mechanical switches were used so that peripheral devices could also be shared. Due to
physical limitations (cable length), the devices and computers always had to be very
close to each other.

5. Advantages
These are main advantages of Computer Networks:
1. Central Storage of Data –
Files can be stored on a central node (the file server) that can be shared and made
available to each and every user in an organization.
2. Anyone can connect to a computer network –
There is a negligible range of abilities required to connect to a modern computer
network. The effortlessness of joining makes it workable for even youthful kids to start
exploiting the data.
3. Faster Problem solving –
Since an extensive procedure is disintegrated into a few littler procedures and each is
taken care of by all the associated gadgets, an explicit issue can be settled in lesser time.
4. Reliability –
Reliability implies backing up of information. Due to some reason equipment crash, and
so on, the information gets undermined or inaccessible on one PC, another duplicate of
similar information is accessible on another workstation for future use, which prompts
smooth working and further handling without interruption.

6. 5. It is highly flexible –
This innovation is known to be truly adaptable, as it offers clients the chance to
investigate everything about fundamental things, for example, programming without
influencing their usefulness.
6. Security through Authorization –
Security and protection of information is additionally settled through system. As just
the system clients are approved to get to specific records or applications, no other
individual can crack the protection or security of information.
7. It boosts storage capacity –
Since you will share data, records and assets to other individuals, you need to guarantee
all information and substance are legitimately put away in the framework. With this
systems administration innovation, you can do the majority of this with no issue, while
having all the space you requirement for capacity.

7. Disadvantages of Network:
These are main disadvantages of Computer Networks:
1. It lacks robustness –
If a PC system’s principle server separates, the whole framework would end up useless.
Also, if it has a bridging device or a central linking server that fails, the entire network
would also come to a standstill.
2. It lacks independence –
PC organizing includes a procedure that is worked utilizing PCs, so individuals will depend
a greater amount of PC work, rather than applying an exertion for their jobs that needs to be
done.
3. Virus and Malware –
On the off chance that even one PC on a system gets contaminated with an infection, there
is a possibility for alternate frameworks to get tainted as well. Infections can spread on a
system effectively, in view of the between availability of different gadgets.4. Lack of
Independence
4. Cost of network –
The expense of executing the system including cabling and equipment can be expensive.

8. Goals of Computer Network
The following are some important goals of computer networks:
1. Resource Sharing –
Many organization has a substantial number of computers in operations, which are located
apart. Ex. A group of office workers can share a common printer, fax, modem, scanner, etc.
2. High Reliability –
If there are alternate sources of supply, all files could be replicated on two or more machines. If
one of them is not available, due to hardware failure, the other copies could be used.
3. Inter-process Communication –
Network users, located geographically apart, may converse in an interactive session through
the network. In order to permit this, the network must provide almost error-free
communications.
4. Flexible access –
Files can be accessed from any computer in the network. The project can be begun on one
computer and finished on another. Other goals include Distribution of processing functions,
Centralized management, and allocation of network resources, Compatibility of dissimilar
equipment and software, Good network performance, Scalability, Saving money, Access to
remote information, Person to person communication, etc.

9. Network Topologies
 Network topology is the way a network is arranged, including the physical or logical
description of how links and nodes are set up to relate to each other.
 There are numerous ways a network can be arranged, all with different pros and cons,
and some are more useful in certain circumstances than others. Admins have a range of
options when it comes to choosing a network topology, and this decision must account
for the size and scale of their business, its goals, and budget. Several tasks go into
effective network topology management, including configuration management, visual
mapping, and general performance monitoring. The key is to understand your objectives
and requirements to create and manage the network topology in the right way for your
business.
 two categories in the network topology.
1. Physical – The physical network topology refers to the actual connections (wires, cables,
etc.) of how the network is arranged. Setup, maintenance, and provisioning tasks require
insight into the physical network.
2. Logical – The logical network topology is a higher-level idea of how the network is set
up, including which nodes connect to each other and in which ways, as well as how data
is transmitted through the network. Logical network topology includes any virtual and
cloud resources.

10. Type of Network Topology
 A star topology
 Ring,
 Completely connected N/W,
 Hybrid N/W,
 Multipoint n/w

11.  A star topology, the most common network topology, is laid out so every node
in the network is directly connected to one central hub via coaxial, twisted-pair,
or fiber-optic cable. Acting as a server, this central node manages data
transmission—as information sent from any node on the network has to pass
through the central one to reach its destination—and functions as a repeater,
which helps prevent data loss.

12. Advantages of Star Topology
Star topologies are common since they allow you to conveniently manage your entire network from a
single location. Because each of the nodes is independently connected to the central hub, should one
go down, the rest of the network will continue functioning unaffected, making the star topology a
stable and secure network layout.
Additionally, devices can be added, removed, and modified without taking the entire network offline.
On the physical side of things, the structure of the star topology uses relatively little cabling to fully
connect the network, which allows for both straightforward setup and management over time as the
network expands or contracts. The simplicity of the network design makes life easier for
administrators, too, because it’s easy to identify where errors or performance issues are occurring.
Disadvantages of Star Topology
On the flipside, if the central hub goes down, the rest of the network can’t function. But if the central
hub is properly managed and kept in good health, administrators shouldn’t have too many issues.
The overall bandwidth and performance of the network are also limited by the central node’s
configurations and technical specifications, making star topologies expensive to set up and operate.

13. Ring Topology: Single vs. Dual
 Ring topology is where nodes are arranged in a circle (or ring). The data can travel
through the ring network in either one direction or both directions, with each device
having exactly two neighbors.
Advantages of Ring Topology
Since each device is only connected to the ones on either side, when data is transmitted, the
packets also travel along the circle, moving through each of the intermediate nodes until
they arrive at their destination. If a large network is arranged in a ring topology, repeaters
can be used to ensure packets arrive correctly and without data loss.

14.  Only one station on the network is permitted to send data at a time, which greatly reduces
the risk of packet collisions, making ring topologies efficient at transmitting data without
errors.
 By and large, ring topologies are cost-effective and inexpensive to install, and the intricate
point-to-point connectivity of the nodes makes it relatively easy to identify issues or
misconfigurations on the network.
Disadvantages of Ring Topology
 Even though it’s popular, a ring topology is still vulnerable to failure without proper
network management. Since the flow of data transmission moves unidirectionally between
nodes along each ring, if one node goes down, it can take the entire network with it. That’s
why it’s imperative for each of the nodes to be monitored and kept in good health.
Nevertheless, even if you’re vigilant and attentive to node performance, your network can
still be taken down by a transmission line failure.
 The question of scalability should also be taken into consideration. In a ring topology, all
the devices on the network share bandwidth, so the addition of more devices can contribute
to overall communication delays. Network administrators need to be mindful of the devices
added to the topology to avoid overburdening the network’s resources and capacity.
 Additionally, the entire network must be taken offline to reconfigure, add, or remove
nodes. And while that’s not the end of the world, scheduling downtime for the network can
be inconvenient and costly.

15. Dual-Ring Topology:
 A network with ring topology is half-duplex, meaning data can only move in one direction at
a time. Ring topologies can be made full-duplex by adding a second connection between
network nodes, creating a dual ring topology.
Advantages of Dual-Ring Topology
The primary advantage of dual ring topology is its efficiency: because each node has two
connections on either side, information can be sent both clockwise and counterclockwise
along the network. The secondary ring included in a dual-ring topology setup can act as a
redundant layer and backup, which helps solve for many of the disadvantages of traditional
ring topology. Dual ring topologies offer a little extra security, too: if one ring fails within a

16. Fully connected network (Full Connected Mesh Topology)
In this topology, every nodes or device are directly connected with each other.
In a fully connected network, all nodes are interconnected. (In graph theory this is
called a complete graph.) The simplest fully connected network is a two-node
network. A fully connected network doesn't need to use packet
switching or broadcasting. However, since the number of connections grows
quadratically with the number of nodes:
This makes it impractical for large networks. This kind of topology does not trip and
affect other nodes in the network.

17. Disadvantages:
•Installation is complex because every node is connected to every node.
•Dedicated links help you to eliminate the traffic problem.
•A mesh topology is robust.
•Every system has its privacy and security
•It is expensive due to the use of more cables. No proper utilization of
systems.
•It requires more space for dedicated links.
•Because of the amount of cabling and the number of input-outputs, it is
expensive to implement.
•It requires a large space to run the cables.
Advantages:
Here, are pros/benefits of Mesh topology
•The network can be expanded without disrupting current users.
•Need extra capable compared with other LAN topologies.
•Complicated implementation.
•No traffic problem as nodes has dedicated links.
•It has multiple links, so if any single route is blocked, then other routes should be used for data
communication.
•P2P links make the fault identification isolation process easy.
•It helps you to avoid the chances of network failure by connecting all the systems to a central
node.

18. Hybrid Topology
Hybrid topology is a mixture of two or more topologies. It inherits the pros and cons of all
using topologies in the network.
Hybrid topologies are reliable. Error detection and correction is easy in such networks.
These are effective and flexible topologies that can easily be scaled according to the size of
area.

19. Multipoint Topology:
Multipoint topology is based on “sharing”. In this type of topology, each node on a network has
only one connection. Bus Topology is a common example of Multipoint Topology.
Bus Topology
In case of Bus topology, all devices share single communication line or cable. Bus topology
may have problem while multiple hosts sending data at the same time. Therefore, Bus
topology either uses CSMA/CD technology or recognizes one host as Bus Master to solve the
issue. It is one of the simple forms of networking where a failure of a device does not affect
the other devices. But failure of the shared communication line can make all other devices
stop functioning.
Both ends of the shared channel have line terminator. The data is sent in only one direction
and as soon as it reaches the extreme end, the terminator removes the data from the line.

20. Advantages of Bus Topology :
It is the easiest network topology for connecting peripherals or computers in a linear fashion.
It works very efficient well when there is a small network.
Length of cable required is less than a star topology.
It is easy to connect or remove devices in this network without affecting any other device.
Very cost-effective as compared to other network topology i.e. mesh and star
It is easy to understand topology.
Easy to expand by joining the two cables together.
Disadvantages of Bus Topology :
Bus topology is not great for large networks.
Identification of problem becomes difficult if whole network goes down.
Troubleshooting of individual device issues is very hard.
Need of terminators are required at both ends of main cable.
Additional devices slow network down.
If a main cable is damaged, whole network fails or splits into two.
Packet loss is high.
This network topology is very slow as compared to other topologies.

21. LAN (local area network)
A local area network (LAN) is a collection of devices connected together in one physical location,
such as a building, office, or home. A LAN can be small or large, ranging from a home network
with one user to an enterprise network with thousands of users and devices in an office or school.
Regardless of size, a LAN's single defining characteristic is that it connects devices that are in a
single, limited area. In contrast, a wide area network (WAN) or metropolitan area network (MAN)
covers larger geographic areas. Some WANs and MANs connect many LANs together.
A LAN comprises cables, access points, switches, routers, and other components that enable
devices to connect to internal servers, web servers, and other LANs via wide area networks.
The rise of virtualization has also fueled the development of virtual LANs, which enable network
administrators to logically group network nodes and partition their networks without a need for
major infrastructure changes.
For example, in an office with multiple departments, such as accounting, IT support, and
administration, each department's computers could be logically connected to the same switch but
segmented to behave as if they are separate.

22. Characteristics of LAN
Here are important characteristics of a LAN network:
It is a private network, so an outside regulatory body never controls it.
LAN operates at a relatively higher speed compared to other WAN systems.
There are various kinds of media access control methods like token ring and ethernet.
Advantages of LAN
Here are pros/benefits of using LAN:
LANs were developed in the 1960s for use by colleges, universities, and research facilities (such as NASA), primarily to
connect computers to other computers. It wasn't until the development of Ethernet technology (1973, at Xerox PARC), its
commercialization (1980), and its standardization (1983) that LANs started to be used widely.
Computer resources like hard-disks, DVD-ROM, and printers can share local area networks. This significantly reduces the
cost of hardware purchases.
You can use the same software over the network instead of purchasing the licensed software for each client in the network.
Data of all network users can be stored on a single hard disk of the server computer.
You can easily transfer data and messages over networked computers.
It will be easy to manage data at only one place, which makes data more secure.
Local Area Network offers the facility to share a single internet connection among all the LAN users.

24. Disadvantages of LAN
Here are the important cons/ drawbacks of LAN:
LAN will indeed save cost because of shared computer resources, but the initial cost of
installing Local Area Networks is quite high.
The LAN admin can check personal data files of every LAN user, so it does not offer
good privacy.
Unauthorized users can access critical data of an organization in case LAN admin is not
able to secure centralized data repository.
Local Area Network requires a constant LAN administration as there are issues related
to software setup and hardware failures

25. In general, there are two types of LANs: client/server LANs and peer-to-peer LANs.
A client/server LAN consists of several devices (the clients) connected to a central server. The
server manages file storage, application access, device access, and network traffic. A client
can be any connected device that runs or accesses applications or the Internet. The clients
connect to the server either with cables or through wireless connections.
Typically, suites of applications can be kept on the LAN server. Users can access databases,
email, document sharing, printing, and other services through applications running on the
LAN server, with read and write access maintained by a network or IT administrator. Most
midsize to large business, government, research, and education networks are client/server-
based LANs.
A peer-to-peer LAN doesn't have a central server and cannot handle heavy workloads like a
client/server LAN can, and so they're typically smaller. On a peer-to-peer LAN, each device
shares equally in the functioning of the network. The devices share resources and data
through wired or wireless connections to a switch or router. Most home networks are peer-to-
peer.

26. WAN (Wide Area Network) is another important computer network that which is spread across a large geographical area.
WAN network system could be a connection of a LAN which connects with other LAN's using telephone lines and radio
waves. It is mostly limited to an enterprise or an organization.
In its simplest form, a wide-area network (WAN) is a collection of local-area networks (LANs) or other networks that
communicate with one another. A WAN is essentially a network of networks, with the Internet the world's largest WAN.
Today, there are several types of WANs, built for a variety of use cases that touch virtually every aspect of modern life
WAN (Wide Area Network)
Characteristics of WAN:
The software files will be shared among all the users; therefore, all can access to the latest files.
Any organization can form its global integrated network using WAN.

27. Advantages of WAN
Here are the benefits/ pros of using WAN:
WAN helps you to cover a larger geographical area. Therefore business offices situated at longer
distances can easily communicate.
Contains devices like mobile phones, laptop, tablet, computers, gaming consoles, etc.
WLAN connections work using radio transmitters and receivers built into client devices.
Disadvantage of WAN
Here are drawbacks/cons of using WAN:
The initial setup cost of investment is very high.
It is difficult to maintain the WAN network. You need skilled technicians and network
administrators.
There are more errors and issues because of the wide coverage and the use of different
technologies.
It requires more time to resolve issues because of the involvement of multiple wired and wireless
technologies.
Offers lower security compared to other types of networks.

28. OSI Model
The OSI Model (Open Systems Interconnection Model) is a conceptual framework used to describe the
functions of a networking system. The OSI model characterizes computing functions into a universal set of
rules and requirements in order to support interoperability between different products and software. In the
OSI reference model, the communications between a computing system are split into seven different
abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
Created at a time when network computing was in its infancy, the OSI was published in 1984 by the
International Organization for Standardization (ISO). Though it does not always map directly to specific
systems, the OSI Model is still used today as a means to describe Network Architecture.

29. Physical Layer
The lowest layer of the OSI Model is concerned with electrically or optically transmitting raw unstructured
data bits across the network from the physical layer of the sending device to the physical layer of the
receiving device. It can include specifications such as voltages, pin layout, cabling, and radio frequencies.
At the physical layer, one might find “physical” resources such as network hubs, cabling, repeaters,
network adapters or modems.
Data Link Layer
At the data link layer, directly connected nodes are used to perform node-to-node data transfer where data
is packaged into frames. The data link layer also corrects errors that may have occurred at the physical
layer.
The data link layer encompasses two sub-layers of its own. The first, media access control (MAC),
provides flow control and multiplexing for device transmissions over a network. The second, the logical
link control (LLC), provides flow and error control over the physical medium as well as identifies line
protocols.

30. Network Layer
The network layer is responsible for receiving frames from the data link layer, and delivering
them to their intended destinations among based on the addresses contained inside the frame.
The network layer finds the destination by using logical addresses, such as IP (internet
protocol). At this layer, routers are a crucial component used to quite literally route
information where it needs to go between networks.
Transport Layer
The transport layer manages the delivery and error checking of data packets. It regulates the
size, sequencing, and ultimately the transfer of data between systems and hosts. One of the
most common examples of the transport layer is TCP or the Transmission Control Protocol.
Session Layer
The session layer controls the conversations between different computers. A session or
connection between machines is set up, managed, and termined at layer 5. Session layer
services also include authentication and reconnections.

31. Presentation Layer
The presentation layer formats or translates data for the application layer based on the syntax or
semantics that the application accepts. Because of this, it at times also called the syntax layer. This
layer can also handle the encryption and decryption required by the application layer.
Application Layer
At this layer, both the end user and the application layer interact directly with the software
application. This layer sees network services provided to end-user applications such as a web
browser or Office 365. The application layer identifies communication partners, resource
availability, and synchronizes communication.