NETWORK AND SECURITY-Dr.Poovendran R.pptx

NETWORK AND SECURITY
Dr.Poovendran R
IT professional

NETWORKS
What is Network?
A computer network is a cluster of computers over a shared
communication path that works to share resources from one
computer to another, provided by or located on the network
nodes.
• Uses of Computer Networks
• Communicating using email, video, instant messaging, etc.
• Sharing devices such as printers, scanners, etc.
• Sharing files.
• Sharing software and operating programs on remote
systems.
• Allowing network users to easily access and maintain
information.

Basic Terminologies in Networks
• Network: A network is a collection of computers and devices that are
connected together to enable communication and data exchange.
• Nodes: Nodes are devices that are connected to a network. These can
include computers, Servers, Printers, Routers, Switches, and other
devices.
• Protocol: A protocol is a set of rules and standards that govern how data
is transmitted over a network. Examples of protocols include TCP/IP, HTTP,
and FTP.
• Topology: Network topology refers to the physical and logical
arrangement of nodes on a network. The common network topologies
include bus, star, ring, mesh, and tree.

Basic terminologies in networks
• Service Provider Networks: These types of Networks give permission
to take Network Capacity and Functionality on lease from the
Provider. Service Provider Networks include Wireless
Communications, Data Carriers, etc.
• IP Address: An IP address is a unique numerical identifier that is
assigned to every device on a network. IP addresses are used to
identify devices and enable communication between them.
• DNS: The Domain Name System (DNS) is a protocol that is used to
translate human-readable domain names (such as www.google.com)
into IP addresses that computers can understand.

Basic terminologies in networks
• Firewall: A firewall is a security device that is used to monitor and
control incoming and outgoing network traffic. Firewalls are used to
protect networks from unauthorized access and other security
threats.

Types of area networks
• The Network allows computers to connect and communicate with
different computers via any medium. LAN, MAN, and WAN are the
three major types of networks designed to operate over the area they
cover. There are some similarities and dissimilarities between them.
One of the major differences is the geographical area they cover, i.e.
LAN covers the smallest area, MAN covers an area larger than LAN
and WAN comprises the largest of all.

Types of area networks
There are four main types of area networks as follows:
• Personal Area Network (PAN)
• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)

Personal Area Network
(PAN)
• PAN is a personal area network having an
interconnection of personal technology devices to
communicate over a short distance. It covers only
less than 10 meters or 33 feet of area. PAN has
fewer users as compared to other networks such
as LAN, WAN, etc. PAN typically uses some form
of wireless technology. PAN involves the
transmission of data between information
devices such as smartphones, personal
computers, tablet computers, etc.

Local area network
(LAN)
• LAN or Local Area Network connects network
devices in such a way that personal computers
and workstations can share data, tools, and
programs. The group of computers and devices
are connected together by a switch, or stack of
switches, using a private addressing scheme as
defined by the TCP/IP protocol. Private addresses
are unique in relation to other computers on the
local network. Routers are found at the boundary
of a LAN, connecting them to the larger WAN.

Metropolitian Area
Network (MAN)
• MAN or Metropolitan area Network covers a larger area
than that covered by a LAN and a smaller area as compared
to WAN. MAN has a range of 5-50km. It connects two or
more computers that are apart but reside in the same or
different cities. It covers a large geographical area and may
serve as an ISP (Internet Service Provider). MAN is
designed for customers who need high-speed connectivity.
Speeds of MAN range in terms of Mbps. It’s hard to design
and maintain a Metropolitan Area Network.

Wide Area Network
(WAN)
• WAN or Wide Area Network is a computer
network that extends over a large geographical
area, although it might be confined within the
bounds of a state or country. WAN has a range
of above 50 km. A WAN could be a connection
of LAN connecting to other LANs via telephone
lines and radio waves and may be limited to an
enterprise (a corporation or an organization)
or accessible to the public. The technology is
high-speed and relatively expensive.

Components Used in Computer Networking
• The hardware and software needed to set up computer networks at homes and
businesses are referred to as computer network components.
• The server, client, peer, transmission media, and connecting devices make up
the hardware components.
• The operating system and protocols are examples of software components.
Basically, a computer network is made up of several computers connected to
one another so that resources and data can be shared.
• Wireless or cable-based media are used to connect many PCs.

Types of Physical Components used in
Computer Networking
• NIC(Network Interface Card)
• HUB
• Router
• Modem
• Switch
• Nodes
• Media
• Repeater
• Server

NIC(Network Interface Card)
• NIC or network interface card is a network
adapter used to connect the computer to the
network. It is installed in the computer to
establish a LAN. It has a unique ID that is
written on the chip, and it has a connector to
connect the cable to it. The cable acts as an
interface between the computer and the router
or modem. NIC card is a layer 2 device, which
means it works on the network model’s physical
and data link layers.
Types of NIC
• Wired NIC: Cables and Connectors use Wired
NIC to transfer data.
• Wireless NIC: These connect to a wireless
network such as Wi-Fi, Bluetooth, etc

HUB
A HUB is a multi-port repeater. Hubs cannot
filter data, so data packets are sent to all
connected devices. In other words, the
collision domain of all hosts connected
through Hub remains one.
.

SWITCH
• A Switch is a multiport bridge with a buffer and
a design that can boost its efficiency(a large
number of ports implies less traffic) and
performance.
• A switch is a data link layer device. The switch
can perform error checking before forwarding
data, which makes it very efficient as it does
not forward packets that have errors and
forward good packets selectively to the correct
port only.

Modem
• A Modem is a short form of
Modulator/Demodulator. The Modem is a
hardware component/device that can connect
computers and other devices such as routers
and switches to the internet. Modems convert
or modulate the analog signals coming from
telephone wire into a digital form that is in the
form of 0s and 1s.

Router
A Router is a device like a switch that routes
data packets based on their IP addresses. The
router is mainly a Network Layer device.
Routers normally connect LANs and WANs and
have a dynamically updating routing table
based on which they make decisions on routing
the data packets. The router divides the
broadcast domains of hosts connected through
it.

Repeater
• Repeater is an important component of computer
networks as it is used to regenerate and amplify
signal in the computer networks. Repeaters are
used to improve the quality of the networks and
they are operated on the Physical Layer of the OSI
Model.

Server
A server is a computer program that provides
various functionality to another computer program.
The server plays a vital role in facilitating
communication, data storage, etc.
Servers have more data storage as compared to
normal computers. They are designed for the
specific purpose of handling multiple requests from
clients.

Media
• It is also known as Link which is going to carry
data from one side to another side. This link
can be Wired Medium (Guided Medium) and
Wireless Medium (Unguided Medium). It is of
two types:
1. Wired Media
2. Wireless Media
• Examples of Wired media are as follows:
• Ethernet: Ethernet is the most widely used
LAN technology, which is defined under IEEE
standards 802.3. There are two types of
Ethernet:
1. Ethernet straight-through cable (used for
two different devices).
2. Ethernet crossover cable (used for two same
devices). 45g

Types of wired cable media
• Fiber Optic Cable: In this data is
transferred in the form of light waves.
• Coaxial Cable: Mainly used for audio
and video communications.
• USB Cable: USB Stands for Universal
Serial Bus. Mainly used to connect PCs
and smartphones.

OSI Layers in networking
• OSI stands for Open Systems Interconnection, where open stands to say
non-proprietary. It is a 7-layer architecture with each layer having
specific functionality to perform. All these 7 layers work collaboratively
to transmit the data from one person to another across the globe.
• The OSI reference model was developed by ISO – ‘International
Organization for Standardization‘, in the year 1984.

7 Layers of OSI Model
The OSIs Model, or Open Systems Interconnection,

Comparison of the 7 Layers of OSI Model
Purpose and Functions Hardware Devices & Protocols Common Problems
OSI Layer 1: Physical
Data’s physical and electrical transmission
over a network connection
Network cards, hubs, switches,
routers, etc. Protocols include
Ethernet and PPP
Faulty connections between two
nodes, inadequate bandwidth
OSI Layer 2: Data Link
Providing reliable link-level data transfer
between two nodes
Network cards, hubs, switches,
routers, etc. Protocols used
include Ethernet and PPP
Misconfigured or incompatible
hardware devices, protocol
mismatch errors
OSI Layer 3: Network
Routing packets from the source to the
destination
Network cards, routers, and
gateways. Protocols used include
IP, ICMP, ARP, OSPF, BGP, etc
Inefficient path selection
algorithms, incorrect data format
or incorrect routing information
OSI Layer 4: Transport
Providing reliable end-to-end communication
between two nodes in a network
TCP and UDP
Inefficient path selection
algorithms, incorrect data format
OSI Layer 5: Session
Establishing and maintaining a session
between two applications
SNMP, Telnet, and RPC
Missing or corrupted session data
OSI Layer 6:
Presentation
Converting data between different formats
and ensuring end-to-end data integrity
SSL/TLS, S-HTTP, and SSH
Conversions errors caused by
incorrect data format or coding
errors
OSI Layer 7:
Application
Responsible for providing end-user services,
such as file transfer, web browsing, email,
and chat.
Network cards, servers,
HTTP, FTP, SMTP, and SSL/TLS
Misconfigured routers or
gateways, inadequate bandwidth,
signal interference due to
electrical noise or radio waves

FUNCTIONS OF PHYSICAL LAYER
Bit synchronization: The physical layer
provides the synchronization of the bits
by providing a clock. This clock controls
both sender and receiver thus providing
synchronization at the bit level.
Bit rate control: The Physical layer also
defines the transmission rate i.e. the
number of bits sent per second.
Physical topologies: Physical layer
specifies how the different,
devices/nodes are arranged in a
network i.e. bus, star, or mesh topology.
Transmission mode: Physical layer also
defines how the data flows between the
two connected devices. The various
transmission modes possible are
Simplex, half-duplex and full-duplex.
Hub, Repeater, Modem, and Cables are Physical Layer devices.

DATA LINK LAYER
• The data link layer is responsible for the node-to-node delivery of the
message. The main function of this layer is to make sure data transfer
is error-free from one node to another, over the physical layer. When
a packet arrives in a network, it is the responsibility of the DLL to
transmit it to the Host using its MAC address.
• The Data Link Layer is divided into two sublayers:
• Logical Link Control (LLC)
• Media Access Control (MAC)

FUNCTIONS OF DATALINK LAYER
• Framing: Framing is a function of the data link layer. It provides a way for a sender to
transmit a set of bits that are meaningful to the receiver. This can be accomplished by
attaching special bit patterns to the beginning and end of the frame.
• Physical addressing: After creating frames, the Data link layer adds physical addresses
(MAC addresses) of the sender and/or receiver in the header of each frame.
• Error control: The data link layer provides the mechanism of error control in which it
detects and retransmits damaged or lost frames.
• Flow Control: The data rate must be constant on both sides else the data may get
corrupted thus, flow control coordinates the amount of data that can be sent before
receiving an acknowledgment.
• Access control: When a single communication channel is shared by multiple devices, the
MAC sub-layer of the data link layer helps to determine which device has control over
the channel at a given time.
• Switch & Bridge are Data Link Layer devices.

NETWORK LAYER
• The network layer works for the transmission of data from one host to the other located in
different networks. It also takes care of packet routing i.e. selection of the shortest path to
transmit the packet, from the number of routes available. The sender & receiver’s IP addresses
are placed in the header by the network layer.
Functions of the Network Layer
• Routing: The network layer protocols determine which route is suitable from source to
destination. This function of the network layer is known as routing.
• Logical Addressing: To identify each device inter-network uniquely, the network layer defines an
addressing scheme. The sender & receiver’s IP addresses are placed in the header by the network
layer. Such an address distinguishes each device uniquely and universally.

TRANSPORT LAYER
• The transport layer provides services to the application layer and takes services
from the network layer. The data in the transport layer is referred to as Segments.
It is responsible for the end-to-end delivery of the complete message. The
transport layer also provides the acknowledgment of the successful data
transmission and re-transmits the data if an error is found.
• At the sender’s side: The transport layer receives the formatted data from the
upper layers, performs Segmentation, and also implements Flow and error
control to ensure proper data transmission. It also adds Source and Destination
port numbers in its header and forwards the segmented data to the Network
Layer.

FUNCTIONS OF TRANSPORT LAYER
• Segmentation and Reassembly: This layer accepts the message from
the (session) layer, and breaks the message into smaller units. Each of
the segments produced has a header associated with it. The transport
layer at the destination station reassembles the message.
• Service Point Addressing: To deliver the message to the correct
process, the transport layer header includes a type of address called
service point address or port address. Thus by specifying this address,
the transport layer makes sure that the message is delivered to the
correct process.

SESSION LAYER
• This layer is responsible for the establishment of connection, maintenance
of sessions, and authentication, and also ensures security.
Functions of the Session Layer
• Session establishment, maintenance, and termination: The layer allows the
two processes to establish, use, and terminate a connection.
• Synchronization: This layer allows a process to add checkpoints that are
considered synchronization points in the data. These synchronization
points help to identify the error so that the data is re-synchronized
properly, and ends of the messages are not cut prematurely and data loss is
avoided.
• Dialog Controller: The session layer allows two systems to start
communication with each other in half-duplex or full-duplex.

PRESENTATION LAYER
• The presentation layer is also called the Translation layer. The data from the
application layer is extracted here and manipulated as per the required format
to transmit over the network.
Functions of the Presentation Layer
• Translation: For example, ASCII to EBCDIC.
• Encryption/ Decryption: Data encryption translates the data into another form
or code. The encrypted data is known as the ciphertext and the decrypted
data is known as plain text. A key value is used for encrypting as well as
decrypting data.
• Compression: Reduces the number of bits that need to be transmitted on the
network.

APPLICATION LAYER
• At the very top of the OSI Reference Model stack of layers, we find
the Application layer which is implemented by the network
applications. These applications produce the data to be transferred
over the network. This layer also serves as a window for the
application services to access the network and for displaying the
received information to the user.
• Example: Application – Browsers, Skype Messenger, etc.

Transmission Control Protocol/Internet Protocol. The TCP/IP
model
What Does TCP/IP Do?
The main work of TCP/IP is to transfer the data of a computer from one device to another. The main condition of
this process is to make data reliable and accurate so that the receiver will receive the same information which is
sent by the sender.
What is the Difference between TCP and IP?
TCP and IP are different protocols of Computer Networks. The basic difference between TCP (Transmission
Control Protocol) and IP (Internet Protocol) is in the transmission of data. In simple words, IP finds the
destination of the mail and TCP has the work to send and receive the mail.
How Does the TCP/IP Model Work?
Whenever we want to send something over the internet using the TCP/IP Model, the TCP/IP Model divides the
data into packets at the sender’s end and the same packets have to be recombined at the receiver’s end to form
the same data, and this thing happens to maintain the accuracy of the data.

Ethernet
Ethernet is the traditional technology for connecting devices in a wired local area
network (LAN) or wide area network. It enables devices to communicate with each
other via a protocol, which is a set of rules
Ethernet describes how network devices format and transmit data so other devices on
the same LAN or campus network can recognize, receive and process the information.
An Ethernet cable is the physical, encased wiring over which the data travels
Types of Ethernet cables
The IEEE 802.3 Working Group approved the first Ethernet standard in 1983. Since
then, the technology
Classic Ethernet is the original form of Ethernet that provides data rates between 3 to 10
Mbps.

WLAN
WLAN stands for Wireless Local Area Network. WLAN is a local area
network that uses radio communication to provide mobility to the network
users while maintaining the connectivity to the wired network. A WLAN
basically, extends a wired local area network. WLAN’s are built by attaching a
device called the access point(AP) to the edge of the wired network.

Bluetooth
Bluetooth is used for short-range wireless voice and data communication. It is a Wireless Personal Area
Network (WPAN) technology and is used for data communications over smaller distances.
Bands from 2.4 GHz to 2.485 GHz. Bluetooth stages up to 10 meters. Depending upon the version, it
presents information up to at least 1 Mbps or 3 Mbps.
Key Features of Bluetooth
•The transmission capacity of Bluetooth is 720 kbps.
•Bluetooth is a wireless device.
•Bluetooth is a Low-cost and short-distance radio communications standard.
•Bluetooth is robust and flexible.

High-level Data Link Control (HDLC) and Point-to-Point Protocol
(PPP)
The main difference between High-level Data Link Control (HDLC) and Point-to-Point Protocol (PPP) is
that High-level Data Link Control is the bit-oriented protocol, on the other hand, Point-to-Point Protocol is the
byte-oriented protocol
Features of HDLC:
•Error detection and correction: HDLC uses error detection and correction mechanisms such as CRCs and
acknowledgments to ensure the integrity of the transmitted data.
•Full-duplex communication.
•Multiplexing:
•Features of PPP:
•Authentication: PPP includes authentication mechanisms such as Password Authentication Protocol (PAP) and
Challenge Handshake Authentication Protocol.
•Error detection and correction: PPP uses error detection and correction mechanisms such as CRCs and
acknowledgments to ensure the integrity of the transmitted data.

What is IP Addressing?
• An IP address represents an Internet Protocol address. A unique address
that identifies the device over the network. It is almost like a set of rules
governing the structure of data sent over the Internet or through a local
network.
• An IP address helps the Internet to distinguish between different
routers, computers, and websites.
• It serves as a specific machine identifier in a specific network and helps
to improve visual communication between source and destination

IP Addressing
• 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.
• the full IP addressing range goes from 0.0.0.0 to 255.255.255.255.
• Private IP addresses
• Public IP addresses

Internet Protocol
• Parts of IP
• Network part:
The network part indicates the distinctive variety that’s appointed to
the network. The network part conjointly identifies the category of
the network that’s assigned.
• Host Part:
The host part uniquely identifies the machine on your network. This
part of the IPv4 address is assigned to every host.
For each host on the network, the network part is the same, however,
the host half must vary.

Network layer protocols
Every computer in a network has an IP address by which it can be uniquely identified and
addressed. An IP address is Layer-3 (Network Layer) logical address
Below are some of the types of Network protocols:
•Transmission Control Protocol (TCP) ...
•Internet Protocol (IP) ...
•Hypertext Transfer Protocol (HTTP) ...
•Simple Mail Transfer Protocol (SMTP) ...
•Post Office Protocol (POP) and Internet Message Access Protocol (IMAP) ...
•File Transfer Protocol (FTP) ---

Internet Protocol Version 4 (IPv4)
IPv4 is 32-bit addressing scheme used as TCP/IP host addressing mechanism. IP
addressing enables every host on the TCP/IP network to be uniquely identifiable.
8.8.8.8
•Class A - it uses first octet for network addresses and last
•Class B - it uses first two octets for network addresses and last two for host addressing
•Class C - it uses first three octets for network addresses and last one for host
addressing
•Class D - it provides flat IP addressing scheme in contrast to hierarchical structure for
above three.
•Class E - It is used as experimental.
•Classless Inter-Domain Routing (CIDR)

Intra domain is any protocol in which Routing algorithm works only within domains
on the other hand Inter domain is any protocol in which Routing algorithm works
within and between domains
S.No Intradomain Routing Interdomain Routing
1. Routing algorithm works only within domains.
Routing algorithm works within and
between domains.
2.
It need to know only about other routers within their
domain.
It need to know only about other
routers within and between their
domain.
3.
Protocols used in intradomain routing are known
as Interior-gateway protocols.
Protocols used in interdomain routing
are known as Exterior-gateway
protocols.
4.
In this Routing, routing takes place within an
autonomous network.
In this Routing, routing takes place
between the autonomous networks.

Network Layer is responsible for the transmission of data or communication from one
host to another host connected in a network
IPv4 is responsible for packetizing, forwarding, and delivery of a packet.
Functions of Network Layer
Logical Addressing: Each device on the network needs to be identified uniquely.
Therefore network layer provides an addressing scheme to identify the device. It places
the IP address of every sender and the receiver in the header. This header consists of the
network ID and host ID of the network.
Host-to-host Delivery of Data
Fragmentation:
Routing and Forwarding

Routing and Forwarding

IP (Internet Protocol)
IP stands for Internet Protocol. Internet Protocol helps to uniquely identify each device
on the network. Internet protocol is responsible for transferring the data from one node
to another node in the network. Internet protocol is a connectionless protocol therefore
it does not guarantee the delivery of data. For the successful delivery higher level
protocols such as TCP are used to guarantee the data transmission.
IPv4: IPv4 provides with the 32 bit address scheme
IPv6: IPv6 is the most recent version of IP. If provided with a 128 but addressing
scheme.
ARP (Address Resolution Protocol)
ARP stands for Address Resolution Protocol. ARP is used to convert the logical address
ie. IP address into physical address ie. MAC -address. While communicating with other
nodes, it is necessary to know the MAC address or physical address of the destination
node.

Network layer protocols Cont…
ICMP
ICMP stands for Internet Control Message Protocol. ICMP is a part of IP protocol suite.
ICMP is an error reporting and network diagnostic protocol. Feedback in the network is
reported to the designated host. Meanwhile, if any kind of error occur it is then reported
to ICMP.
The ICMP message is of 32 bit. It consists of 3 fields. First field is of 8 bit that states type
of message, second field is of 8 bit that states the reason of message and the third field is
of 16 but that consists of actual ICMP message.
The messages in ICMP are divided into two types. They are given below:
•Error Message: Error message states about the issues or problems that are faced by the
host or routers during processing of IP packet.
•Query Message: Query messages are used by the host in order to get information from a
router or another host.

IGMP
• IGMP stands for Internet Group Message Protocol. ICMP is a multicasting
communication protocol. It utilizes the resources efficiently while broadcasting the
messages and data packets.
• Mobile Internet Protocol (or Mobile IP)
• Mobile IP is a communication protocol (created by extending Internet Protocol, IP)
that allows the users to move from one network to another with the same IP address.
It ensures that the communication will continue without the user’s sessions or
connections being dropped.
• Mobile IP is a communication protocol (created by extending Internet Protocol, IP)
that allows the users to move from one network to another with the same IP address.
It ensures that the communication will continue without the user’s sessions or
connections being dropped.

Unicast and Multicast Routing
• Unicast : Unicast is a type of information transfer and it is used when there is
a participation of single sender and single recipient. So, in short, you can term
it as a one-to-one mapping.
• For example, a device having IP address 10.1.4.0 in a network wants to send
the traffic stream (data packets) to the device with IP address 20.14.4.2 in the
other network, then unicast comes into the picture. It is the most common form
of data transfer over the networks.
•

• Multicasting : Multicasting has one/more senders and multiple recipients participate in
data transfer traffic. In multicasting traffic recline between the boundaries of unicast
and broadcast. It server’s direct single copies of data streams and that are then
simulated and routed to hosts that request it. IP multicast requires support of some other
protocols such as Internet Group

Difference between Unicast and Multicast :
S.No. Unicast Multicast
1. It has one sender and one receiver.
It has one or more senders and
multiple receivers.
2.
It sends data from one device to
single device.
It sends data from one device to
multiple devices.
3. It works on Single Node Topology.
It works on star, mesh, tree and
hybrid topology.
4.
It does not scale well for streaming
media.
It does not scale well across large
networks.
5.
Multiple unicasting utilizes more
bandwidth as compared.
It utilizes bandwidth efficiently.

IPV6 Addresses Internet Protocol version
• IPv6 was developed by Internet Engineering Task Force (IETF) to deal with the problem
of IPv4 exhaustion. IPv6 is a 128-bits address having an address space of 2128, which is
way bigger than IPv4. IPv6 use Hexa-Decimal format separated by colon (:) .
• Components in Address format :
1.There are 8 groups and each group represents 2 Bytes (16-bits).
2.Each Hex-Digit is of 4 bits (1 nibble)
3.Delimiter used – colon (:)

Transition from IPv4 to IPv6 address
• Dual Stack Routers, Tunneling, and NAT Protocol Translation. These are
explained as following below.

• 2. Tunneling:
Tunneling is used as a medium to communicate the transit network
with the different IP versions.

• OSI Model and Protocol
stack

UNIT III
Transport and Application Layers

Transport layer protocols
Transport layer protocols are responsible for ensuring end-to-end
communication between devices
They also perform error detection

• Functions of Transport Layer
• The process to process delivery
• End-to-end connection between devices
• Multiplexing and Demultiplexing
• 1-X ,X-1
• Data integrity and error Correction
• Congestion Control
• Flow Control

Transport Layer Protocols
The transport layer is represented majorly by TCP and UDP protocols.
Today almost all operating systems support multiprocessing multi-user
environments. This transport layer protocol provides connections to the
individual ports.
1. UDP
UDP stands for User Datagram Protocol. User Datagram Protocol provides a
nonsequential transmission of data. It is a connectionless transport protocol.
UDP protocol is used in applications where the speed and size of data
transmitted is considered as more important than the security and reliability.
User Datagram is defined as a packet produced by User Datagram Protocol.
Services provided by User Datagram Protocol(UDP) are connectionless service,
faster delivery of messages, checksum, and process-to-process communication.

UDP
The User Datagram Protocol, or UDP, is a communication protocol used
for time-sensitive applications across the Internet for especially time-
sensitive transmissions such as video playback or DNS lookups

Advantages of UDP
•UDP also provides multicast and broadcast transmission of data.
•UDP protocol is preferred more for small transactions such as DNS lookup.
•It is a connectionless protocol, therefore there is no compulsion to have a
connection-oriented network.

TCP
TCP stands for Transmission Control Protocol. TCP protocol provides transport layer
services to applications. TCP protocol is a connection-oriented protocol. A secured
connection is being established between the sender and the receiver

Advantages of TCP
•TCP supports multiple routing protocols.
•TCP protocol operates independently of that of the operating
system.
•TCP protocol provides the features of error control and flow
control.
•TCP provides a connection-oriented protocol and provides the
delivery of data.

Application Layer
The application layer is the topmost layer of the OSI model and
the TCP/IP model. In TCP/IP model, the application layer is formed by combining
the top three layers, i.e., the application layer, the presentation layer, and the
session layer.
One of the most often used application protocols is HTTP (HyperText
Transfer Protocol), the foundation for the World Wide Web. Domain Name
System (DNS),

Domain Name System (DNS)
• A domain name serves as a distinctive identification for a website. To make it
simpler for consumers to visit websites, it is used in place of an IP address.
• A device connected to the internet is given an IP address, which is a numerical
identity. It’s used to pinpoint where on the internet a website or gadget is.
• An application called a DNS resolver is in charge of translating domain names
into IP addresses. The DNS resolver contacts a DNS server to seek the IP
address associated with a domain name when a user types it into their web
browser.

World Wide Web (WWW, W3)
Commonly referred to as WWW, W3, or the Web—is a system of interconnected
public webpages accessible through the Internet.
The World Wide Web -- also known as the web, WWW or W3 -- refers to all the
public websites or pages that users can access on their local computers and other
devices through the internet. These pages and documents are interconnected by means
of hyperlinks that users click on for information. This information can be in different

Hypertext Transfer Protocol (HTTP)
The Hypertext Transfer Protocol (HTTP) is the foundation of the World Wide
Web, and is used to load webpages using hypertext links. HTTP is an
application layer protocol designed to transfer information between networked
devices and runs on top of other layers of the network protocol stack.

Electronic mail
Electronic mail, commonly shortened to “email,” is a communication method
that uses electronic devices to deliver messages across computer networks.
"Email" refers to both the delivery system and individual messages that are sent
and received.
Features of email
•automatic reply to messages.
•auto-forward and redirection of messages.
•facility to send copies of a message to many people.
•automatic filing and retrieval of messages.
•addresses can be stored in an address book and retrieved instantly.
•notification if a message cannot be delivered.

QoS in Networking
Quality of service (QoS) is the use of mechanisms or technologies that work on a network to control
traffic and ensure the performance of critical applications with limited network capacity. It enables
organizations to adjust their overall network traffic by prioritizing specific high-performance applications.
QoS networking technology works by marking packets to identify service types
Types of network traffic
1.Bandwidth: The speed of a link. QoS can tell a router how to use bandwidth. For example, assigning a
certain amount of bandwidth to different queues for different traffic types.
2.Delay: The time it takes for a packet to go from its source to its end destination. This can often be
affected by queuing delay, which occurs during times of congestion and a packet waits in a queue before
being transmitted. QoS enables organizations to avoid this by creating a priority queue for certain types of
traffic.
3.Loss: The amount of data lost as a result of packet loss, which typically occurs due to network
congestion. QoS enables organizations to decide which packets to drop in this event.
4.Jitter: The irregular speed of packets on a network as a result of congestion, which can result in packets
arriving late and out of sequence. This can cause distortion or gaps in audio and video being delivered.

Cent-Server Programming
Client
A client is a program that runs on the local machine requesting service from the server. A client
program is a finite program means that the service started by the user and terminates when the
service is completed.
Server
A server is a program that runs on the remote machine providing services to the clients. When the
client requests for a service, then the server opens the door for the incoming requests, but it never
initiates the service.

Advantages of Client-server networks:
•Centralized: Centralized back-up is possible in client-server networks, i.e., all the data
is stored in a server.
•Security: These networks are more secure as all the shared resources are centrally
administered.
•Performance: The use of the dedicated server increases the speed of sharing resources.
This increases the performance of the overall system.
•Scalability: We can increase the number of clients and servers separately, i.e., the new
element can be added, or we can add a new node in a network at any time.

Congestion Control and Avoidance
Congestion Control is a mechanism that controls the entry of data packets into the network,
enabling a better use of a shared network infrastructure and avoiding congestive collapse.
Congestive-Avoidance Algorithms (CAA) are implemented at the TCP layer as the
mechanism to avoid congestive collapse in a network.
Congestion avoidance is a mechanism used to control service flows. A system configured
with congestion avoidance monitors network resource usage such as queues and memory
buffers. When congestion occurs or aggravates, the system starts to discard packets.
How to avoid congestion in a network
You can often reduce network congestion simply by increasing the available bandwidth so that the
network itself will be able to handle more data, and more devices at the same time.

OSI Security Architecture
The OSI (Open Systems Interconnection) Security Architecture defines a systematic
approach to providing security at each layer. It defines security services and security
mechanisms that can be used at each of the seven layers of the OSI model to provide
security for data transmitted over a network.
These security services and mechanisms help to ensure the confidentiality, integrity, and
availability of the data

OSI Security Architecture focuses on these concepts
• Security Attack:
• Security mechanism:
A security mechanism is a means of protecting a system, network, or device
against unauthorized access, tampering, or other security threats.
• Security Service:

Security Attacks
A security attack is an attempt by a person or entity to gain unauthorized access to disrupt or
compromise the security of a system, network, or device. These are defined as the actions that
put at risk an organization’s safety.
• Classified into 2 sub-categories:
• A. Passive Attack:
Attacks in which a third-party intruder tries to access the message/ content/ data being shared
by the sender and receiver by keeping a close watch on the transmission or eave-dropping the
transmission is called Passive Attacks. These types of attacks involve the attacker observing or
monitoring system, network, or device activity without actively disrupting or altering it
• B. Active Attacks:
Active attacks refer to types of attacks that involve the attacker actively disrupting or altering
system, network, or device activity. Active attacks are typically focused on causing damage or
disruption, rather than gathering information or intelligence. Here, both the sender and receiver
have no clue that their message/ data is modified by some third-party intruder. The message/
data transmitted doesn’t remain in its usual form and shows deviation from its usual behavior.

Security Mechanism
• The mechanism that is built to identify any breach of security or attack on the
organization, is called a security mechanism. Security Mechanisms are also
responsible for protecting a system, network, or device against unauthorized access,
tampering, or other security threats.
• Security mechanisms can be implemented at various levels within a system or network
and can be used to provide different types of security, such as confidentiality, integrity,
or availability.

Examples of security mechanisms
Encipherment (Encryption)
Involves the use of algorithms to transform data into a form that can only be read by
someone with the appropriate decryption key. Encryption can be used to protect data
it is transmitted over a network, or to protect data when it is stored on a device.
Digital signature
Security mechanism that involves the use of cryptographic techniques to create a
unique, verifiable identifier for a digital document or message, which can be used to
ensure the authenticity and integrity of the document or message.
Traffic padding
Is a technique used to add extra data to a network traffic stream in an attempt to
obscure the true content of the traffic and make it more difficult to analyze.
Routing control allows the selection of specific physically secure routes for
specific data transmission and enables routing changes, particularly when a gap in
security is suspected.

Security Services
Security services refer to the different services available for maintaining the security and
safety of an organization. They help in preventing any potential risks to security
• Security services are divided into 5 types:
• Authentication is the process of verifying the identity of a user or device in order to grant
or deny access to a system or device.
• Access control involves the use of policies and procedures to determine who is allowed to
access specific resources within a system.
• Data Confidentiality is responsible for the protection of information from being accessed
or disclosed to unauthorized parties.
• Data integrity is a security mechanism that involves the use of techniques to ensure that
data has not been tampered with or altered in any way during transmission or storage.
• Non- repudiation involves the use of techniques to create a verifiable record of the origin
and transmission of a message, which can be used to prevent the sender from denying that
they sent the message.

Benefits of OSI Architecture:
1. Providing Security:
2. Organising Task:
3. Meets International Standards:

Encryption
• Encryption is the process by which a readable message is converted to an unreadable
form to prevent unauthorized parties from reading it. Decryption is the process of
converting an encrypted message back to its original (readable) format.

Advanced Encryption Standard (AES)
• Advanced Encryption Standard (AES) is a specification for the encryption of
electronic data established by the U.S National Institute of Standards and
Technology (NIST)
• it takes 128 bits as input and outputs 128 bits of encrypted cipher text as output.
• it is performed using a series of linked operations which involves replacing and
shuffling of the input data.

• Encryption :
•
AES considers each block as a 16 byte (4 byte x 4 byte = 128 ) grid in a column major
arrangement.
• [ b0 | b4 | b8 | b12 |
• | b1 | b5 | b9 | b13 |
• | b2 | b6 | b10| b14 |
• | b3 | b7 | b11| b15 ]
• Each round comprises of 4 steps :
• SubBytes
• ShiftRows
• MixColumns
• Add Round Key

What Is Public Key Cryptography
• Public key encryption is also called asymmetric key encryption. As the name itself says,
an asymmetric key, two different keys are used for public-key encryption. One key is used
for the encryption process, and another key is used for the decryption process. Once the
key is decided for encryption and decryption, no other key will be used. One key is called
a public key from these two keys, and another one is called a private key.

RSAAlgorithm in Cryptography
RSA algorithm is an asymmetric cryptography algorithm. Asymmetric actually means that it works
on two different keys i.e. Public Key and Private Key. As the name describes that the Public Key is
given to everyone and the Private key is kept private.
An example of asymmetric cryptography:
1.A client (for example browser) sends its public key to the server and requests some data.
2.The server encrypts the data using the client’s public key and sends the encrypted data.
3.The client receives this data and decrypts it.
4.Rivest, Shamir, and Adelman (RSA).

Secure Hash Algorithm
• Secure Hash Algorithm is a cryptographic algorithm which takes an input and produces a 160-bit (20-byte) hash value.
• Input : hello world
• Output : 2aae6c35c94fcfb415dbe95f408b9ce91ee846ed
• Password storage. You must keep records of all of the username/password combinations people use to access your
resources. But if a hacker gains entry, stealing unprotected data is easy. Hashing ensures that the data is stored in a
scrambled state, so it's harder to steal.
• Digital signatures. A tiny bit of data proves that a note wasn't modified from the time it leaves a user's outbox and
reaches your inbox.
• Document management. Hashing algorithms can be used to authenticate data. The writer uses a hash to secure the
document when it's complete. The hash works a bit like a seal of approval.A recipient can generate a hash and compare
it to the original. If the two are equal, the data is considered genuine. If they don't match, the document has been
changed.
• File management. Some companies also use hashes to index data, identify files, and delete duplicates. If a system has
thousands of files, using hashes can save a significant amount of time.

DSA stands for Digital Signature Algorithm. It is a cryptographic algorithm used to generate digital
signatures,
A Digital Signature is a verification method made by the recipient to ensure the message was sent
from the authenticated identity. When a customer signs a check, the bank must verify that he issued
that specific check. In this case, a signature on a document acts as a sign of authentication and
verifies that the document is authentic.
DSA works by having two keys: a private key owned by the sender and a public key held by the
receiver.
The sender uses their private key to generate a signature for the message, which is then sent along
with it.
Then, the message receiver uses the sender's public key to verify that the signature is valid and that
the message has not been tampered with.
The verification process is done using unique algorithms that allow the receiver to validate the
signature without having access to the sender's private key.

Methods of Digital Signature
• These two are standard Approaches to implement the Digital Signature:
• Rivest-Shamir-Adleman (RSA)
• Digital Signature Algorithm (DSA)
Advantages of DSA
• Integrity -If something is altered in the content after the signature is made, then it
becomes invalid
• Efficiency: Digital signatures make the process of signing electronic and automate
it, giving way to fast online transactions
• Security: As long as the whole digital signing process is well organized, digital
signatures may prove to be secure.
• World Acceptance
• Cost Savings: The digital signing process discontinues the need for transporting
documents

Unit V
Hardware security practices.
• Introduction to hardware security.
• Hardware security is defined as the protection of physical devices from threats that
would facilitate unauthorized access to enterprise systems
• Hardware security is a device that scans employee endpoints or monitors network
traffic, such as a hardware firewall or a proxy server. Device-based hardware security
is also achieved through hardware security modules (HSM)

Key Threats to Enterprise Hardware
• Basic input-output systems (BIOS),
• motherboards,
• network cards,
• Wi-Fi cards,
• hard drives,
• graphics cards,
• systems-on-a-chip, and servers

Hardware Trojan
• In terms of Hardware security, It is a malicious modification of the circuitry
of an IC chip. It is done during the design or fabrication of chip (i.e. The chip
is modified without the possible knowledge of the person who designed it. )
• It is sometimes also known as ‘HT’. A Hardware Trojan or HT is something, a
piece of hardware, which is hiding inside another larger piece of hardware. It
wakes up at unpredictable times and does something malicious which is again
unpredictable with respect to user.

Properties of a Hardware Trojan
1.It can take place pre or post manufacturing.
2.It is inserted by some intellectual adversary.
3.It is extremely small hardware overhead.
4.It causes IC to malfunction in-field.
• The entire activity that the Trojan performs or executes is known as payload.

Components of a Hardware Trojan

NETWORK AND SECURITY-Dr.Poovendran R.pptx

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