UNIT-VI

Overview of Application Layer

6.1 Domain Name Space (DNS), DDNS,
6.2 TELNET, EMAIL, File Transfer
Protocol (FTP), WWW, HTTP, SNMP,
Bluetooth, Dr. R C Sahoo
6.3 Firewalls Assoc. Professor
6.4 Basic concepts of Cryptography (CSE)

Dr. Ramesh Ch Sahoo

Secure Communication
Needs and Requirements

● Requirements of secure communication

1. Secrecy
– Only intended receiver understands the message
2. Authentication
– Sender and receiver need to confirm each others
identity
3. Message Integrity
– Ensure that their communication has not been
altered, either maliciously or by accident during
transmission

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 Basic concepts of Cryptography
Approaches to Secure Communication
● Steganography
○ “covered writing”
○ hides the existence of a message
○ depends on secrecy of method
● Cryptography
○ “hidden writing”
○ hide the meaning of a message
○ depends on secrecy of a short key, not
method

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Cryptography is the science of secret, or hidden writing
Cryptography derived its name from a Greek word called “krypto’s” which
means “Hidden Secrets”.
Cryptography is the practice and study of keeping message secure. It is the Art or
Science of converting a plain intelligible data into an unintelligible data and
again retransforming that message into its original form.
It provides :
Confidentiality,
Integrity, and
Accuracy.

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 PURPOSE OF CRYPTOGRAPHY

● Authentication: The process of proving one's identity. (The primary forms of host-to-
host authentication on the Internet today are name-based or address-based, both of
which are notoriously weak.)
● Privacy/confidentiality: Ensuring that no one can read the message except the intended
receiver.
● Integrity: Assuring the receiver that the received message has not been altered in any
way from the original.
● Non-repudiation: A mechanism to prove that the sender really sent this message.

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Terms: Cryptography, cryptanalysis,
● Cryptography: Theand cryptology
process of designing systems that achieve secure
communications
○ Traditionally, designing algorithms/protocols
○ Nowadays, often synonym with cryptology

● Cryptanalysis: Breaking such systems. (The techniques used to recover the

secret information hidden in cryptographic systems)
○ Breaking algorithms/protocols

● Cryptology: The study of communication over non-secure channels, and

related problems .
both cryptography & cryptanalysis
○ Becoming less common
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 Encryption
Cipher
● Cipher is a method for encrypting messages

Plain Text Encryption Cipher Text Decryption Plain Text

Algorithm Algorithm

Key A Key B

● Encryption algorithms are standardized & published

● The key which is an input to the algorithm is secret
○ Key is a string of numbers or characters
○ If same key is used for encryption & decryption the
algorithm is called symmetric
○ If different keys are used for encryption & decryption the
algorithm is called asymmetric

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Types of Cryptography

 Symmetric Key Cryptography

 Asymmetric Key Cryptography
 Hash Functions

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Symmetric Key Cryptography

 Also known as Secret Key Cryptography or Conventional Cryptography.

 Symmetric Key Cryptography is an encryption system in which the sender and
receiver of a message share a single, common key that is used to encrypt and
decrypt the message.
 The Algorithm use is also known as a secret key algorithm or sometimes called a
symmetric algorithm.
 The key for encrypting and decrypting the file had to be known to all the recipients.
Else, the message could not be decrypted by conventional means.

mathematically have:
Y = EK(X)

X = DK(Y)

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 Techniques Used in Symmetric Key Cryptography

Substitution Techniques
Caesar Cipher
Monoalphabetic Ciphers
Playfair Cipher
Hill Cipher
Polyalphabetic Ciphers
One-Time Pad (OTP)

Transposition Techniques
Rail Fence Cipher
Columnar Transposition

Types of Symmetric Key

Cryptography
1.Stream Ciphers

2.Block Ciphers
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Caesar Cipher
To cipher a given text, we need an integer value, known as a shift. The shift indicates the
number of spots each letter of the text has been moved down. The encryption can be
represented using modular arithmetic by first transforming the letters into numbers, according
of a letter by a shift 𝑛 is shown here:
to the scheme:
Encryption
• A = 0, B = 1, C = 2,…Z = 25
En​(x) = (x + n) mod 26 (Encryption Phase with
shift 𝑛)
Dn​(x) = (x−n) mod 26 (Decryption Phase with
shift 𝑛)

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 Playfair Cipher
● Playfair cipher is an encryption algorithm to encrypt or encode a
message. It is the same as a traditional cipher. The only difference is
that it encrypts a digraph (a pair of two letters) instead of a single
letter.

● It initially creates a key-table of 5*5 matrix. The matrix contains

alphabets that act as the key for encryption of the plaintext. Note that
any alphabet should not be repeated. Another point to note that there
are 26 alphabets and we have only 25 blocks to put a letter inside it.
Therefore, one letter is excess so, a letter will be omitted (usually J) from
the matrix. Nevertheless, the plaintext contains J, then J is replaced by I.
It means treat I and J as the same letter, accordingly.

● Since Playfair cipher encrypts the message digraph byDr. Ramesh

digraph.
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 Playfair Cipher
Fill the first row (left to right) with the letters of the given keyword (ATHENS). If the keyword has duplicate
letters (if any) avoid them. It means a letter will be considered only once. After that, fill the remaining letters in
alphabetical order. Let's create a 5*5 key-matrix for the keyword ATHENS.

A T H E N

S B C D F

G I/J K L M

O P Q R U

V W X Y Z

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 Playfair Cipher RULE
1. First, split the plaintext into digraphs (pair of two letters). If the plaintext has
the odd number of letters, append the letter Z at the end of the plaintext. It
makes the plaintext of even For example, the plaintext MANGO has five
letters. So, it is not possible to make a digraph. Since, we will append a
letter Z at the end of the plaintext, i.e. MANGOZ.
2. After that, break the plaintext into digraphs (pair of two letters). If any letter
appears twice (side by side), put X at the place of the second occurrence.
Suppose, the plaintext is COMMUNICATE then its digraph becomes CO MX
MU NI CA TE. Similarly, the digraph for the plaintext JAZZ will be JA ZX ZX,
and for plaintext GREET, the digraph will be GR EX ET.
3. if both letters fall in the same row, replace each with letter to right (wrapping
back to start from end),
4. if both letters fall in the same column, replace each with the letter below it
(again wrapping to top from bottom),
5. otherwise each letter is replaced by the one in its row in the column of the
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 Playfair Cipher
● Example of Playfair Cipher
● Suppose, the plaintext is COMMUNICATION and the key that we will
use to encipher the plaintext is COMPUTER. The key can be any
word or phrase. Let's encipher the message COMMUNICATION.
● 1. First, split the plaintext into digraph (by rule 2) i.e. CO MX MU NI
CA TE.
● 2. Construct a 5*5 key-matrix (by rule 3). In our case, the key
is COMPUTER.

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 Playfair Cipher
3. Now, we will traverse in key-matrix pair by pair and find the corresponding
encipher for the pair.
○ The first digraph is CO. The pair appears in the same row. By using Rule
4(i) CO gets encipher into OM.
○ The second digraph is MX. The pair appears in the same column. By
using Rule 4(ii) MX gets encipher into RM.
○ The third digraph is MU. The pair appears in the same row. By using Rule
4(i) MU gets encipher into PC.
○ The fourth digraph is NI. The pair appears in different rows and different
columns. By using Rule 4(iii) NI gets encipher into SG.
○ The fifth digraph is CA. The pair appears in different rows and different
columns. By using Rule 4(iii) CA gets encipher into PT.
○ The sixth digraph is TE. The pair appears in the same row. By using Rule
4(i) TE gets encipher into ER.
● Therefore, the plaintext COMMUNICATE gets encipher (encrypted)
into OMRMPCSGPTER.

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Asymmetric Key Cryptography

Asymmetric cryptography , also known as Public-key cryptography, refers to a

cryptographic algorithm which requires two separate keys, one of which is private and
one of which is public. The public key is used to encrypt the message and the private
one is used to decrypt the message.

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SECRECY/ CONFIDENTIALITY (A sends to B)
EncryptPUBLIC KEY (PUB) (message) = ciphertext
DecryptPRIVATE KEY (PRB) (ciphertext) = message

AUTHENTICATION (A send to B)
EncryptPRIVATE KEY (PRA) (message) = ciphertext
DecryptPUBLIC KEY (PUA) (ciphertext) = message

BOTH(A send to B)
EncryptPUBLIC KEY (PUB) (EncryptPRIVATE KEY (PRA) (message)) = ciphertext
DecryptPUBLIC KEY (PUA) (DecryptPRIVATE KEY (PRB) (ciphertext)) = message

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 DOMAIN NAME SYSTEM (DNS)

Since the Internet is so huge today, a central directory system cannot hold all the
mapping. In addition, if the central computer fails, the whole communication network
will collapse.

A better solution is to distribute the information among many computers in the world.
In this method, the host that needs mapping can contact the closest computer holding
the needed information. This method is used by the Domain Name System (DNS).

Figure shows how TCP/IP uses a DNS

client and a DNS server to map a name
to an address. A user wants to use a file
transfer client to access the
corresponding file transfer server
running on a remote host. The user
knows only the file transfer server
name, such as afilesource.com.
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 Working of DNS
 It is a network communication protocol of the client/server
type in which the client sends requests to the DNS server.
On the other hand, the server sends responses to these
clients.

 The client requests consist of a name that gets converted

into IP addresses called a forward DNS lookup. The
requests that contain an IP address get converted into a
name called the reverse DNS lookups.

 In order to keep the names of all hosts that are accessible

via the internet, DNS creates a distributed database.

 When a client, such as a web browser, submits a request

with a hostname, a piece of software, such as a DNS
resolver, submits a request to the DNS server to acquire
the IP address of the hostname. The request is forwarded
to another DNS server if the DNS server does not have the
IP address linked to a hostname. If the resolver receives an
IP address, it completes the request over the internet
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Types of Domain

1. Generic domains: .com(commercial), .edu(educational), .mil(military), .org(nonprofit

organization), .net(similar to commercial) all these are generic domains.
2. Country domain: .in (India) .us .uk
3. Inverse domain: if we want to know what is the domain name of the website. Ip to domain
name mapping. So DNS can provide both the mapping for example to find the IP addresses of
geeksforgeeks.org then we have to type
Who “owns” DNS?
The Internet needs governance
– IP addresses, AS numbers, DNS, and other Internet names/numbers
– Internet Assigned Numbers Authority (IANA) has the authority to manage the numbers

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Dr. Ramesh Ch Sahoo
Domain Name Space:

To have a hierarchical name space, a domain name space was designed.

In this design the names are defined in an inverted-tree structure with the
root at the top. The tree can have only 128 levels: level 0 (root) to level
127 (see Figure below).
Label:
Each node in the tree has a label, which is a string with a maximum of 63
characters. The root label is a null string (empty string). DNS requires that
children of a node (nodes that branch from the same node) have different
labels, which guarantees the uniqueness of the domain names.
Domain Name:
Each node in the tree has a domain name. A full domain name is a
sequence of labels separated by dots (.). The domain names are always
read from the node up to the root.
The last label is the label of the root (null). This means that a full domain
name always ends in a null label, which means the last character is a dot
because the null string is nothing. Figure 5.7 shows some domain names.
Domain:
A domain is a subtree of the domain name space. The name of the
domain is the name of the node at the top of the subtree. Figure 5.8 shows
some domains. Note that a domain may itself be divided into domains.

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 HyperText Transfer Protocol (HTTP):

The HyperText Transfer Protocol (HTTP) is used to define how the client-server programs can
be written to retrieve web pages from the Web. An HTTP client sends a request; an HTTP server
returns a response. The server uses the port number 80; the client uses a temporary port
number. HTTP uses the services of TCP, which, as discussed before, is a connection-oriented and
reliable protocol.
 It is a protocol used to access the data on the World Wide Web (www).
 The HTTP protocol can be used to transfer the data in the form of plain text, hypertext, audio,
video, and so on.
 This protocol is known as HyperText Transfer Protocol because of its efficiency that allows us
to use in a hypertext environment where there are rapid jumps from one document to
another document.
 HTTP is similar to the FTP as it also transfers the files from one host to another host. But,
HTTP is simpler than FTP as HTTP uses only one connection, i.e., no control connection to
transfer the files.
 HTTP is used to carry the data in the form of MIME-like format.
 HTTP is similar to SMTP as the data is transferred between client and server. The HTTP differs
from the SMTP in the way the messages are sent from the client to the server and from
server to the client. SMTP messages are stored and forwarded while HTTP messages are
delivered immediately.
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HTTP Request
HTTP request is simply termed as the information or data that is needed by Internet browsers for
loading a website. This is simply known as HTTP Request.
There is some common information that is generally present in all HTTP requests. These are
mentioned below.
• HTTP Version
• URL
• HTTP Method
• HTTP Request Headers
• HTTP Body
HTTP Request Headers
HTTP Request Headers generally store information in the form of key-value and must be present in
each HTTP Request. The use of this Request Header is to provide core information about the
client’s information, etc.
HTTP Request Body
HTTP Request Body simply contains the information that has to be transferred. HTTP Request has
the information or data to be sent to these browsers.
HTTP Method
HTTP Methods are simply HTTP Verb. In spite of being present so many HTTP Methods, the most
common HTTP Methods are HTTP GET and HTTP POST. These two are generally used in HTTP
cases. In HTTP GET, the information is received in the form of a website.
For more, refer to the Difference Between HTTP GET and HTTP POST. Dr. Ramesh Ch Sahoo
HTTP Response

HTTP Response is simply the answer to what a Server gets when the request is raised. There are
various things contained in HTTP Response, some of them are listed below.
• HTTP Status Code
• HTTP Headers
• HTTP Body
HTTP Status Code
HTTP Status Codes are the 3-Digit codes that tell the message or simply tell us about the HTTP
Request whether it has been completed or not. There are simply 5 types of status codes.
• Informational
• Successful
• Re-directional
• Client-Error
• Server-Error
HTTP Response Headers
HTTP Response headers are simply like an HTTP Request where it has that work to send some
important files and data to the HTTP Response Body.
HTTP Response Body
HTTP Responses are the responses that are received successfully upon the request. Generally, it
comes under the requests generated by the web. In most cases, the request is of transferring the
HTML data into a webpage.
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Web Caching: Proxy Servers:
HTTP supports proxy servers. A proxy server is a
computer that keeps copies of responses to recent
requests. The HTTP client sends a request to the proxy
server. The proxy server checks its cache.
If the response is not stored in the cache, the proxy
server sends the request to the corresponding server.
Incoming responses are sent to the proxy server and
stored for future requests from other clients.
The proxy server reduces the load on the original
server, decreases traffic, and improves latency.
However, to use the proxy server, the client must be
configured to access the proxy instead of the target
server.
HTTP Security:
HTTP per se does not provide security. HTTP can be run
over the Secure Socket Layer (SSL). In this case, HTTP is
referred to as HTTPS. HTTPS provides confidentiality,
client and server authentication, and data integrity.

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Dr. Ramesh Ch Sahoo
Features of HTTP:

• Connectionless protocol: HTTP is a connectionless protocol.

HTTP client initiates a request and waits for a response from the
server. When the server receives the request, the server
processes the request and sends back the response to the HTTP
client after which the client disconnects the connection. The
connection between client and server exist only during the
current request and response time only.
• Media independent: HTTP protocol is a media independent as
data can be sent as long as both the client and server know how
to handle the data content. It is required for both the client and
server to specify the content type in MIME-type header.
• Stateless: HTTP is a stateless protocol as both the client and
server know each other only during the current request. Due to
this nature of the protocol, both the client and server do not
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 World Wide Web (WWW)
The idea of the Web was first proposed by Tim Berners-Lee in 1989. The Web today is a repository
of information in which the documents, called web pages, are distributed all over the world and
related documents are linked together.

The World Wide Web’s operation is built on several technologies, including Hypertext Markup
Language (HTML), web browsers, and Hypertext Transfer Protocol (HTTP). To access webpages,
you’ll need a Web browser. Web browsers are programs that use the Internet to view information,
data, images, animation, and video. Web browsers provide a software interface for accessing
hyperlinked material on the World Wide Web.

Components of the Web

There are 3 components of the web:
• Uniform Resource Locator (URL): serves as a system for resources on the web.
• Hyper Text Transfer Protocol (HTTP): specifies communication of browser and server.
• Hyper Text Markup Language (HTML): defines the structure, organisation and content of a
web page.

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 WWW Documents

Web Documents:
The documents in the WWW can be grouped into three broad categories: static, dynamic, and
active.
Static documents are fixed-content documents that are created and stored in a server. The
client can get a copy of the document only. In other words, the contents of the file are determined
when the file is created, not when it is used.
Static documents are prepared using one of several languages: HyperText Markup Language
(HTML), Extensible Markup Language (XML), Extensible Style Language (XSL), and Extensible
Hypertext Markup Language (XHTML).
A dynamic document is created by a web server whenever a browser requests the document.
When a request arrives, the web server runs an application program or a script that creates the
dynamic document.
The server returns the result of the program or script as a response to the browser that requested
the document. Because a fresh document is created for each request, the contents of a dynamic
document may vary from one request to another. A very simple example of a dynamic document
is the retrieval of the time and date from a server.
Active Documents: For many applications, we need a program or a script to be run at the client
site. These are called active documents. For example, suppose we want to run a program that
creates animated graphics on the screen or a program that interacts with the user.

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 System Architecture

From the user’s point of view, the web consists of a vast, worldwide connection of documents or
web pages.
The pages can be retrieved and viewed by using browsers of which internet explorer, Netscape
Navigator, Google Chrome, etc are the popular ones.

The basic model of how the web works are shown in the figure below. Here the browser is
displaying a web page on the client machine. When the user clicks on a line of text that is linked to
a page on the abd.com server, the browser follows the hyperlink by sending a message to the
Working of WWW
abd.com server asking it for the page.
A Web browser is used to access web pages. Web
browsers can be defined as programs which display
text, data, pictures, animation and video on the
Internet. Hyperlinked resources on the World Wide Web
can be accessed using software interfaces provided by
Web browsers. Initially, Web browsers were used only
for surfing the Web but now they have become more
universal.

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 File Transfer Protocol (FTP)

File Transfer Protocol (FTP) is a network protocol used to transfer files between
machines on a TCP/IP network. FTP employs a client-server architecture; the client has
an FTP client installed and establishes a connection to an FTP server running on a
remote machine. After the connection has been established and the user is
successfully authenticated, the data transfer phase can begin. Note that, although FTP
does support user authentication, all data is sent in clear text, including usernames
and passwords.

A user wants to transfer files from Host A to the FTP server. The user will start an
FTP client program and initiate the connection:
Although many file transfers can be conducted using HTTP -- another protocol in the
TCP/IP suite -- FTP is still commonly used to transfer files behind the scenes for other
applications, such as banking services. It's also sometimes used to download new apps
via web browsers.
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How does FTP work?
FTP is a client-server protocol that relies on two communications channels between the client and server:
a command channel for controlling the conversation and a data channel for transmitting file content.
A typical FTP transfer works in the following way:
1. A user typically needs to log on to the FTP server, although some servers make some or all of their
content available without a login, a model known as anonymous FTP.

2. The client initiates a conversation with the server when the user requests to download a file.

3. Using FTP, a client can upload, download, delete, rename, move and copy files on a server.
FTP sessions work in active or passive modes in the following ways:
• Active mode. After a client initiates a session via a command channel request, the server creates a
data connection back to the client and begins transferring data.

• Passive mode. The server uses the command channel to send the client the information it needs to
open a data channel. Because the client is initiating all connections in passive mode, it works well
across firewalls and Network Address Translation gateways.

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Users can work with FTP via a
simple command-line interface
from a console or terminal
window in Microsoft Windows,
Apple macOS or Linux. They can
also use a dedicated graphical
user interface designed for FTP.
Web browsers can also serve as
FTP clients. Using FTP through
an FTP client is the most
common use case, as FTP
clients are easier to manage,
more flexible and more powerful.

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FTP types
An FTP server and client software can conduct a file transfer using FTP in the following ways:
• Anonymous FTP. This most basic form of FTP provides support for data transfers without encrypting data or using a
username and password. It's commonly used to download material that's allowed for unrestricted distribution. It works
on port 20 while in active mode and port 21 for control commands.

• Password-protected FTP. This is also a basic FTP service, but it requires the use of a username and password,
though the service might not be encrypted or secure. It also works on the same ports as anonymous FTP.

• FTP Secure (FTPS). Sometimes referred to as FTP Secure Sockets Layer (FTP-SSL), this approach enables implicit
Transport Layer Security (TLS) as soon as an FTP connection is established. FTPS was initially used to help enable
a more secure form of FTP data transfer. It typically defaults to port 990 for implicit FTPS and port 21 for explicit
FTPS.

• FTP over explicit SSL/TLS (FTPES). This approach enables explicit TLS support by upgrading an FTP connection
over port 21 to an encrypted connection. Web and file-sharing services commonly use this approach to enable secure
file transfers.

• Secure FTP (SFTP). This technically isn't an FTP protocol, but it functions similarly. Rather, SFTP is a subset of the
Secure Shell (SSH) protocol that runs over port 22. Systems administrators commonly use SSH to remotely and
securely access systems and applications, and SFTP provides a mechanism within SSH for secure file transfer.
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FTP's uses and benefits
FTP is a standard network protocol that enables expansive file transfer capabilities across IP networks. File and data
transfer can be managed with other mechanisms besides FTP -- such as email or an HTTP web service. But these other
options lack the clarity of focus, precision and control that FTP and its later iterations provide. Likewise, without FTP's
ability to transfer large file sizes simultaneously, users would have to transfer multiple large files one by one.
FTP is used for file transfers between systems and has multiple common use cases, including the following:
• Backup. Backup services or individual users can use FTP to back up data from one location to a secured backup
server running FTP services.

• Replication. Similar to backup, replication involves duplication of data from one system to another but takes a more
comprehensive approach to provide higher availability and resilience. FTP can also be used to facilitate this.

• Access and data loading. FTP is also commonly used to access shared web hosting and cloud services as a
mechanism to load data onto a remote system.

• Transferring large file sizes. FTP is commonly used to transfer large media files, such as code repositories, videos
and backups between production teams.
Although FTP can transfer large files, activities like streaming video content, pla

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FIREWALLS

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Dr. Ramesh Ch Sahoo
 SNMP — Simple Network Management Protocol
Simple Network Management Protocol
(SNMP) is a networking protocol used
for the management and monitoring
of network-connected devices in
Internet Protocol networks. The SNMP
protocol is embedded in multiple local
devices such as routers, switches,
servers, firewalls, and wireless access
points accessible using their IP
address. SNMP provides a common
mechanism for network devices to
relay management information within
single and multi-vendor LAN or WAN
environments. It is an application
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 SNMP has two components Manager and agent.
 The manager is a host that controls and monitors a set of agents such as
routers.
 It is an application layer protocol in which a few manager stations can
handle a set of agents.
 The protocol designed at the application level can monitor the devices
made by different manufacturers and installed on different physical
networks.
Agents and Managers:
 It 1.
is Agent:
used inThis
a heterogeneous network
is a software module made
that of different
resides LANs device.
in a managed and WANsAn
connected
agent byhasrouters
local or gateways. of management information and can
knowledge
translate that information to/from the SNMP protocol.
2. Manager: It's software that runs on a workstation or server and is
used to query agents and sometimes set values on the agents.
Managers collect information from agents, request actions from them,
and even send them configurations.
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Management Components
 Management is not achieved only through the SNMP protocol but also the
use of other protocols that can cooperate with the SNMP protocol.
Management is achieved through the use of the other two protocols: SMI
(Structure of management information) and MIB(management information
base).
 Management is a combination of SMI, MIB, and SNMP. All these three
SMI
protocols such as abstract syntax notation 1 (ASN.1) and basic encoding
The SMI(BER).
rules (Structure of management information) is a component used in network
management. Its main function is to define the type of data that can be stored in an
object and to show how to encode the data for the transmission over a network.
MIB
• The MIB (Management information base) is a second component for the network
management.
• Each agent has its own MIB, which is a collection of all the objects that the manager
can manage. MIB is categorized into eight groups: system, interface, address
translation, ip, icmp, tcp, udp, and egp. These groups are under the mib object.
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 SNMP defines five types of messages: GetRequest, GetNextRequest, SetRequest,
GetResponse, and Trap.
GetRequest: The GetRequest message is sent from a
manager (client) to the agent (server) to retrieve the value
of a variable.
GetNextRequest: The GetNextRequest message is sent
from the manager to agent to retrieve the value of a
variable. This type of message is used to retrieve the values
of the entries in a table. If the manager does not know the
indexes of the entries, then it will not be able to retrieve the
values. In such situations, GetNextRequest message is used
to define an object.
GetResponse: The GetResponse message is sent from an
agent to the manager in response to the GetRequest and
GetNextRequest message. This message contains the value
of a variable requested by the manager.
SetRequest: The SetRequest message is sent from a
manager to the agent to set a value in a variable.
Trap: The Trap message is sent from an agent to the Dr. Ramesh Ch Sahoo