This document provides an overview of various application layer protocols including HTTP, HTTPS, SMTP, POP3, FTP, SFTP, SCP, Telnet, and SSH. It describes each protocol, including what they are used for and how they differ. Some key points: - HTTP and HTTPS are used to access data on the world wide web, with HTTPS providing encryption for secure transactions. - SMTP and POP3 are used for email, with SMTP sending messages between servers and POP3 allowing users to receive messages from their inbox. - FTP and SFTP are used for file transfer, with SFTP encrypting data for security unlike regular FTP. SCP also provides secure file transfer. - Tel

1. COMPUTER APPLICATIONS
CLASS X (Code 165)
TOPIC:
UNIT 1: Application Layer Protocols
By
HIMANSHU PATHAK

2. Contents
• Introduction
• Communication Protocol
• Mail Protocol
• File Transfer Protocol
• Remote Login Protocol

3. Introduction
• Application Layer uses protocols such as
HTTP(S) on client side applications like
browser.
• The application layer is responsible for
providing services to the user:
– Accessing the www
– Mail Services
– File Transfer and Access
– Remote Log-in

4. Communication Protocol: HTTP
• HTTP stands for Hyper-Text Transfer Protocol.
• HTTP is used mainly to access data on the world
wide web.
• HTTP provides standard rules for web browsers &
servers to communicate.
• An HTTP is a stateless protocol as each transaction
is executed separately without having any
knowledge of the previous transactions, which
means that once the transaction is completed
between the web browser and the server, the
connection gets lost.

5. Communication Protocol: HTTPS
• HTTPS stands for Hyper Text Transfer Protocol
Secure.
• It means all communications between your
browser and the website are encrypted.
• The use of HTTPS protocol is mainly required
where we need to enter the bank account
details.
• The HTTPS protocol is mainly used where we
require to enter the login credentials.

6. HTTP Vs. HTTPS
HTTP HTTPS
It is mainly used for those websites that
provide information like blog writing.
It is a secure protocol, so it is used for those
websites that require to transmit the bank
account details or credit card numbers.
The HTTP transmits the data over port
number 80.
The HTTPS transmits the data over port
number 443.
The page loading speed is fast.
The page loading speed is slow as compared
to HTTP because of the additional feature
that it supports, i.e., security.
It is an application layer protocol. It is a transport layer protocol.
It does not use SSL.
It uses SSL that provides the encryption of
the data.

7. Mail Protocol: SMTP
• SMTP stands for Simple Mail Transfer Protocol.
• SMTP is the standard mechanism for electronic
mail in the internet.
• The addressing system used by SMTP consists of
two parts: Local part & Domain part
• Local-part @ Domain-part
• The main purpose of SMTP is used to set up
communication rules between servers.
• Most email clients allow for transfers of up to 25
MB.

8. Mail Protocol: POP3
• The POP protocol stands for Post Office Protocol.
• POP3 is a client/server protocol in which e-mail is
received and held for you by your Internet server.
• Periodically, you (or your client e-mail receiver)
check your mail-box on the server and download
any mail, probably using POP3.
• This standard protocol is built into most popular
e-mail products, such as Eudora and Outlook
Express.

9. SMTP Vs. POP3
SMTP POP3
SMTP is used to send the email POP is used to receive email
SMTP acts as a MTA (Message Transfer
Agent)
POP3 is a MAA (Message Access Agent)
The port number of SMTP is 25. The port number of POP3 is 110.

10. File Transfer Protocol: FTP
• FTP stands for File Transfer Protocol.
• FTP is an application layer protocol which moves
files between local and remote file systems.
• FTP establishes two connections between the client
and the server:
– One connection is used for data transfer (port 20).
– And the other for control information (port 21).
• The control connection is maintained during the
entire FTP session while the data connection is
opened and then closed for each file transferred.

11. File Transfer Protocol: SFTP
• It stands for Secure File Transfer Protocol.
• It builds on the File Transfer Protocol (FTP) and
includes Secure Shell (SSH) security components.
• Secure Shell is a cryptographic component of
internet security.
• SSH and SFTP were designed by the Internet
Engineering Task Force (IETF) for greater web
security.
• SFTP transfers files security using SSH and encrypted
FTP commands to avoid password sniffing and
exposing sensitive information in plain text.

12. FTP Vs. SFTP
FTP SFTP
FTP uses 2 channels to transfer data SFTP usage 1 channel to transfer data
It usually runs on port no-21 It runs on port no-22
It does not encrypt the data before sending It encrypted data before sending

13. SCP
• SCP stands for Secure Copy Protocol.
• Secure copy (SCP) is a file transfer protocol,
which helps in transferring computer files
securely from a local host to a remote host.
• It works on the Secure Shell (SSH) protocol
technique.
• It doesn’t allow user to see and modify files on
the server.

14. SFTP Vs. SCP
SFTP SCP
SFTP is slow SCP is fast
SFTP has to ACK (acknowledge) every tiny
packet
SCP does not need to ACK (acknowledge)
SCP is built purely for file transfers. Generally
speaking, you can't generate directory
listings (to view files within a directory),
create directories, delete directories, delete
files, and so on.
SFTP, on the other hand, can readily perform
these operations on its own.

15. Remote Login Protocol: Telnet
• Telnet stands for Terminal Network.
• It is a type of protocol that enables one
computer to connect to local computer.
• Computer which starts connection known as
the local computer. Computer which is being
connected to i.e. which accepts the connection
known as remote computer.
• During telnet operation whatever that is
performing on the remote computer will be
displayed by local computer.

16. Remote Login Protocol: SSH
• The SSH protocol (also referred to as Secure
Shell) is a method for secure remote login from
one computer to another.
• It provides several alternative options for strong
authentication, and it protects the
communications security and integrity with
strong encryption.
• It is a secure alternative to the non-protected
login protocols (such as telnet) and insecure file
transfer methods (such as FTP).

17. Telnet Vs. SSH
TELNET SSH
Telnet uses port 23 SSH runs on port 22 by default
No privileges are provided for the user's
authentication.
SSH is a more secure protocol, so it uses
public-key encryption for authentication.
Suitable for private networks Suitable for public networks

18. Today we learn
• Communication protocols
• Remote login and file transfer protocols.
• In the next class, we will see Web Services in
detail.
•Thanks