FTP

o FTP stands for File transfer protocol.

o FTP is a standard internet protocol provided by TCP/IP used for transmitting the
files from one host to another.
o It is mainly used for transferring the web page files from their creator to the
computer that acts as a server for other computers on the internet.
o It is also used for downloading the files to computer from other servers.

Objectives of FTP
o It provides the sharing of files.
o It is used to encourage the use of remote computers.
o It transfers the data more reliably and efficiently.

Why FTP?
Although transferring files from one system to another is very simple and straightforward,
but sometimes it can cause problems. For example, two systems may have different file
conventions. Two systems may have different ways to represent text and data. Two
systems may have different directory structures. FTP protocol overcomes these problems
by establishing two connections between hosts. One connection is used for data transfer,
and another connection is used for the control connection.

Mechanism of FTP
The above figure shows the basic model of the FTP. The FTP client has three components:
the user interface, control process, and data transfer process. The server has two
components: the server control process and the server data transfer process.

There are two types of connections in FTP:

o Control Connection: The control connection uses very simple rules for
communication. Through control connection, we can transfer a line of command
or line of response at a time. The control connection is made between the control
processes. The control connection remains connected during the entire
interactive FTP session.
o Data Connection: The Data Connection uses very complex rules as data types
may vary. The data connection is made between data transfer processes. The
data connection opens when a command comes for transferring the files and
closes when the file is transferred.

FTP Clients
o FTP client is a program that implements a file transfer protocol which allows you
to transfer files between two hosts on the internet.
o It allows a user to connect to a remote host and upload or download the files.
o It has a set of commands that we can use to connect to a host, transfer the files
between you and your host and close the connection.
o The FTP program is also available as a built-in component in a Web browser.
This GUI based FTP client makes the file transfer very easy and also does not
require to remember the FTP commands.

Advantages of FTP:
 o Speed: One of the biggest advantages of FTP is speed. The FTP is one of the
fastest way to transfer the files from one computer to another computer.
o Efficient: It is more efficient as we do not need to complete all the operations to
get the entire file.
o Security: To access the FTP server, we need to login with the username and
password. Therefore, we can say that FTP is more secure.
o Back & forth movement: FTP allows us to transfer the files back and forth.
Suppose you are a manager of the company, you send some information to all
the employees, and they all send information back on the same server.

Disadvantages of FTP:
o The standard requirement of the industry is that all the FTP transmissions should
be encrypted. However, not all the FTP providers are equal and not all the
providers offer encryption. So, we will have to look out for the FTP providers that
provides encryption.
o FTP serves two operations, i.e., to send and receive large files on a network.
However, the size limit of the file is 2GB that can be sent. It also doesn't allow
you to run simultaneous transfers to multiple receivers.
o Passwords and file contents are sent in clear text that allows unwanted
eavesdropping. So, it is quite possible that attackers can carry out the brute force
attack by trying to guess the FTP password.
o It is not compatible with every system.

Electronic Mail (e-mail) is one of the most widely used services of

the Internet. This service allows an Internet user to send a message in
a formatted manner (mail) to other Internet users in any part of the world.
Message in the mail not only contain text, but it also contains images, audio
and videos data. The person who is sending mail is called sender and
person who receives mail is called the recipient. It is just like postal mail
service.
Format of E-mail :
An e-mail consists of three parts that are as follows :
1. Envelope
2. Header
3. Body
These are explained as following below.
1. Envelope :
The envelope part encapsulates the message. It contains all information that
is required for sending any e-mail such as destination address, priority and
security level. The envelope is used by MTAs for routing message.

2. Header :
The header consists of a series of lines. Each header field consists of a
single line of ASCII text specifying field name, colon and value. The main
header fields related to message transport are :
1. To: It specifies the DNS address of the primary recipient(s).
2. Cc : It refers to carbon copy. It specifies address of secondary
recipient(s).
3. BCC: It refers to blind carbon copy. It is very similar to Cc. The only
difference between Cc and Bcc is that it allow user to send copy to the
third party without primary and secondary recipient knowing about this.
4. From : It specifies name of person who wrote message.
5. Sender : It specifies e-mail address of person who has sent message.
6. Received : It refers to identity of sender’s, data and also time message
was received. It also contains the information which is used to find bugs in
routing system.
7. Return-Path: It is added by the message transfer agent. This part is used
to specify how to get back to the sender.
3. Body:- The body of a message contains text that is the actual
content/message that needs to be sent, such as “Employees who are eligible
for the new health care program should contact their supervisors by next
Friday if they want to switch.” The message body also may include
signatures or automatically generated text that is inserted by the sender’s
email system.
The above-discussed field is represented in tabular form as follows :
 Header Meaning

To: E-mail address of primary receipt(s).

Cc: E-mail address of secondary receipt(s).

Bcc: E-mail address for blind carbon copies.

From: Person or people who have created a message.

Sender: E-mail address of the actual sender.

Received: It is used to specify how to get back to the sender.

It can be used to identify a path back to the

Return-Path
sender.
In addition to above-discussed fields, the header may also contain a variety
of other fields which are as follows :

Header Meaning

Date: Date and time when the message was sent.

Reply-To: It contains e-mail address to which replies should be sent.

It refers to the unique number for referencing this message

Message-Id:
later.

In-Reply-To: Message-Id of a message to which this is as a reply.

References: It contains other relevant message-ids.

Keywords: User-chosen keywords.

Subject: It contains short summary of message for one-line display.