Priyanka Shinde (M - 3248)
What is a protocol after all?
Protocol is a standard used to define a method of
exchanging data over a computer network such as local
area network, Internet, Intranet
Protocols define how messages are sent and received, i.e.
the format and order of them, what happens when
messages are transmitted and received.
Each protocol has its own method of how data is
formatted when sent and what to do with it once received,
how that data is compressed or how to check for errors in
The protocol can be implemented either in hardware or in
Internet Protocol (IP)
It is a protocol by which data is sent from one
computer to another on the Internet.
Each computer (known as a host) on the Internet
has at least one IP address that uniquely
identifies it from all other computers on the
When you send or receive data (for example, an
e-mail note or a Web page), the message gets
divided into little chunks called packets.
Packets can arrive in a different order than the order they were
sent in. The Internet Protocol just delivers them. It's up to
another protocol, the Transmission Control Protocol (TCP) to
put them back in the right order.
Each of these packets contains both the sender's Internet
address and the receiver's address
Protocol version 4 (IPv4) standard that features IP addresses
four bytes (32 bits) in length.
The newer Internet Protocol version 6 (IPv6) standard features
addresses 16 bytes (128 bits) in length.
Hypertext Transfer Protocol
HTTP is a set of standards that allow
users of the World Wide Web to
exchange information found on web
The term HTTP was coined by Ted
HTTP commonly utilizes port 80, 8008,
When wanting to access any web page
enter http:// in front of the web
address, which tells the browser to
communicate over HTTP
Hypertext Transfer Protocol over
It is a secure method of accessing or sending information across
a web page.
All data sent over HTTPS is encrypted before it is sent, this
prevents anyone from understanding that information if
Because data is encrypted over HTTPS, it is slower than HTTP,
which is why HTTPS is only used when requiring login
information or with pages that contain sensitive information
such as an online bank web page.
HTTPS uses port 443 to transfer its information.
HTTPS is first used in HTTP/1.1
File Transfer Protocol (FTP)
• Standard Internet protocol for transmitting files between
computers on the Internet.
• First proposed on April 16, 1971 by Abhay Bhushan
• Used to transfer Web page files from their creator to the
computer that acts as their server for everyone on the
• It's also commonly used to download programs and other
files to your computer from other servers.
• Your Web browser can also make FTP requests to
download programs you select from a Web page.
• Using FTP, you can also update (delete, rename,
move, and copy) files at a server.
• You need to logon to an FTP server.
• FTP is most commonly used to download a file
from a server using the Internet or to upload a file
to a server (e.g., uploading a Web page file to a
Interactions between email servers and
clients are governed by email protocols.
The most common email protocols are
POP - Post Office Protocol
IMAP - Internet Mail Access Protocol
SMTP - Simple Mail Transport Protocol
Most recent version of a standard protocol for
Provides a simple, standardized way for users
to access mailboxes and download messages
to their computers.
When using the POP protocol all eMail
messages will be downloaded from the mail
server to your local computer
Most POP clients also provide an option to
leave copies of email on the server.
Advantage is that once messages are downloaded
you can cut the internet connection and read your
email at your leisure without incurring further
protocol is built into most popular e-mail
products, such as Eudora and Outlook
It's also built into the Netscape and Microsoft
Internet Explorer browsers.
The conventional port number for POP3 is
IMAP was developed at Stanford University in 1986
Standard protocol for accessing e-mail from your local
The latest version, IMAP4, is similar to POP3 but
supports some additional features.
For example, with IMAP4, you can search through
your e-mail messages for keywords while the
messages are still on mail server. You can then choose
which messages to download to your machine.
Port - 143
Difference between POP3 & IMAP
It is a method of accessing
e-mail messages on a
server without having to
download them to your
local hard drive
POP3 requires users to
download messages to
their hard drive before
The advantage of using an IMAP mail server is that
users can check their mail from multiple computers
and always see the same messages.
This is because the messages stay on the server until
the user chooses to download them to his or her local
SMTP was created in the early 1980's
used by the Mail Transfer Agent (MTA) to deliver your eMail to the
recipient's mail server.
only be used to send emails, not to receive them.
This is why you need to specify both the POP or IMAP server and
the SMTP server when you configure your e-mail application.
SMTP usually is implemented to operate over Internet port 25.
An alternative to SMTP that is widely used in Europe is X.400.
Many mail servers now support Extended Simple Mail Transfer
Protocol (ESMTP), which allows multimedia files to be delivered as
Multipurpose Internet Mail
MIME was defined in 1992 by the Internet Engineering Task
Many e-mail clients now support MIME, which enables them to
send and receive graphics, audio, and video files via the
Internet mail system.
There are many predefined MIME types, such as GIF graphics
files and PostScript files.
In addition, MIME supports messages in character sets other
A new version, called S/MIME, supports encrypted messages.