Question

Different types of protocols and their functions

Answer 1

TCP

Transmission Control Protocol (TCP) A connection-oriented transport protocol. Connection-oriented transport protocols provide reliable transport, in that if a segment is dropped, the sender can detect that drop and retransmit that dropped
segment. Specifically, a receiver acknowledges segments that it receives. Based on those acknowledgments, a sender can determine which segments were successfully
received.

TCP operates at the transport layer of the OSI model.

TCP three-way handshake.

1. It sends a message called a SYN to the target host.

2. The target host opens a connection for the request and sends back an acknowledgment message called an ACK (or SYN ACK).

3. The host that originated the request sends back another acknowledgment, saying that it has received the ACK message and that the session is ready to be used to transfer data.

UDP

User Datagram Protocol A connectionless transport protocol. Connectionless transport protocols provide unreliable transport, in that if a segment is dropped, the sender is unaware of the drop, and no retransmission occurs.

UDP operates at the transport layer

SFTP

Secure File Transfer Protocol

A protocol that transfers files between clients securly,Based on Secure Shell (SSH) technology, provides robust authentication between sender and receiver. It also provides encryption capabilities, which means that even if packets are copied from the network, their contents remain hidden
from prying eyes.

TFTP

Trivial File Transfer Protocol 

A variation on FTP is TFTP, which is also a file transfer mechanism. However, TFTP does not have the security capability or the level of functionality that FTP has. TFTP, is most often associated with simple downloads, such as those associated with transferring firmware to a device such as a router and booting diskless workstations.

Another feature that TFTP does not offer is directory navigation.

TFTP is an application layer protocol that uses UDP, which is a 

SMTP

Simple Mail Transfer Protocol 

SMTP is a protocol that defines how mail messages
are sent between hosts. SMTP uses TCP connections to guarantee error-free delivery of messages. SMTP is not overly sophisticated and requires that the destination host always be available.

SMTP can be used to both send and receive mail. Post Office Protocol version 3 (POP3) and Internet Message Access Protocol version 4 (IMAP4) can be used only to receive mail.

HTTP

Hypertext Transfer Protocol

HTTP, is the protocol that enables text, graphics, multimedia, and other material to be downloaded from an HTTP server. HTTP defines what actions can be requested by clients and how servers should answer those requests.

HTTP is a connection-oriented protocol that uses TCP as a transport protocol.

HTTPS

Hypertext Transfer Protocol Secure 

One of the downsides of using HTTP is that HTTP requests are sent in clear text. For some applications, such as e-commerce, this method to exchange information is unsuitable—a more secure method is needed. The solution is
HTTPS, which uses a system known as Secure Socket Layer (SSL), which encrypts the information sent between the client and host.

POP3

Post Office Protocol Version 3

A mechanisms for downloading, or pulling, email from a server. They are necessary because although the mail is transported around the network via SMTP, users cannot always immediately read it, so it must be stored in a central location. From this location, it needs to be downloaded
or retrieved, which is what POP3 enable you to do.