Application Layer Protocols in Computer Network

FTP (File Transfer Protocol)

FTP is File Transfer Protocol.
It used to exchange files on the internet.
To enable the data transfer FTP uses TCP/IP, FTP is most commonly used to upload and download files from the internet.
FTP can be invoked from the command prompt or some graphical user interface.
FTP also allows to update (delete, rename, move, and copy) files at a server.
It uses a reserved port no 21.

Dynamic Host Configuration Protocol (DHCP) is used assigning IP addresses to computers in a network.
The IP addresses are assigned dynamically.
Certainly, using DHCP, the computer will have a different IP address every time it is connected to the network.
In some cases the IP address may change even when the computer is in network.
This means that DHCP leases out the IP address to the computer for sometime.
Clear advantage of DHCP is that the software can be used to manage IP address rather than the administrator.

The Hypertext Transfer Protocol (HTTP) is used to access the data on WWW(World Wide Web).
The functions of HTTP are the combination of FTP (File Transfer Protocol) and SMTP (Simple Mail Transfer Protocol).
HTTP is similar to FTP, because it uses only one TCP connection (data is transferred between Client and Sever).
In SMTP, the messages are stored and then forwarded to the destination, but the HTTP messages are delivered immediately.
HTTP uses the services of TCP on well-known port 80.

It is an application layer protocol, which can be used on the internet or LAN(Local Area Network).
It provides a bi-directional interactive text oriented communication service by using virtual terminal connection.
Telnet is basically a client server protocol, which is based on a reliable connection- oriented transport.
It uses a port number 23, to establish the connection with TCP (Transmission Control Protocol).