In computers, a protocol is a set of well defined rules which govern the way devices communicate. In Internet world, the communication is mostly, but not always, managed through TCP (Transmission Control Protocol) or UDP (User Datagram Protocol). This article briefs only the basics of these internet protocols.
TCP: Transmission Control Protocol, or the TCP, is one of the major protocols involved in internet communication. Websites, email, file transfer etc. rely on TCP for data transfer. This protocol is designed for reliability of communication.
UDP: User Datagram Protocol, or the UDP, is designed for reduced time delay between communicating parties, at the cost of reliability and the order of messages being delivered. Torrents, online gaming applications, DNS etc. use this layer to provide better real time response.
HTTP: Hypertext Transfer Protocol, extensively used for websites, is a protocol for communication between a server and a client. While TCP, UDP etc. manage the transportation of data over the network, HTTP works closely with applications to provide them a communication element. HTTP uses another protocol to transmit data (mostly TCP).
FTP: It is a File Transfer Protocol, meant to transfer large files over TCP from one host to another. FTP supports both clear-text sign-in authentication, and anonymous sign-in. There are various FTP clients available for download, both free and paid.
DNS: Domain Name System is used to translate human readable names of addresses (like web addresses) into their corresponding IP-Addresses. These mapping are maintained in a distributed database in systems known as DNS servers.
DHCP: Dynamic Host Configuration Protocol is a protocol used by computer systems to automatically obtain IP address over a network. It does this by maintaining a small database of connected systems.
SMTP: Simple Mail Transfer Protocol is used for sending email from one host to another. It operates on port 25 for email delivery, and port 587 for new submissions from applications. Generally, port 25 is blocked for direct access from applications to prevent against abuse.
POP: While SMTP is for sending emails, POP (Post Office Protocol) is used to retrieve emails from the server to the local email client. This is useful when using email clients like Outlook or Thunderbird, and not when using your web browser to check email from one of the email sites, like gmail.com.
IMAP: Internet Message Access Protocol is a relatively newer protocol when compared to POP, and is used to retrieve emails from mail server to local client. IMAP offers several advantages over POP, for example, downloading only header and not the full message unless required, thus saving bandwidth and time, multiple client connection to the same mailbox, server side searches etc.
SOCKS: Finally in this list is SOCKS which provides access between client and server when proxies are involved. For authentication while connecting to proxy, SOCKS5 is used. One use of SOCKS is to allow connections to be made through a firewall. You would generally find this protocol extensively used in schools, colleges and offices. It is also known as SOCKetS.