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All About Network Protocols


What are Network Protocols?

A collection of rules, conventions, and data formats that govern how devices share data across networks is known as network protocols. In reality, without all these protocols, computer networks would not exist.

Let us first understand what is OSI Model before we deep dive into network protocols.

What is the OSI Model and How it Works?

OSI (Open Systems Interconnection) Model is a seven-layer conceptual structure that explains how a networking or telecom system works. The OSI Model illustrates how a network operates and specifies how networks interact with each other. All of the layers are self-contained, and the tasks that have been allocated to them can be accomplished on their own.

The seven layers of the OSI Model separate the communication mechanism between two network devices. Following the OSI Model, here is a diagram of the interaction of two network devices:


Network protocols separate the communication mechanism into separate tasks in every layer of the OSI Model. At each layer of the data exchange, one or more network protocols are in use.

Network Protocol Characterization

Now that you understand how the OSI model works, let’s jump into protocol classification. The protocols mentioned below are some of the most widely used in communication networks.

Application Layer Network Protocols

  • 1. HTTP (Hypertext Transfer Protocol): HTTP is a protocol that helps you access resources like HTML documents. It is the backbone of every data exchange on the Internet. It was established to communicate between web browsers and servers. HTTP Requests are used to communicate between client computers and web servers.
  • HTTP port No – 80


  • 2. HTTPS (Hypertext Transfer Protocol Secure): HTTPS (Hypertext Transfer Protocol Secure) is a safe variant of HTTP. The protocol is used to send data between your browser and the website you’re visiting. The HTTPS protocol allows website users to transfer confidential information such as credit card details, bank details, and login information over the internet in a secure manner.  What makes it secure is TLS (Transport Layer Security), and SSL (Security Sockets Layer).
  • HTTPS port no – 443


  • 3. FTP (File Transport Protocol): File Transfer Protocol is commonly used for sharing information between computers across a TCP/IP-based network, like the Internet. Users can transfer data from one system to another via FTP.
  • Port no – 21 and 20

  • 4. Telnet (Terminal emulation protocol): Telnet is an application layer protocol that allows a user to connect to a remote computer and communicate with it. Network Administrators typically use Telnet to connect and control remote computers. A Network Administrator must first input the remote device’s IP address or hostname, after which they will be provided with a virtual terminal that enables them to communicate with the host.
  • Telnet port no – 23


  • 5. DNS (Domain Name System protocol): The Domain Name System (DNS) is the Internet’s telephone book. We are using domain names to access data online. Internet Protocol (IP) addresses are used by web browsers to communicate. DNS protocol translates domain names into IP addresses.
  • Every Internet-connected device has a unique IP address that other devices use to locate it. Humans are no longer needed to memorize IP addresses because of DNS servers.

    (Example – www. Amazon.com to

    Port no – 53


  • 6. DHCP (Dynamic Host Configuration Protocol): The Dynamic Host Configuration Protocol (DHCP) is a network management protocol that assigns an IP address to any device or node on a network in order for them to communicate via IP (Internet Protocol). These settings are automated and managed centrally by DHCP. There’s no need to delegate IP addresses to new computers manually.
  • APIPA (Automatic Private IP Addressing) is an acronym for Automatic Private IP Addressing (APIPA). When a DHCP (Dynamic Host Configuration Protocol) server is unavailable, it is a feature or attribute of operating systems (for example, Windows) that allows computers to automatically configure an IP address and subnet mask.

    DHCP port no – 67, 68

  • 7: SMTP (Simple Mail Transfer Protocol): SMTP protocol enables you to send e-mail over the internet. SMTP is a push protocol for sending emails, the other side POP3 and IMAP are used to receive emails on the user end. SMTP sends the message from the sender’s device to the email server.
  • A user can use SMTP to send an email to another user on the same network or some other network.

    • Its installation is simple
    • It will connect to any device without any limitations
    • It does not require any further progress on your part

    Port no – 25


  • 8. POP and POP3 (Post Office Protocol): Post Office Protocol is also an email protocol. By using a mail server, users can download emails to their clients using this protocol. The emails can be accessed without an internet connection after they have been downloaded locally. Additionally, if the emails are transferred locally, the mail server deletes them, freeing up memory.
  • Port no – 110


  • 9. IMAP (Internet Message Access Protocol): The Internet Message Access Protocol (IMAP) is a mail protocol that allows a local user to access email on a remote web server. The two most widely used Internet mail protocols for retrieving emails are IMAP and POP3. Both current email clients and web servers accept both protocols whereas the POP3 protocol means that your email is only accessed by one application. IMAP allows several clients to view your email at the same time. This is why IMAP is a safer option if you’ll be viewing your email from different places or if your messages will be handled by multiple users.
  • Port no – 143


    Transport Layer Network Protocols

    1. TCP (Transmission Control Protocol): TCP is a transport layer protocol that provides a reliable stream delivery and virtual connection service to applications through the use of sequenced acknowledgment. TCP is a link-oriented protocol, which means that it needs to create a connection before data can be transferred. Its function is to transfer packets through the internet and ensure that data and messages are transmitted successfully across networks. During transmission, TCP dynamically divides data into packets. TCP has the ability to repair transmission errors. It will detect and restore packets that have been sent out of order.


    1. UDP (User Datagram Protocol): UDP is a connectionless transport layer protocol that offers a clear and simple but unstable message service. Just as with TCP, UDP does not have any functions for stability, flow management, or error handling. When the stability mechanisms of TCP aren’t needed, UDP comes in useful. UDP does not allow for the retransmission of missing data packets.
    • UDP allows for broadcast and multicast links.
    • TCP is slower than UDP.


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    Nikhilesh kotiyal ( )
    Infosec Train
    Nikhilesh Kotiyal has completed his degree in Information Technology. He is a keen learner and works with full dedication. He enjoys working on technical blogs. Currently, Nikhilesh is working as a content writer at Infosec Train.