TCP/IP: The Technology That Connected Different Networks

In the previous post, we learned how ARPANET demonstrated that computers could communicate over long distances by sending data in small pieces called packets. However, as more computer networks were created around the world, a new problem appeared.

Each network was built differently.

Different organizations developed their own networking technologies and communication methods. One network might use one set of rules, while another network used something completely different. Because of this, computers on different networks often could not communicate with each other.

It was similar to people speaking different languages. Even though everyone wanted to communicate, they could not understand one another.

The Need for Common Rules

To allow different networks to communicate, researchers realized they needed a common set of rules that every computer and every network could follow.

In computer networking, these rules are called protocols.

A protocol defines how data should be prepared, sent, received, and understood by another computer. If every device follows the same protocol, they can communicate successfully even if they were built by different companies or are located in different parts of the world.

The Birth of TCP/IP

During the early 1970s, computer scientists Robert E. Kahn and Vinton G. Cerf began designing a system that would allow multiple independent networks to communicate with each other.

Their goal was not to create another network. Instead, they wanted to create a way for many different networks to work together as one large network.

The result was a collection of networking protocols known as TCP/IP.

TCP stands for Transmission Control Protocol.

IP stands for Internet Protocol.

Together, TCP/IP became the foundation of the modern internet.

What Does IP Do?

Imagine you want to send a letter to a friend.

Before the letter can be delivered, you need to write the correct address on the envelope. Without an address, the postal service would not know where to deliver it.

The Internet Protocol (IP) works in a similar way.

Every device connected to a network is assigned an IP address, which acts like a unique address for that device.

When data is sent across the internet, IP is responsible for placing the correct destination address on each packet and helping it travel through different networks until it reaches the correct computer.

IP focuses on delivering packets to their destination, but it does not guarantee that every packet will arrive or arrive in the correct order.

What Does TCP Do?

This is where Transmission Control Protocol (TCP) becomes important.

When a large file or message is sent, TCP divides it into many small packets before transmission.

As the packets travel across different networks, they may take different routes. Because of this, they might arrive in a different order than they were sent.

TCP keeps track of every packet.

If a packet is lost during transmission, TCP requests that it be sent again.

Once all packets arrive, TCP places them back in the correct order and reconstructs the original data before delivering it to the receiving application.

This makes communication reliable even when network problems occur.

How TCP and IP Work Together

TCP and IP perform different jobs, but they work together.

TCP prepares the data, divides it into packets, checks that everything arrives correctly, and rebuilds the original data.

IP is responsible for addressing the packets and moving them across many connected networks until they reach the destination.

Together, they allow computers around the world to exchange information reliably.

Why TCP/IP Was So Important

Before TCP/IP, many computer networks existed, but they operated independently.

After TCP/IP was introduced, these separate networks could communicate using the same standard.

Instead of many isolated networks, they became one much larger interconnected network.

This idea of connecting networks together is where the word "internet" comes from. The term is short for "interconnected networks."

The Adoption of TCP/IP

Throughout the late 1970s, researchers tested TCP/IP on different types of computer networks.

On January 1, 1983, ARPANET officially switched to TCP/IP as its standard communication protocol.

This event is considered one of the most important milestones in the history of the internet because it allowed different networks to communicate using a common standard.

As more universities, government organizations, businesses, and eventually homes adopted TCP/IP, the internet grew rapidly.

TCP/IP Today

Although the internet has changed dramatically since the 1980s, TCP/IP remains one of its core technologies.

Every time you visit a website, send an email, stream a video, download a file, or use an online application, your device uses TCP/IP to communicate with servers around the world.

Many newer protocols have been developed for specific purposes, such as HTTP, HTTPS, SMTP, DNS, FTP and SSH but they still operate on top of the TCP/IP foundation.

Without TCP/IP, the global internet as we know it would not exist.

Other Networking Protocols and Models

Although TCP/IP became the standard for the internet, it was not the only networking technology developed. Over the years, engineers created several other protocols and networking models for different purposes. Some are still widely used today, while others are mostly of historical importance.

OSI Model (1984)

The Open Systems Interconnection (OSI) model was introduced by the International Organization for Standardization (ISO) in 1984.

Unlike TCP/IP, the OSI model is not a protocol used to send data over the internet. Instead, it is a conceptual model that explains how network communication works by dividing it into seven layers.

These layers are Physical, Data Link, Network, Transport, Session, Presentation, and Application.

The OSI model is mainly used for learning, teaching, designing networks, and troubleshooting network problems. In real-world internet communication, TCP/IP is used instead of the OSI model.

FTP (File Transfer Protocol)

FTP was first standardized in the early 1970s, before TCP/IP became the internet standard. After TCP/IP was adopted, FTP was updated to work over TCP/IP networks.

FTP is used to transfer files between computers over a network. For many years, it was one of the most common ways to upload files to web servers.

Today, FTP is used much less because it does not encrypt data, making it less secure. More secure alternatives such as SFTP (SSH File Transfer Protocol) and FTPS (FTP Secure) are now commonly used.

SMTP (Simple Mail Transfer Protocol)

SMTP was introduced in 1982.

It is responsible for sending emails from one mail server to another. Whenever you send an email, SMTP is usually involved in delivering it.

SMTP is still widely used today and remains the standard protocol for sending email across the internet.

POP3 and IMAP

POP3 was introduced in 1988, while IMAP was developed during the 1980s and later standardized in the 1990s.

Both protocols are used to receive emails.

POP3 typically downloads emails from the server to a device, while IMAP keeps emails synchronized across multiple devices, allowing users to access the same mailbox from a phone, tablet, or computer.

Today, IMAP is more commonly used because it works better with modern cloud-based email services.

HTTP and HTTPS

HTTP (Hypertext Transfer Protocol) was introduced in 1991 as part of the World Wide Web.

It is the protocol used by web browsers and web servers to exchange web pages.

HTTPS, introduced in the 1990s, is the secure version of HTTP. It encrypts communication between a browser and a website, helping protect passwords, payment information, and other sensitive data.

Today, nearly all websites use HTTPS instead of HTTP.

DNS (Domain Name System)

DNS was introduced in 1983.

It translates human-readable domain names such as example.com into numerical IP addresses that computers use to locate each other on the internet.

Without DNS, users would have to remember the IP address of every website they wanted to visit.

DNS is still an essential part of the modern internet.

SSH (Secure Shell)

SSH was introduced in 1995.

It allows users to securely connect to and control remote computers over a network.

System administrators, developers, and cloud engineers frequently use SSH to manage servers from anywhere in the world.

Why TCP/IP Became the Standard

Many internet protocols, including HTTP, HTTPS, FTP, SMTP, DNS, and SSH, actually run on top of TCP/IP. They do not replace TCP/IP. Instead, they rely on TCP/IP to transport their data across networks.

TCP/IP acts as the foundation of internet communication, while higher-level protocols perform specialized tasks such as transferring files, sending emails, loading websites, or connecting securely to remote computers.

This layered approach is one of the main reasons the internet can support so many different services while still using the same underlying networking technology.