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The Internet is a global WAN made up of many smaller networks. These networks are owned by businesses, schools, governments, and even individuals, but they all work together by following the same set of protocols: TCP/IP. Thanks to this common suite, the Internet enables people to communicate and share information worldwide.
To understand how the internet works, it helps to break it down into components:
Every device connected to the internet needs an identifier, just as every house on a street needs a mailing address. On the internet, this is called an Internet Protocol (IP) address. An IP address is a string of numbers that uniquely identifies a device on a network.
In addition to IP addresses, every device on a local network has a Media Access Control (MAC) address. This unique hardware identifier is built into the network card and does not change. While IP addresses handle communication across the wider internet, MAC addresses identify devices within a local network.
IN CONTEXT
An IP address is like a phone number, easily reassigned. A MAC address is like a street address, tied permanently to the house where it was built.
There are two versions of the Internet Protocol because the number of connected devices grew far beyond early expectations.
IPv4 was created in the early days of the internet and uses 32-bit addresses, supporting about 4.3 billion unique values. Written in dotted decimal form (for example, 192.168.1.1), it eventually ran short as billions of new devices came online.
IPv6 was introduced to solve this problem. It uses 128-bit addresses, providing virtually unlimited unique values and offering improvements in routing, security, and mobility. IPv6 addresses are written in hexadecimal and separated by colons.
IPv4 remains common because of older systems, but IPv6 is the long-term solution.
Because there are fewer IPv4 addresses than devices, Network Address Translation (NAT) was developed to let multiple devices share a single public IP. Inside a local network, each device has a private IP, while the router translates these into one public IP visible to the wider internet.
IN CONTEXT
Think of it like an apartment building. Inside, every apartment has its own number (private IPs), but from the outside, everyone uses the same street address (the public IP). The building manager (your router with NAT) sorts out which apartment each letter belongs to. Outsiders only see the building’s main address.
IPv6 does not use NAT because it has enough addresses for every device to have its own unique public IP.
A domain name is a human-friendly label used to identify websites and resources. Instead of typing IP addresses, users enter names like www.example.com. The Domain Name System (DNS) resolves these names into IP addresses so devices can connect.
When you type a domain into a browser, your device first checks if the address is cached locally. If not, it queries a DNS resolver, which consults a hierarchy of servers until it finds the correct IP. The result is returned to your device, allowing it to connect to the website.
Caching makes future lookups faster but means that changes to domain names may take time to spread across the internet.
At the heart of internet communication is the idea of breaking information into smaller pieces called packets. Instead of sending an entire email, webpage, or video as one large block, the internet divides it into many packets. Each carries a fragment of the data along with basic addressing information so it can find its way to the destination.
IN CONTEXT
Packets are like envelopes for a long letter. Instead of mailing it whole, you send each page in its own numbered envelope. The envelopes may take different routes but all arrive and are reassembled in order.
As packets travel across the internet, they pass through routers, which forward them toward the destination based on IP addresses. Because packets can take different paths, the network is flexible and can adapt to outages or congestion.
Once packets arrive, the Transmission Control Protocol (TCP) ensures they are arranged properly and requests any missing pieces. For activities where speed matters more than accuracy, such as streaming or online gaming, the User Datagram Protocol (UDP) is often used because it skips some of the error-checking steps.
The Internet backbone is the high-capacity network of cables and routers that carry data between major regions of the world. It includes:
For the internet to function, devices must agree on how to talk to each other. These rules are enforced by multiple protocols that operate at different layers of the data transmission process.
When the Internet (or any TCP/IP based network) sends and receives data, that data moves through a four-layer process. There are different protocols that govern how each layer works.
IT034
A transmission begins at the Application layer, where the program generating the request communicates with the operating system. The protocol depends on the task: a browser uses HTTP or HTTPS for web pages, while an email client may use IMAP to receive mail or SMTP to send it. This layer is closest to the user and sets the stage for the rest of the process.
The Transport layer ensures correct delivery. TCP provides reliability with error-checking and reordering, while UDP is faster but less precise, useful for streaming or gaming.
The Internet layer manages addressing and routing using IP, whether IPv4 or IPv6. It adds the source and destination addresses so routers can forward packets toward the recipient, though it does not guarantee delivery.
The Network Access layer handles physical transmission over Ethernet, Wi-Fi, or cellular. Here, MAC addresses identify devices on the local network while switches and access points move the bits. When data arrives, it moves back up the layers in reverse until it reaches the correct application.
IN CONTEXT
IT professionals must understand the TCP/IP model to configure networks, secure systems, and troubleshoot problems. End users don’t need this knowledge since software handles it automatically, but basic awareness—such as knowing email uses SMTP or video calls may rely on UDP—can make troubleshooting easier and communication with support clearer.
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