Sending the Photo
Let's assume you're using a messaging application on your desktop device. These devices are called End Systems because they are at the edge of communication in a network, meaning they are responsible for sending and receiving information. Examples include smartphones, desktop computers, laptops, and even modern refrigerators. Let's also assume that your device already has the stored IP address of a particular friend. The IP address works like your friend’s home address because it guides the message to its final destination.
Generally, our devices are connected to a Wi-Fi network or, in the case of a computer or laptop, to an Ethernet cable. These two terms refer to two different link technologies. Links are the connections that link one internet component to another. Both Wi-Fi and Ethernet are local links, meaning they are used within local area networks (LANs).
Once this connection is established and you send the photo, the first thing that happens is that your device breaks the image into multiple smaller packets. Each packet, in addition to containing the delivery IP address, also includes important information that allows the image to be reassembled correctly on the other end, like a series of numbered envelopes. This process is similar to mailing a letter but splitting it into multiple parts.
The Beginning of Traffic
Let’s assume you are connected using an Ethernet cable. This cable is usually plugged into your local router, and data is sent to this router through the Ethernet connection. Routers then forward this data to your ISP (Internet Service Provider). ISPs are the companies that connect users to the global internet, usually charging a fee for the service.
These ISPs have a network of switches and links. They are usually cable TV or telephone companies. In this example, let's consider a cable TV company as the ISP. When your image packets leave your router, they start traveling through the ISP’s long coaxial cable to a distribution terminal. There, as mentioned earlier, there is a network of switches and links.
Switches
Switches are network devices that receive, process, and forward data packets to the correct destination within a network. They function like traffic intersections, efficiently directing the flow of information.
Entering the Internet
When the packets reach the ISP's router, it analyzes the IP address. Every router has something called a forwarding table, which determines the best route the packet should take, meaning which link it should follow. Once this is determined, the packets are forwarded through that link.
At this stage, some issues you might have heard of can occur, such as queue delay or packet loss.
Routers have a component called a buffer, which acts like a waiting queue for packets. The buffer temporarily stores packets when the network is congested, helping to prevent immediate data loss. It regulates the flow of packets, gradually releasing them as the network clears up. This is essential to maintaining data integrity during high traffic. However, if the buffer becomes completely full, some packets may be discarded to free up space, leading to packet loss.
Wow, All This Just for a Single Photo?
Afterward, the link forwards these packets to another router, which has its own forwarding table, repeating the process until they reach your friend's ISP. Once there, the ISP forwards the packets according to its own forwarding table until they finally reach your friend’s home.
Your friend's device, using the same protocol that assembled the packets (TCP), reconstructs them, and voilà, the image appears on their screen. The TCP protocol ensures that all packets arrive in the correct order and without errors.
Therefore, the internet can be defined as the interconnection of end systems (or devices), switches, and links. Additionally, protocols play a crucial role in this interconnection by defining the rules and standards that allow efficient communication between different devices and networks.
Extra: Layered Protocols
This explanation shows that the internet is simpler than it seems. However, it consists of multiple technologies and layers. Each layer has a specific protocol. A protocol is simply the way we communicate, meaning a set of rules defined for sending and receiving data.
On the internet, each layer has a specific protocol that must be followed. Below are some examples of these layers and their respective protocols. You can research them further for a deeper understanding. In future content, I will provide detailed explanations of each internet layer.
Layers and Their Protocols
- Application Layer: HTTP, SMTP, FTP
- Transport Layer: TCP, UDP
- Network Layer: IP
- Link Layer: Ethernet, Wi-Fi
- Physical Layer: Copper wires, Fiber optics, Radio waves
Each of these layers works together to ensure that your photo is transmitted correctly and securely. For example:
- The Application Layer prepares the image for sending.
- The Transport Layer divides the image into smaller packets and ensures they reach the destination correctly.
- The Network Layer determines the best route for these packets to travel across the internet.
- The Link Layer manages the transmission of packets between devices within the local network.
- Finally, the Physical Layer is responsible for the physical medium that carries the data, such as cables or radio signals.
This layered system is what makes the internet reliable, scalable, and efficient in delivering data, whether it's a simple text message or a large image file.
This explanation provides a simple and didactic overview of how the internet works when sending a photo. I hope it helps clarify the different components and processes involved! 🚀
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