I am starting out in IT and am about to complete A+ cert course. I understand that TCP/IP is a foundation element of the internet and is implemented with many other protocols. I would like to know exactly what it’s function is tho. What does it do, how long has it been around, and how it work in tandem with other protocols? I’ve tried researching it but always end up reading a bunch of high level tech jargon.
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Everyone else seems to be explaining the TCP and IP protocols, which is useful, but it sounds like you’re asking about the TCP/IP model, which is a little bit different. The TCP/IP model is a high level overview of how data is processed and managed while travelling through a network. It’s split up into these layers:
Application
Transport
Network (Sometimes called the Internet Layer)
Data Link (Sometimes called the Network Access Layer)
This model is kind of a simplified version of another model, called the OSI model, which I won’t go into, but I’m sure you’ll learn about it in your course. Data is formatted in different ways as it travels through a network (or multiple networks). At each layer, the data must be handled by a device, or piece of software that knows how to manage data at that layer. I’ll use a website as an example. When you’re in your web browser, you type [youtube.com](https://youtube.com) into the URL bar, and your DNS server retrieves the IP address of the Youtube servers. Your computer needs to create a web page request that can be sent to the Youtube servers, asking them to send back the home page so your browser can display it. The creation of this request happens in the Application layer, it all happens on your local computer, and no data is sent over any network. To send your request to youtube, we move to the transport layer.
In this layer, a set of rules for the connection are established, (called the protocol). This layer describes how the data will be sent, and how it will be received. For example, the TCP protocol. Other people have explained this protocol pretty well already, but essentially, the source device and destination device must communicate with each other first before the data is sent. Then once the destination device receives the data, it must send an acknowledgement back to the source, to confirm that that data was sent successfully. There are other protocols that have different rules, such as UDP, and you can look them up if you’re interested. Once this is done, the data moves to the network layer.
This is the layer where the data is sent to devices on other networks, and is where IP addresses are used to route the data. In this layer, the data is bundled with the IP addresses of the source and the destination. This bundle is called a packet. In order for your computer to transmit data over the internet, it needs to get it to the router, and the router will handle it from there. The router is connected to the computer via an ethernet network, but ethernet devices don’t understand IP addresses, or any network layer protocol, so now the data moves to the data link layer.
Ethernet devices, such as network cards and switches aren’t addressed with IP addresses, instead they use MAC addresses. The network card and the switch don’t understand the IP addresses and the web page request inside the packet, all they understand is that they need to get that data to the router. So the data packet is bundled up again with the MAC address of the source device (your computer’s network card) and the destination device (the router). This bundle is called a frame. Your network card sends the frame to the ethernet switch, which then sends it to the router. The router deconstructs the frame and takes out the packet inside, and proceeds to send it to youtube. When the youtube server receives the packet, it deconstructs it to find the web page request inside.
Now the process happens in reverse, the youtube server gets the home page of youtube, wraps it up into a packet (network layer), and sends it to your router, the router wraps it up into a frame (data link layer) in order to send it over the ethernet network, then your computer receives it, deconstructs the frame and the packet, and finds the web page inside. Now we’re back on the application layer, and the web browser can display the web page on the screen.
This is a simplified overview, in real life, the internet is very complicated and the data will be bouncing back and forth between different layers multiple times as it passes through different networks on it’s journey to youtube.
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