THE TOPOGRAPHY OF NETWORKING
How do computers talk to each other over networks and the internet? The answer is through the TCP/IP model. TCP (Transmission Control Protocol) is the method used by computers to connect over networks, while IP (Internet Protocol) is the way in which data is transferred using ‘packets’ of information. This model can be broken down into four component layers: Application, Transport, Internet and Network Access.
At the top is the Application layer, which splits into three basic elements. At the very top sit the programs you use to access the internet, such as your email client. Beneath this is the ‘presentation’ element, where data is translated into a suitable format for sending over the network — if it needs compressing or encrypting, that happens here. Then there’s the ‘session’ element, which determines the type of connection — or session — that’s established between you and the remote computer. Examples include HTTP/HTTPS for connecting to websites and servers, FTP for basic file transfers, and SMTP for email.
Beneath this is the Transport (TCP) layer. This manages how the data is delivered, by converting it into ‘packets’ for sending, then making sure they’re safely delivered, and reassembled at the other end in the correct order. It also works in reverse for packets received by your computer.
The third layer is the internet (or network) layer. This is the layer that covers how the data is addressed and then routed between different devices. It’s also where the actual delivery of data occurs, using IP packet-switching.
The final, bottom layer is the Network Access (or Network Interface) layer. This is where error detection and correction take place as the data is packaged and transported, plus it’s where you’ll find the physical hardware — typically Ethernet or Wi-Fi — that connects you to your network and the internet.