7 Layers of Network Communication
In late 2019 we covered internet connectivity for laypeople, which we divided up into three sections (see here, here, and here). This blog will follow a similar course, but this time we are going to focus on the supposed seven layers of technology that undergirds communication between devices in the network.
Seven layers…communication…networks, “that’s already too complicated for me” one might be thinking. While the topic of network communication might seem intimidating, we hope this blog will simplify it for both laypeople and IT people alike. Once you know the high level of computing that goes into merely sending an email, you’ll have a newfound appreciation for everything IT.
Overview
The seven layers to technology are the supposed seven layers of complexity that occurs in an OSI model (Open Systems Interconnection model). This is not tangible but rather describes the complex arrangement and movement of information in a network.
The OSI model says that every communicating device has these seven layers of function, and these layers are in use when two endpoints in a network are communicating. So when messages are sent between users all seven layers are in effect.
The seven layers are arranged in descending order with layer 7 at the top and layer 1 at the bottom. Visually, this would look like data starting at layer 7 then flowing down the layers in the source computer. This data would reach layer 1 in the source computer, travel across the network, and then reach layer 1 in the receiving computer. The data would then make its way up from layer 1 in the receiving computer until it reaches layer 7 at the top.
The Seven Layers to Network Communication
Layer 7 Application: At the top of all the layers, layer 7 enables the user to interact with applications that are on the network. Of all the layers, this is the one where you, the end-user, are closest to. The application services one uses on this layer are web browsers, e-mail, web conferencing and other network-dependent apps. Another important component of layer 7, is that it accepts the data syntax given to it by layer 6.
Layer 6 Presentation: Picking up where we left off, layer 6 translates the data syntax into something that layer 7 can make sense of. Data syntax is the code or the language of a computer. Layer 6 is just “presenting” data to the application layer because layer 7 can only determine if the data syntax is correct or needs reformatting. At this layer, data is being decoded or encoded and then tailored to fit the parameters of whichever application the data is bound for.
Layer 5 Session: Layer 5 manages communication between applications. This communication between apps needs a “session” to be created where rules are defined. These rules include setup, wait time, reconnection parameters, and closure of apps once the session ends.
Layer 4 Transport: Whereas layers 7 through 5 are translating, encrypting and then displaying that data and layers 3 through 1 are receiving and then packaging the data, layer 4 transports the data across the network. The Transport layer manages what data is being transferred between hosts and end systems. The destination, the amount of data, and the rate at which to send the data (flow control) are all managed at layer 4.
Layer 3 Network: Layer 3 focuses on moving data to other networks. This layer creates packets of data and encodes the right address on each packet so that it reaches the right destination. Layer 3 is also where the router operates. Routers narrow down the pathways your device could connect to another device and chooses the best/fastest route for the packages to travel.
Layer 2 Data Link: Layer 2 is where data packets are either decoded or encoded into bits. There are two sub-layers to the Data-link layer: The Media Access Control sub-layer controls how a computer gains access to data and manages how it gains permission to send it. The Logical Link Control sub-layer controls the copying of data accurately and in real-time; error correction of data coming up from the physical layer is also done by the Logical Link Control sub-layer.
Layer 1 Physical: Layer 1 is the electronic and mechanical representation of the system. The previous layers were all representations of software, but the Physical layer operates as hardware. The cables, SIM cards, and other physical pieces that are built into a device are found here. The prime goal of this layer is to capture the bitstream coming through the network. The bitstream contains the data but it’s broken down and sent through the network using electrical impulses, radio waves, or light signals. Check out our blog on the physical components, like coax cables and fiber, that this bit stream travels through.
Layer 1: A user at their desk accessing an application that operates on the network.
Layer 7: The physical hardware of the computer.
Summary of the Layers
That was a lot of information so let’s summarize it all in a common example you do every day: You create an email in an application like Gmail. This email is then decoded into computer data, sent to some other applications, and then prepared for transportation. The data is turned into a packet and the route is chosen. The data is then transformed into bits and then sent as an electrical signal through the network to another device.
The reverse happens when someone sends you an email: The electrical signal arrives at your computer in the form of bits. The bits are encoded into data then turned into a packet. This packet waits in a line of other data packets until it is transported to the necessary app. It may go through several sessions with other apps. Before it reaches you in the form of an email, the data is turned from computer language into what you would recognize as an email.
Still having trouble? Keep this visual in mind and read through the layers again. Think of it as either prepping an email for sending or prepping an email for reading.
Application of the OSI Model
Now with every layer established, you hopefully have a better understanding of how information is sent and received over a network. The OSI model is designed to create a convenient framework that the whole industry can reference.
Similar to how the model details network communication, it’s main purpose is to help physical communication between vendors, developers, and the inevitable 3rd parties who need to understand what they’re buying.
It’s truly a marvel once you consider all the features operating round the clock while you surf the web or text a friend. And all of this happens instantaneously too! Don’t sleep on the computing wonder that is network communication. And if you hear someone downplaying IT at a party, hit them with the seven layers of technology blog.