The Open Systems Interconnection (OSI) Model in Action

What is the OSI model? — OSI stands for Open Systems Interconnection. It’s a conceptual framework that splits the functions of a networking system into 7 layers that are easy to understand. 
The Seven OSI Layers — The layers include the Physical Layer, Data Link Layer, Network Layer, Transport Layer, Session Layer, Presentation Layer, and lastly, the application layer. 

Let’s explore email, which lives in the Application Layer of the OSI model, to get a better idea of how all the layers come together. To find out all of the layers of the OSI Model, click here (backlink)

Unless you’re an administrator or IT professional, you likely won’t be thinking of the OSI model all too often, but it’s good information to know of regardless. Because of the way the OSI model distinctly separates the technical work across different layers, it makes it easier to isolate and troubleshoot the issues plaguing your network connection. 

It also allows administrators and IT professionals to determine what type of software and hardware to use and informs manufacturing so that they’re able to create devices that can communicate with other devices built with the OSI model in mind. It’s also just a secure model for transmitting data. 

How to troubleshoot a network issue using the OSI model

Unsurprisingly, most issues that plague network connections happen at the Physical Layer, Data-Link Layer, and Network Layer. For this reason, a good rule of thumb is to start your investigation here before proceeding to the other layers. 

  1. Check to see that all physical devices related to your network are plugged in and working; it’s not uncommon that damaged cabling is the culprit of network problems. If you have a wireless connection to your network, the cause of the problem is likely to be excessive signal attenuation or wireless interference. 
  2. If all your physical components are working properly and you’re still experiencing issues, it’s time to check the Data Link Layer. You can do so by verifying that all the VLAN and switch configurations are working properly; if those are good, move on to see if there are IP address conflicts—try to remove any duplicate IP addresses. Next, check the STP to make sure it’s functioning properly.
  3. Moving onto the Network Layer, this is where most routing and network addressing issues live. Make sure that your networking devices are not damaged, have the wrong configurations, are authenticated, and that you have enough network bandwidth. 
  4. At the Transport Layer, network issues typically come from ports that are damaged or blocked. Disabling quality of service (QoS) may resolve the issue, but otherwise, you’ll want to make sure that none of your firewalls are blocking TCP/UDP ports. 
  5. It’s rare that the network issue originates from the Session and Presentation layers because they play a less crucial role in keeping the network up and running. 
  6. Finally, at the Application Layer, you’ll find that network issues are often related to the DNS, most of which can be fixed by using the “nslookip” command. You can also try using the “tcpdump” command, which filters TCP/IP packets and analyzes network packages.

The broader impact of the OSI model 

Some argue that the OSI model is obsolete because of its more theoretical layer, but because the model helps frame discussions of protocol and helps contrast various technologies, it’s likely to remain relevant for a long time to come. 

Managing your business’s Network Services

Understanding the OSI model can certainly help with DIY network troubleshooting, but that’s probably not a responsibility you want to deal with on top of managing the day-to-day of your business. 

While it’s great to be able to handle your own network troubles, why not off-load that task to us with our Network & Wireless Connections service? 

After all, a functioning network is a crucial component of your business’s IT security. Your network is the primary piece of infrastructure that facilitates access and delivers connectivity to all your servers, files, devices, and more. 

We’ll take a close look at your unique situation to come up with a working solution that fits the way you do business. Click here for a free consultation: