Open Systems Interconnection (OSI) Model

The Open Systems Interconnection (OSI) Model is a conceptual model created by the International Organization for Standardization that allows various communication systems to communicate using standard protocols. In simpler terms, the OSI provides a standard for different computer systems to be able to communicate with each other. The OSI Model can be seen as a universal language for computer networking. It’s based on the concept of splitting up a communication system into seven different layers, each one stacked upon the last.

Each layer of the OSI Model handles a specific job and communicates with the layers above and below itself. The OSI model is designed to be robust, error correcting, and efficient.  However, sometimes hackers attempt to break individual communications at various layers of the OSI Model.  Often they attempt this with a DDoS attacks which target specific layers of a network connection; application-layer attacks target layer 7 and protocol layer attacks target layers 3 and 4.

Seven Layers of the OSI Model

1 – Physical Layer

The lowest layer of the OSI Model electrically or optically transmits raw unstructured data bits across the network from the physical layer of the sending device to the physical layer of the receiving device. It can include specifications such as voltages, pin layout, cabling, and radio frequencies. At the physical layer, one can find ‘physical’ resources such as network hubs, cabling, repeaters, network adapters, or modems.

2 – Data Link Layer

At the data link layer, directly connected nodes are used to perform node-to-node data transfer where data is packaged into frames via MAC addresses. The data link layer also corrects errors that may have occurred at the physical layer.

3 – Network Layer

The network layer is responsible for receiving frames from the data link layer and delivering them to their intended destinations based on the IP addresses contained inside the frame. This layer finds the destination by using logical addresses, such as IP (internet protocol). At this layer, routers are a crucial component used to route information where it needs to go between networks.

4 – Transport Layer

The transport layer manages the delivery and error-checking of data packets. It regulates the size, sequencing, and ultimately the transfer of data between systems and hosts. One of the most common examples of the transport layer is TCP or the Transmission Control Protocol.  Segmentation of packets occurs at the transport layer to ensure efficient packet deliveries that are neither to large (overcapacity) or too small (inefficient).

5 – Session Layer

The session layer controls the conversations between different computers. A session or connection between machines is set up, managed, and termined at layer 5. Session layer services also include authentication and reconnections.

6 – Presentation Layer

The presentation layer formats or translates data for the application layer based on the syntax or semantics that the application accepts. Because of this, it at times also called the syntax layer. This layer can also handle the encryption and decryption required by the application layer.

7 – Application Layer

At this layer, both the end user and the application layer interact directly with the software application. This layer sees network services provided to end-user applications such as a web browser or Office 365. The application layer identifies communication partners, resource availability, and synchronizes communication.

What does this mean for an SMB or MSP?

It’s important for your MSP or IT staff to know what the OSI Model is and how it handles information. Security-wise, within certain layers like Layer 2 and Layer 3, additional security measures can be put into place, including VLANs or PVLANs. However, the OSI Model is meant to guide technology vendors and developers so the digital communications products and software programs they create can operate together. The OSI Model provides a clear framework that describes the functions of a networking or telecommunications system that’s in use.

Additional Cybersecurity RecommendationsThese recommendations below will help you and your business stay secure with the various threats you may face on a day-to-day basis. All of the suggestions listed below can be gained by hiring CyberHoot’s vCISO Program development services.

1. Govern employees with policies and procedures. You need a password policy, an acceptable use policy, an information handling policy, and a written information security program (WISP) at a minimum.
2. Train employees on how to spot and avoid phishing attacks. Adopt a Learning Management system like CyberHoot to teach employees the skills they need to be more confident, productive, and secure.
3. Test employees with Phishing attacks to practice. CyberHoot’s Phish testing allows businesses to test employees with believable phishing attacks and put those that fail into remedial phish training.
4. Deploy critical cybersecurity technology including two-factor authentication on all critical accounts. Enable email SPAM filtering, validate backups, deploy DNS protection, antivirus, and anti-malware on all your endpoints.
5. In the modern Work-from-Home era, make sure you’re managing personal devices connecting to your network by validating their security (patching, antivirus, DNS protections, etc) or prohibiting their use entirely.
6. If you haven’t had a risk assessment by a 3rd party in the last 2 years, you should have one now. Establishing a risk management framework in your organization is critical to addressing your most egregious risks with your finite time and money.
7. Buy Cyber-Insurance to protect you in a catastrophic failure situation. Cyber-Insurance is no different than Car, Fire, Flood, or Life insurance. It’s there when you need it most.

All of these recommendations are built into CyberHoot the product or CyberHoot’s vCISO Services. With CyberHoot you can govern, train, assess, and test your employees. Visit CyberHoot.com and sign up for our services today. At the very least continue to learn by enrolling in our monthly Cybersecurity newsletters to stay on top of current cybersecurity updates.

To learn more about the Open Systems Interconnection Model, watch this short 5-minute video:

Sources: 

Cloudflare

ForcePoint

Additional Reading:

Secure Your Business with a Human Firewall

Related Terms:

Layer 2 Network

Layer 3 Network

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