What is the OSI Model?

OSI model

The Open Systems Interconnection (OSI) model is a conceptual framework that divides network communications functions into seven layers. Each layer represents a specific level of abstraction and performs specific functions related to the communication process. The OSI model helps in the understanding of how different networking protocols and technologies interact and communicate with each other.

In this article we will explore the OSI model and the importance of physical layer security. Additionally, the need for robust cybersecurity measures at the physical layer.

The Seven Layers of OSI Model

The OSI model divides a communication system’s data streams into seven distinct abstract layers. Each layer possesses its own clearly defined function, which in turn interacts with adjacent layers, collectively shaping the OSI communication protocols.

Below is an overview of the seven layers and their individual functions:

Physical Layer of the OSI Model
Seven layers of OSI Model

Physical Layer: The Foundation of Network Communication

The OSI model physical layer is where the transmission and reception of raw data take place between devices. Examples of Physical layer devices range from repeaters to hubs. Data units, such as bits, derive from energy in the form of radio waves or electricity. These units are subsequently conveyed through a physical medium, like fiber optic cables or copper wiring. Essentially, this layer manages the physical link connecting a network with its nodes.

It’s crucial to enhance security at this layer to prevent hardware based attacks

Data Link Layer: Managing Local Networks

The OSI model Data Link layer technically consists of two sub-layers. One being Media Access Control (MAC) and the other is Logical Link Control (LLC). At this layer, the system manages access to the physical layer and to local networks. Both sub-layers act and connect bridges to Layers 1 and 2.

The MAC layer transports data between itself and Layer 1, while LLC communicates with Layer 3 (LAN – Network Devices). This establishes the data link between the two sub-layers that use switches and bridges.

Network Layer: Routing Data Across Networks

The OSI model Network layer is comprised of commonly known elements, such as routers and IP addresses. On this layer, the routing of data takes place from one system connected on a LAN to another. Usually, IP protocols (IPv4 and IPv6) determine the most optimal routing paths across a physical network to ensure the delivery of network packets.

Transport Layer: Ensuring Reliable Communication

The OSI model Transport layer is where packet sequencing takes place. Breaking the transferred data into segments enables the possibility of resending or re-sequencing data packets. Layer 4 is also responsible for overall flow control and error detection. Maintaining flow control ensures a match between the rate of data being sent and the connection speed of the receiving device. Error detection confirms the accuracy of data reception. If confirmation of data receipt is lacking, error detection initiates another request to facilitate complete communication. 

The protocols used in Layer 4 are Transmission Control Protocol (TCP), and User Datagram Protocol (UDP). Both of these protocols enable different types of data transmission. TCP is known to be a more reliable method, and UDP prioritizes the speed of data transfer.

Session Layer: Managing Communication Channels

The OSI model Session layer establishes and manages communication channels between devices. Layer 5 is responsible for ensuring uninterrupted data transfer by overseeing the functionality and operation of sessions. In addition to initiating and terminating communication channels, Layer 5 also sets up checkpoints during data transfer, which can aid in resuming a session in case of interruption.

The session layer employs communication types: simplex, half-duplex, and full-duplex. Each of these represents a distinct transmission mode utilized for data communication.

Presentation Layer: Data Formatting and Encryption

The OSI model Presentation layer serves the function of receiving data and presenting it to the application layer. It accomplishes this by making the data comprehensible through processes like compression, encoding, and encryption, enabling its reception on the opposite end. 

Common concepts within layer 6 include known formats such as JPEG, GIF and TIFF.  

Application Layer: End-User Interaction

The OSI model’s Application layer represents the final interface where a user and a computer application interact. It is commonly refer to this as end-user software. Examples of protocols that take place at Layer 7 are: FTP (File Transfer Protocol), HTTP (Hypertext Transfer Protocol), and DNS (Domain Name System).  

Users interact with end-user software daily, from their web browser to instant messaging.

OSI Model and Physical Layer

The Physical Layer of the OSI model (Layer 1 visibility) is the lowest layer and provides hardware security overview. This layer is responsible for the actual physical connection between the devices by identifying the equipment involved in the data transfer. Layer 1 defines the hardware equipment, cabling, wiring, frequencies and pulses. The information exists in the form of bits and nodes transmit it from one to another.

The problem is that hardware security goes neglected. Existing security software solutions do not cover the Physical Layer of the OSI model (layer 1). Without physical layer visibility, the physical specifications of the network are not captured. Hence, network implants – Rogue Devices which operate on the Physical Layer – are not detected. Similarly, spoofed peripherals – Rogue Device manipulated on the Physical Layer – are identified as legitimate HIDs (Bad USB).

Without physical layer visibility, enterprises are at risk of Rogue Devices infiltrating their network and conducting harmful hardware attacks. As Layer 1 is the first of the OSI layers it is crucial to have adequate physical level security protection at this level, to stop the attacks originating from Rogue Devices at the very first instant.

Physical Layer of OSI Model and Sepio’s Platform

Sepio platform introduces innovative patented technology aimed to enhance the cyber security of your network organization. The Physical Layer within the OSI Model serves as the fundamental network infrastructure level where real data transmission takes place. Leveraging advanced visibility and control capabilities, Sepio effectively mitigates risks and rapidly identifies potential threats to your network. In contrast to other cybersecurity solutions that may overlook Layer 1 visibility and hardware security, Sepio places its focus on defending against threats at the Physical Layer, such as network implants, rogue devices, and malicious activities, including spoofed peripherals like malicious USB devices.

What distinguishes Sepio is its non-intrusive methodology. When deployed, the system abstains from probing network traffic or utilizing discovery protocols, ensuring that it does not monitor any proprietary data. Consequently, your organization can enjoy a straightforward and efficient implementation process.

Sepio substantially reduces the risk of employee negligence (Human Factors in Cybersecurity), bolstering your overall cybersecurity posture. Let us assist you in optimizing your security efforts and minimizing costs related to potential security breaches, thereby safeguarding your employees as your most valuable asset. Rely on Sepio for unparalleled protection at the Physical Layer of the OSI Model.

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November 22nd, 2022