What is the OSI Model? OSI Layers and Their Functions

OSI, short for Open Systems Interconnection, is a reference model that defines how communication occurs in computer networks. Developed by the ISO (International Organization for Standardization), the primary objective of the OSI model is to ensure seamless communication between hardware and software from different vendors by adhering to a common standard. Let’s explore the OSI model layers and their key characteristics in more detail.

The 7-layer OSI model standardizes communication between devices and software within computer networks. It enables systems, devices, and applications from different manufacturers to communicate using a common language. The OSI abbreviation stands for “Open Systems Interconnection.” Another way to answer the question “What is OSI?” is: the OSI model is a theoretical framework that segments network communication into layers, simplifying management. From a business perspective, OSI plays a strategic role beyond its technical framework—it impacts areas such as cybersecurity, customer experience, cost optimization, and business continuity.

Key OSI model features include:

• The OSI model defines communication in 7 distinct layers, from the physical medium up to the application layer. Each layer has a specific role and operates independently.
• It enables interoperability between hardware and software from different vendors.
• As a globally recognized reference model, it ensures universal applicability.
• By breaking down complex network communication into manageable layers, each layer can function independently, meaning changes in one layer don’t impact others.
• Each layer communicates directly only with the layer above and below it, which facilitates easier troubleshooting and maintenance.
• The layered structure helps identify issues efficiently. For example, if internet access is unavailable, the issue could be pinpointed to the physical cable (Layer 1), IP address (Layer 3), or application (Layer 7).
• New protocols, devices, and technologies can be developed to comply with the OSI framework.
• Security strategies can be implemented layer by layer.
• The OSI model is compatible with modern networking technologies.

The OSI model layers shown in the table represent the structure that explains how computer networks function. The answer to “What are the OSI layers?” is: physical, data link, network, transport, session, presentation, and application layers. In total, the OSI model has 7 layers, each with its own responsibilities. Data flows from the top layer downward. Layers 1 to 3 manage data transmission; Layers 4 to 6 organize the communication process; Layer 7—the Application Layer—delivers services to users.

The OSI model facilitates a layered approach to troubleshooting, enabling faster diagnosis and resolution of network problems. For instance, if email delivery is delayed, the OSI layer model can help identify whether the issue lies in physical infrastructure, routing, or the application itself. The functions of OSI layers are essential for applying secure communication protocols. The presentation and application layers handle encryption and secure delivery of data, helping organizations protect customer information, meet compliance requirements, and maintain reputation. Since OSI is used as a reference by vendors, businesses can integrate multi-vendor systems seamlessly and optimize their infrastructure investments. The OSI layers and protocols enhance business processes through fast data transmission, secure session control, and smooth application access—boosting employee productivity and customer experience. The network and transport layers support secure and reliable VPNs and branch connectivity, ensuring uninterrupted remote and multi-site operations. The OSI model’s 7-layer structure underpins compliance with data protection laws such as KVKK and GDPR. Looking to provision all your IT infrastructure as a fully managed service? Learn more about GlassHouse's Infrastructure as a Service (IaaS).

As a globally adopted model that defines network communication in seven layers, the OSI model is not just a technical standard—it is a blueprint for network security, efficient data transmission, problem resolution, and cross-platform compatibility. Understanding and implementing the OSI model effectively ensures seamless communication, regulatory compliance, and a competitive edge. Interested in managing your OS inventory securely and efficiently with GlassHouse’s expert team? Discover more about our Operating System (OS) Management Services.