7 Layers of OSI Model Explained: Purpose and Functions

The OSIs Model, or Open Systems Interconnection, is a conceptual model that describes the functions of a networking system and how data travels between two endpoints. It includes 7 layers of OSI model, each with its protocol and purpose. Understanding how the OSI layer works together can help us better understand modern network systems’ intricate details and workings. 

In this article, we’ll discuss the various components of the OSI layer model and how they all work together to enable network communications. We’ll also look at each layer individually and explain its role in the overall system.

What is the OSI Model?

The OSI model is a layered framework that helps network architects and engineers visualize how data is transmitted over a network. It consists of seven layers stacked upon each other in order from the lowest to the highest level. Each OSI layer has its protocols and functions, which enable communication between two endpoints on different networks. 

A Cloud engineering course can help you understand the OSI model and its layers. The OSI Layer Model was designed to provide a set of protocols that would be used consistently across different networks, allowing for greater compatibility between systems. 

Let’s deep dive into the difference OSI layer models in detail:

Layer 1: Physical Layer in OSI

Purpose and functions

The Physical layer of OSI is basically the first and lowest layer in the OSI model. Its purpose is establishing, maintain, and terminate communication between two endpoints on different networks. It does this by defining the connection type (wired or wireless), medium of transmission (fibre optic cable, copper wire, etc.), signal types (analogue or digital) and electric voltages used in data transmission. The physical layer also handles issues related to synchronization and addressing at the media level. In addition, it defines how devices interact with each other at a hardware level so that data can be sent between them successfully.

Hardware devices and protocols associated with the physical layer

The Physical layer in OSI involves several hardware devices, such as modems, multiplexers, repeaters, and transceivers. The protocols used at this layer include Ethernet (IEEE 802.3), Token Ring (IEEE 802.5), High-Level Data Link Control (HDLC) and Point-to-Point Protocol (PPP).

Common problems that can occur at the physical layer

Common issues at this layer of OSl include signal interference caused by electrical noise or radio waves; improperly configured hardware devices; incorrect cable types or lengths; and faulty connections between two endpoints on different networks.

Layer 2: Data Link Layer in OSI

Purpose and functions

The Data Link Layer provides reliable data transmission over a physical communication link. It handles the physical addressing of each node and ensures that data is properly transferred between two connected nodes on a network. This OSI layer also defines how the network will handle data errors, retransmitting lost packets, and flow control mechanisms such as windowing.

Hardware devices and protocols associated with the data link layer

The Data Link Layer In OSI involves several hardware devices, such as frames, bridges, repeaters, and switches. The protocols used at this layer include Ethernet (IEEE 802.2), Logical Link Control (LLC) and High-Level Data Link Control (HDLC).

Cloud Computing Architecture and Design can help you understand the protocols used at this layer and learn the basics to build a foundation of knowledge.

Common problems that can occur at the data link layer

Common issues at the Data Link Layer in OSI include signal interference (due to electrical noise or radio waves), incorrect media types, faulty connections between two nodes, and misconfiguration of hardware devices.

Layer 3: Network Layer in OSI

Purpose and functions

This OSI Layer is mainly responsible for routing data packets from one node to another on a network. It establishes logical paths between endpoints (nodes) on a network and determines the best route for each packet to take to reach its destination. This OSI layer also handles addressing, subnetting, packet fragmentation and reassembly, and traffic congestion control mechanisms if needed.

Hardware devices and protocols associated with the network layer

The Network Layer involves several hardware devices, such as routers and gateways. The protocols used at this layer include Internet Protocol (IP), IPX, AppleTalk, and Address Resolution Protocol (ARP).

Common problems that can occur at the network layer

Common issues at the Network Layer in OSI include incorrect routing information, misconfigured routers or gateways, inefficient path selection algorithms, signal interference due to electrical noise or radio waves, and faulty connections between two nodes.

Major Advantages and Disadvantages of Cloud Computing can help you understand the protocols used at this layer. 

Layer 4: Transport Layer in OSI

Purpose and functions

The Transport Layer is primarily responsible for providing reliable end-to-end delivery of data packets across a network. It segments large data units into smaller ones (called frames) so that they can be transferred more efficiently between nodes on a network. This layer in OSI also handles the retransmission of lost or damaged packets and flow control mechanisms such as sliding windows.

Hardware devices and protocols associated with the transport layer

The Transport Layer in OSI involves several hardware devices, such as bridges, repeaters, and switches. The protocols used at this layer include Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Real-Time Protocol (RTP) and Stream Control Transmission Protocol (SCTP).

Common problems that can occur at the transport layer

Common issues at the Transport Layer in OSI include incorrect packet ordering, misconfigured routers or gateways, inefficient path selection algorithms, signal interference due to electrical noise or radio waves, faulty connections between two nodes, and inadequate bandwidth.

Layer 5: Session Layer in OSI

Purpose and functions

The Session Layer in OSI is majorly responsible for creating, maintaining, and managing the communication between two endpoints (nodes) on a network. It establishes logical (virtual) connections between host systems, coordinates data exchange between nodes, handles token-passing mechanisms to control access to shared resources on a network, and provides security measures such as encryption for data integrity.

Hardware devices and protocols associated with the session layer

The Session Layer involves several hardware devices, such as routers or gateways. The protocols used at this layer include Network File System Protocol (NFS), Remote Procedure Call (RPC), and Secure Shell (SSH).

Common problems that can occur at the session layer

Common issues at this OSI Layer include incorrect packet ordering, misconfigured routers or gateways, signal interference due to electrical noise or radio waves, faulty connections between two nodes, inadequate bandwidth, and lack of data integrity.

Types of Cloud Service Models and Deployment Models are useful resources to help you understand the protocols used at this OSI layer. The overview will help you understand the fundamentals and their interconnections.

Layer 6: Presentation Layer in OSI

Purpose and functions

The Presentation Layer in OSI is for converting data from one format to some other so that it can be understood by both endpoints (nodes) on a network. It translates application data sent across a network into an agreed-upon format and compresses it if needed to reduce overall transmission time. This layer in OSI also provides security measures such as encryption to ensure data integrity.

Hardware devices and protocols associated with the presentation layer

The Presentation Layer involves several hardware devices, such as switches and routers. The protocols used at this layer include Hypertext Transfer Protocol or HTTP, Simple Mail Transfer Protocol or SMTP, Secure Sockets Layer (SSL) and Transport Layer Security (TLS).

Common problems that can occur at the presentation layer

Common issues at the Presentation Layer in OSI include incorrect data format, misconfigured routers or gateways, inefficient path selection algorithms, signal interference due to electrical noise or radio waves, faulty connections between two nodes, and lack of data integrity.

An introduction to Cloud Computing Deployment Models and Service Models is a great resource to help you understand the protocols used at this layer. It will help give you an in-depth understanding of the basics and how they function together. 

Layer 7: Application Layer in OSI

Purpose and functions

The Application Layer provides services to end-users, such as file transfer, web browsing, email, and chat. This OSI layer can also provide access to network resources, such as databases and printers.

Hardware devices and protocols associated with the application layer

The Application Layer in OSI involves several hardware devices, such as servers and gateways. The protocols used at this layer include Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP) and Secure Sockets Layer (SSL).

Common problems that can occur at the application layer

Common issues at the Application Layer include incorrect data format, misconfigured routers or gateways, inefficient path selection algorithms, signal interference due to electrical noise or radio waves, faulty connections between two nodes, and inadequate bandwidth.

With the various types of Cloud Computing Deployment Models and Service Models available, it cannot be easy to understand the protocols used at this layer. To understand the fundamentals and how they work together, consider familiarizing yourself with an introduction to Cloud Computing Deployment Models and Service Models. This will give you an overall overview of the various aspects of cloud computing. 

Comparison of the 7 Layers of OSI Model

Let’s look at the comparison of 7 layers of OSI Models in details here;

Common problems that can occur at the application of OSI Layer

These are some the common problems can occur during the applications of OSI layers:

• Misconfigured routers or gateways
• Incorrect data format
• Inadequate bandwidth
• Signal Interference due to electrical noise or radio waves
• Faulty connections between two nodes
• Collisions in a network
• Inefficient path selection algorithms.

Conclusion

In this guide we have learned about the OSI layers, major types of OSI Layers in detail. The OSI Layers model is an important tool for understanding the various layers of a communication network. Each layer has its function and protocols, which help enable successful data transfer between two systems. Common problems that can occur at each layer include misconfigured routers or gateways, incorrect data format, inadequate bandwidth, signal interference due to electrical noise or radio waves, faulty connections between two nodes, collisions in a network and inefficient path selection algorithms. Learning the functions of each layer is important for diagnosing any issues that may arise.