The OSI Model Layers Explained

What does OSI and ISO stand for? OSI stands for open systems interconnection and ISO stands for International Organization of Standardization. It is a conceptual framework or network layer protocol that describes the different functions of a networking or telecommunication system and outlines how applications communicate throughout a network for a gateway OSI layer. An OSI layers or ISO layers description consists of seven layers which are typically described from the top to bottom. In order from seven to one, the network switch layers are as follows: application, presentation, session, transport, network, data link, and physical.

The layer 7 switch network stack provides a visual representation of what happens within a networking system for flow control. Having a good understanding of the OSI model and networking levels can help narrow down the source of networking issues, develop applications, and better understand which networking products work with which layers. To improve your understanding of thecomputer networking OSI model uses, consult this guide on the OSI model layers explained. It will help explain the OSI reference model in detail.

Layer 7: The Application Layer

The top layer of an OSI reference model (layer seven) is the application layer that delivers network services or protocols that comply with an end-user’s data to the end-user. The majority of end-users interact directly with applications that work at Layer 7. As such, it is the most widely recognized OSI layer by end-users.

Examples of Layer 7 applications include web browsers such as Google Chrome or Firefox, as well as apps such as Office, Outlook, and Skype. The services provided by each of these applications permit the application layer to supply and receive data from the Presentation layer.

Layer 6: The Presentation Layer

Also referred to as the Syntax Layer, The Presentation Layer is responsible for performing syntax processing. In this case, syntax processing typically involves converting data from the top layer (which is in application format) into network format based on the syntax that the application accepts. The Presentation Layer may also transmit data from network format to application format. Depending on whether the data is being transmitted or received, the processed data is then either passed to, or rather, “presented” to the session layer or application layer.

Layer 5: The Session Layer

The Session Layer is responsible for creating a session or connection that allows two devices, computers, or servers to communicate with one another. Once the session has been formed, the data is then passed either to or from the Transport Layer.

In addition to setting up a session, the resulting connection between the machines is also managed and terminated once the session ends at Layer 5. The Session Layer is also responsible for authentication and reconnection in the case that a network interruption occurs.

Layer 4: The Transport Layer

The Transport Layer is responsible for coordinating data transfer across network connections. It helps regulate various elements involved in data transmission between end systems and hosts. Such factors include the data packet’s size, sequencing, speed, and destination.

Once the Transport Layer has effectively managed and error-checked the data packets, the data is passed either to or from the Network Layer. Some of the most well-known examples of the Transport Layer include the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

Layer 3: The Network Layer

The primary role of the Network Layer is to handle packet forwarding which includes the routing of data. When connecting to a server, there are millions of different paths a device can take. Routers at the Networking Layer help direct data to its ultimate destination between several different networks.

To do so, the Network Layer receives frames from the data link layer and examines them to determine if the data has arrived at its intended target. Then, the Network Layer delivers the data frames to their ultimate destinations. To determine the destination of a data link, the Network Layer locates the logical address such as an internet protocol (IP) address which is contained inside of the data link. The majority of the router functionality that networking professionals enjoy is found at Layer 3.

Antaira Technologies carries several Layer 3 networking devices such as our 10 Gigabit Ethernet Switch which is equipped with pre-loaded standard Light Layer 3 network management software. Examples of our other Layer 3 devices include our 10, 12, 16, and18-Port Industrial Gigabit PoE+ Light Layer 3 Managed Ethernet Switches.

Layer 2: The Data Link Layer

Once data has passed through the Network Layer, it then arrives at the Data Link Layer. Often considered the most complex OSI model layer, the Data Link Layer is responsible for setting up links across a physical network. To do so, node-to-node data transfer is performed by nodes that are directly connected in the Data Link layer. As a result, data is packaged into frames. In addition to setting up links, the Data Link Layer also helps check for and corrects any errors that occurred at the Physical Layer before packaging the data into frames.

The Data Link Layer is composed of two sublayers known as Media Access Control (MAC) and Logical Link Control (LLC). Once the data has been packaged into frames, the Data Link Layer will direct the physical addressing methods used for these two sublayers. The MAC sublayer helps control the flow of data packets to and from one Network Interface Card to another across a shared channel in a network. The LLC layer is the upper sublayer of the Data Link Layer which serves as an interface between the network layer and the MAC sublayer.

Antaira Technologies also carries many networking switches that operate at Layer 2. Examples of our networking switches that are equipped with Layer 2 network management include our 10/100TX PoE Managed switches, Gigabit PoE managed switches, and Gigabit Low Voltage PoE managed switches. As an influx of various measurement devices is incorporated into process sections, our Layer 2 switches can help ensure successful data routing within your network.

Layer 1: The Physical Layer

The Physical layer is the lowest OSI model layer which is the physical and electrical representation of the system. It is comprised of various network components such as power plugs, wireless radio frequencies, connectors, receivers, cable types, adapters, the layout of pins, and electric voltages.

The main role of the physical layer is to electrically or optically transmit unstructured data bits from the physical layer’s source or sending device to the physical layer of the receiving device across the network. When there is an issue in a network, most troubleshooting will begin at its physical layer.

Antaira Technologies is a leading provider of industrial networking equipment such as managed and unmanaged Ethernet switches, industrial routers, media converters, and serial communication devices. Interested in a more detailed ISO OSI 7 layers explanation or you want to learn more about our network communication products and network layer protocols, contact us today. One of our experts can further discuss our data link layers to fit your application and help with error control.