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barbiauthorLayer Two OSI: A Guide to Understanding Layer Two OSI Protocols
The Open Systems Interconnection (OSI) model is a framework that describes the communication between devices in an open systems environment. It is divided into seven layers, with each layer responsible for specific tasks involved in the transfer of information. Layer two of the OSI model, also known as the data link layer, is responsible for establishing and maintaining connections between devices and for providing data connectivity between those devices. In this article, we will explore the functions of the data link layer and the protocols that are associated with it.
Function of the Data Link Layer
The data link layer is located between the physical layer and the network layer in the OSI model. Its main function is to ensure that data is properly formatted and transmitted across the network. The data link layer also handles error detection and correction, as well as establishing and maintaining connections between devices.
Protocols Associated with the Data Link Layer
1. Logical Link Control (LLC)
The LLC protocol is responsible for setting up and managing point-to-point connections between devices. It also provides error detection and correction capabilities, ensuring that data is transmitted accurately and without errors. The LLC protocol uses the SNAP (Subnetwork Access Protocol) header to identify the data being transmitted and the LLC overlay to manage the connection between devices.
2. Mediation Layer (MED)
The mediation layer is a protocol that enables devices to communicate with each other, even if they are using different data link protocols. It provides a common interface for devices to exchange data, ensuring that the data can be interpreted and understood by all participating devices. The MED protocol is used when multiple data link protocols are in use on a network.
3. Data Link Protocols (DLP)
There are several data link protocols used in various network environments. Some common data link protocols include:
- Ethernet: A common protocol used for local area network (LAN) communication, Ethernet uses the IEEE 802.3 standard and supports various data rates and media types, such as copper cables and fiber-optic cables.
- Wireless Local Area Network (WLAN): A wireless version of Ethernet, WLAN uses the IEEE 802.11 standard and allows devices to communicate over a wireless connection.
- Point-to-Point Protocol (PPP): A protocol used for point-to-point communication, PPP is designed to support various data link protocols and is commonly used in telephone networks and virtual private networks (VPN).
4. Network Connection Protocol (NCP)
The NCP protocol is responsible for establishing and maintaining connections between devices on a network. It handles the establishment of connections, data transfer, and the termination of connections. The NCP protocol is used between the data link layer and the network layer in the OSI model.
The data link layer of the Open Systems Interconnection (OSI) model is responsible for establishing and maintaining connections between devices and providing data connectivity between those devices. The protocols associated with the data link layer, such as the LLC, MED, DLP, and NCP protocols, enable devices to communicate effectively and accurately transfer data across a network. Understanding the functions of the data link layer and the protocols associated with it is essential for managing and maintaining effective communication in open systems environments.