What is the major responsibility of datalink layer

In Layer 2 devices, networks are viewed as logical topologies. It is responsible for transporting data over a physical link in a reliable manner. It formats the data into frames. Data link specifications include frame sequencing, flow control, synchronization, error notification, topology, and addressing. This layer converts bits into frames upon receiving information from the physical media. It consists of switches and bridges. Due to its complexity, this OSI layer is divided into three sublayers by the IEEE. The logical link sublayer governs communication between devices in the upper layer.

The middle layer is defined as the bridging layer in IEEE 802.1. Media Access Control is the lowest layer, which manages protocol access to the physical layer and ultimately to the media. Each system connected to a common data link layer has its own unique address. Its responsibility is to ensure that frames do not exceed the maximum transmission unit (MTU) of the physical media. Additionally, it identifies and corrects errors. It’s used to uniquely identify network devices and is in charge of flow control. Layer 2 addresses include MAC addresses, which are 48-bit addresses assigned to the network interface card (NIC) of a device.

MAC addresses are represented in hexadecimal notation (for example, AAAA.BBBB.CCCC). 24 bits of the 48-bit address are vendor codes. The IEEE Registration Authority assigns unique vendor codes to manufacturers. You can identify the manufacturer of a networking device based on the first half of its MAC address at https://standards-oui.ieee.org/. The last 24 bits of a MAC address are assigned as a serial number by the device manufacturer. MAC addresses should never be identical. When numerous devices are connected to the network, a strategy is needed to decide when a device sends the data. Otherwise, multiple devices could transmit at the same time and interfere. In the event that a device on a network receives a message from another device on the network, that device can provide feedback to the sender in the form of an acknowledgement message. The datalink layer uses flow control and error control mechanisms. By using flow control, it is possible to limit the amount of data that a sender is able to send at one time. This prevents the sender from overburdening the receiver with information. The error control mechanism allows the recipient of data to indicate to the sender if the expected data frame has not been received or if it has been received but has been corrupted. By computing a checksum of the received data, the recipient determines whether the data frame is corrupt. The recipient of the data can determine that the data frame is corrupt if the calculated checksum does not match the checksum received with the data frame and can then notify the sender for further action.

Written by pramod