Link protocol, an aspect of communications, is the transmission process of data units between nodes. It ensures that the amount of data one computer sends is the same amount of data that another computer will receive. There is also the insurance that it is the same kind of data that was previously sent. Link protocol is one part of a model of layers called Open System Interconnection (OSI), where it is classified under the second layer.
There are seven defined layers that have become the standardized model for the architecture of computer networks. In no particular order, these seven layers consist of application, session, presentation, transport, data-link, physical layers, and network. Link protocol falls under layer two, which is also considered a layer for data-link. On this layer, data transmission occurs in the network and across some kind of physical layer, whether that is a cable, router, airwave, or LAN card. The data transfers between nodes, often on a smaller area network.
The second layer also corresponds to the TCP/IP model of reference, which is a framework of computer network protocols that evolved from the world’s first wide area network (WAN). The link protocol also evolved from this model, becoming the protocol for the second layer in a network. This layer performs procedural and functional operations for data transmission between entities within a network. It may also provide detection and correction of errors that can potentially occur at the lower physical layer of a network.
There are three techniques for flow control on the second layer. One of these techniques is a simple type of method called an automatic repeat request (ARQ), which sends a single frame of data at one time. It only sends another frame when and if it receives confirmation that the previous frame was received. Another ARQ that is used sends groups of data frames, specified by window size, without the need to receive confirmation from a receiver. The last type of ARQ is a process that sends data frames repeatedly, even if data is lost.
Layer two is distinguished because it is one layer below the network layer, which includes the WAN and the Internet. Data transmissions that occur on the second layer can either go to the Internet or be contained in the WAN. Common places for data transmission to happen only within a network include offices, school networks, and public Wi-Fi spots. The link protocol of this layer is a beneficial because if a user transmits sensitive information, such as credit card information or a social security number, it stays within the network and is more secure than going straight to the Internet.