This series adopts the Rapid Link Detection Protocol (RLDP), a link detection protocol incorporated by Data General for rapid detection of Ethernet link failures.
Most Ethernet link detection mechanisms detect link connectivity by automatically negotiating the physical layer based on the state of the physical connection. However, this type of link detection mechanism has certain limitations. In some cases, it cannot provide users with reliable link detection information. For example, when the Tx and Rx ends of a fiber optic cable are incorrectly connected to an optical port, due to the existence of a fiber optic converter, the link at the port is still physically active, but in reality the communication at layer 2 link is off. Another example is that if there is an intermediate network between two Ethernet devices, due to the existence of a relay device on the network, the same problem will occur if the relay device fails.