How does the AppleTalk Echo Protocol determine the availability of a node?

The AppleTalk Echo Protocol determines the availability of a node by sending echo requests that prompt the node to respond. When the protocol sends out these echoes, the node that receives the request replies back to the originating device. This back-and-forth communication effectively verifies that the node is active and reachable on the network. By receiving a response, the originating device can conclude that the node is available and operational.

The process is similar to how other network protocols use echo requests to check connectivity, which aids in troubleshooting and monitoring network reliability. The focus on an active reply—essentially an 'echo' from that node—makes this method straightforward and effective for confirming the availability of devices within a network.