ATM - Asynchronous Transfer Mode is an advanced version of a packet switching network. ATM uses digital technology to transmit 53 byte cells instead of frames of differing lengths. ISDN - Basic Rate ISDN is divided into two 64 Kb channels and one 16 Kb channel. The 64 Kb channels are the B channels and carry voice or data. The 16 Kb channel is the D channel and is used for link management.
Traffic only flows on one of the rings unless the primary ring is broken.
In this case, the second ring will take over providing fault tolerance. Beaconing is used on a FDDI network to isolate network failures. Beaconing is when one computer detects a fault and sends out a beacon. The computer will continue to send the beacon until it hears a beacon from an upstream computer. Digital Volt Meters - Can determine if the cable is able to carry network traffic or if the cable is broken.