This value records whether timing (clock) synchronization was required for this failed call's bearer service, per the description, chosen from notIndicated(1), required(2), or not-required(3). Calls that require(2) end-to-end timing (typical of circuit-emulation or voice-style traffic over ATM) are more sensitive to certain network conditions than calls where timing is not-required(3), so this field helps an admin judge whether a failure is more likely tied to timing/clock-related network issues versus general bandwidth or routing problems. A pattern of failures concentrated among required(2) calls would point toward checking clock synchronization health on this port's ATM interface.