What is the maximum allowed round-trip time between standard Cisco UCM nodes?

40 ms is a common latency requirement for voice media paths (one-way), but not the maximum RTT between CUCM infrastructure nodes.

Cisco Unified Communications Manager (CUCM) cluster design guidelines specify a maximum round-trip time (RTT) of 80 milliseconds between all CUCM nodes within a single cluster. This latency constraint is essential for maintaining database synchronization, ensuring call processing reliability, and guaranteeing feature functionality across the distributed CUCM system.

150 ms is typically the maximum one-way latency recommended for voice calls, not the RTT between CUCM infrastructure nodes.

500 ms is an unacceptably high latency that would severely impair the functionality and synchronization of a CUCM cluster.