In a voice-over-IP communications network, call data records include dynamically assigned IP signaling addresses such as IPv6 signaling addresses used in provisioning communications sessions. Those dynamically assigned IP signaling addresses are computed from customer site identification codes using a reversible algorithm. The algorithm can then be reversed to compute a customer site identification code from an IP signaling address contained in a call data record, allowing the communications network provider to perform quality monitoring and diagnostics based on call data records.