This is the round-trip network delay, in milliseconds, between the NE's local clock and a given NTP association's reference clock. This matters because high or highly variable delay reduces the achievable accuracy of NTP synchronization with that source, since NTP's algorithms assume relatively symmetric and stable network delay. For example, an NTP server reachable only over a congested or long-haul WAN link would show a much higher ntpAssociationStatusNtpAssociationDelay than a server on the local LAN, making it a less ideal time source.