[ntp:questions] Motorola Canopy CMM as NTP server

Dmitry Ivanov dimss at telecentrs.lv
Fri Sep 29 09:35:38 UTC 2006


Motorola Canopy is wireless networking system. Up to six Canopy 
sector access points (AP) can be used together as cluster 
managed by CMM (Cluster Management Module). CMM contains GPS 
receiver which is used to synchronize multiple transmitters. CMM 
has IP address and NTP server running on port 123. The server 
reports itself as Stratum-1.

Some people use CMM as primary time source of their networks. I 
have tried this too. But my ntpd quickly "disqualified" 
those "Stratum-1" units and reverted to Stratum-2 servers! ntpq 
showed that CMM units had unacceptable jitter values (hundreds 
of milliseconds).

Packet sniffer showed that Canopy CMM always reports time  
rounded to integer number of seconds. This is the problem. CMM 
has very accurate GPS time inside it but reports only seconds 
through NTP. I am unsure is it bug or "feature".

I have requested feedback from Motorola. For now, do not use 
Canopy CMM as NTP server for anything but Canopy equipment.


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