Time For Cucm and Ip Phone

[Ahmad Kefaya]

Hey all, can any one describe how the cucm take time and how ip phone that register in cucm take time ?

i know the CUCM is take time from NTP that added when install the CUCM , but how the ip phone is take time!!

Best Regards,

Ahmad Kefaya.

[Jaime Valencia · Accepted solution]

CUCM provides the time for the phone and it's determined via the date/time group associated to the DP the phone belongs to.

[Brian Meade · Accepted solution]

For SCCP phones, the phones get the UTC time from the SCCP registration messaging.  They then apply the offset based on what it receives in the config file.

For SIP phones, it usually uses the Phone NTP Reference and can fall back to checking the Date header in the SIP registration messaging.

[Ahmad Kefaya]

Hey Brian,

i want to check if i understanding correctly :-

-The CUCM is Take Time from The Ntp that i added when install it.

-the Phone is take UTC and added the Date/time Group.

But from where the phone get the UTC , from NTP server OR from CUCM.

and what is the benifits of Phone NTP Reference

Thanks alot.

[Brian Meade]

SCCP phones get the time from the SCCP messaging through a Date/Time Request/Response mechanism.  That time is from CUCM which is synced with NTP.  SCCP phones do not talk to NTP directly.

For SIP phones, they can use the Phone NTP Reference which allows the phone to directly reach out to an NTP server for their time rather than using the messaging from CUCM.  This was made since SIP doesn't have a built-in mechanism to exchange the time/date outside of looking at the Date header in SIP messaging which isn't very accurate compared to a real NTP setup.  I would suggest using a Phone NTP Reference for your SIP phones.

[Ahmad Kefaya]

thanks alot Mr.Brian