cucm pub and sub and phones major connectivity issue between two sites

[baselzind]

i have cucm pub and sub 12 and a UC520-48U-T/E/F-K9 , the calls go to pstn from a sip trunk from the publisher ,

the publisher and subscriber in two different sites connected through a data link but all phones are registered on the publisher , the problem after the project went live , during work hours the publisher lose connectivity to the subscriber and the phones on the subscriber site give very breaking sound , then outside of working hours the problems disappear completely, also phones on the publisher side have no issue even during work hours , even the data link shows very low utilization during the issue , im not sure how to approach this problem and start tshooting? it feels it have to do with the

link between the two sites

[Dennis Mink]

your link between pub and sub is to have a max of 40ms round trip time. for DB sync to not be affected,  this is as per cisco recommendations.

you will need to protect the performance between sub and pub, uisng QoS, what error message do you get ? like SDL link is out of service on cucm?

let us know

[baselzind]

It just says it isn’t reachable and even the webpage won’t open , also phones quality between the two sites during working hours is very choppy, after working hours everything is back to normal and subscriber is fine and reachable, the problem there is no high utilization on the data link between the sites