[Freeswitch-users] keep-alive RE-INVITE dropped calls

hi, im suffering call drops from carrier in roughly 15mins and i reported this to the carrier and they replied with the below: If the duration of the call was a multiple of 15 minutes, please make sure that you can properly respond to the keep-alive RE-INVITE that we sends every 15 minutes. i have no clue on how this works in FS so can any1 point me the right direction on how to sole this, we use FS to route calls from our switch to carrier -- Regards, Bipin