The network architecture behind BBM, especially with the addition of video and voice, has been sort of a black box. We learned a bit about it when corporate admins had to open up the firewall for voice and video calls. Now with Android and iOS support we learn that the BBM connection works over SIP through a TLS (encryption) transport. Thanks to a new Knowledge base article we now know that it makes a SIP connection over TLS to global.uci.blackberry.com over port 443.
If you are having issues with the requests on your carrier you should check out the details here with BlackBerry. It seems like some carriers are blocking SIP to block VoIP apps.
Dan Not Registered
Posted: December 6, 2013 at 10:12 PM EST from my BlackBerry Z10 | OS 10.2.0.1803
This goes a long way to explain the sometimes poor connection performance of BBM. I had a support ticket for this but I wasn’t able to follow their instructions for submitting the log information. I hope they can solve this before too much damage has been done to the perceived reliability of BBM.