Hello,
I use xocde 5.0.2 to build linphone-ios (Bundle version 2.1.2 / Bundle versions string, shore 3.5.104).
I use TCP connection, so enter background mode, it should do keep-alive (keep sip register, expire time 300 second).
I running linphone-ios on iPad device, and iphone 4s device, then sometimes I found that when App enter background mode,
it don't do keep-alive(keep register), and from SIP server monitor will see the client is logout.