I didn't realize that SIP user info is case sensitive. In any event, I have two SIP accounts with linphone, THUFIR and HAWAT. Using the Csip Android client these accounts work fine.
Also, demo_bob and demo_alice, registered on Asterisk running on the localnet, can dial each other using Csip on Android.
So far as I can tell, there's no problem with the network in terms of firewalls. Is that reasonable? I don't know how to further test that belief, however.
Is there a particular litmus test?
thanks,
Thufir