Nice informative post e164. Have some reputation points from me
Answers in bold.
Group 1:
-Outbound SIP calls via VoXaLot (Dial plans, speed dial, ENUM/sip-code)
Correct
-Inbound SIP calls via VoXaLot
Correct
-Call forwarding to URI
Correct
Group 2: (implemented as B2BUA)
-Web Callback
Correct
-VoXCallMe
Correct
-Call forwarding to phone number via provider / dial plan
Correct
unsure:
-Provider Registrations (Inbound calls from a registered provider)
(I thought it would be "Group 1", but my tests seem to show the voice traffic transiting VoXaLot, although I'm not sure if it's because of codec negotiation or not).
For the most part these types of calls will end up as group 2. This is usually due to Codec negotiation resulting in VoXaLot transcoding or because the destination UAC is not initiating a re-invite.