For each new call sent into our portal the SIP INVITE packet is mapped to a corresponding user. If you are getting no response to your INVITE this means we couldn't map to a single user, or the INVITE is ambiguous and maps to multiple users.
We primarily find the correct "User" based on:
- Username (in request URI)
- Source IP (which needs to match the Registration source IP or allowed IPs if configured separately)
- and From Header domain (when the above two match with multiple users)
Below is the example where we did not send back a Response to the INVITE.
This is because, we initially matched up to the ”Username & Source IP” and as it did match with multiple users we went back to match the “From” Header Domain however, the Realm of the customer PBX was sent only in the “To” Header Domain and not in the “From” Header Domain which meant we couldn’t recognize the User on our end.