In a trace of a call sporadic 401 Unauthorized SIP responses can be observed during call setup. This does not point to a problem, it is normal registration behavior.
401 Unauthorized response is the part of Registration authorization process. Due to security reasons our server requires authorization for each registration attempt.
A standard Registration authorization process is the following.
- The device starts the process of registration by sending a request Register without credentials.
- In response our system sends the message "401 Unauthorized" with an authentication header containing a nonce which is needed for the device to send a register request with encrypted credentials
- Next the device sends a new registration request with the proper encrypted credentials on which our system confirms Registration with sending 200 OK.