Check SIP authentication (SIP Invite) for outgoing calls
In this article, we assume that you have access to the SIP traces of the telephone system. Alternatively, we will show you how to "Create network recordings with Wireshark".
Please note that this topic requires advanced knowledge of VoIP and network technology. If in doubt, please contact your network technician.
Technical Background
When an IP call is established, one party sends a “SIP Invite” to invite another participant to the call. In addition to the “technical parameters,” this message also contains information about the calling party. A separate SIP Invite is also generated for call forwarding.
To ensure that our infrastructure can uniquely identify this and reliably route the call, it is crucial that the SIP username associated with the calling phone number be transmitted in the “SIP from address User Part” field—or “From-User-Part” for short. If this is not done, our infrastructure will reject the outgoing call attempt for security reasons.
Possible Causes of Errors
In everyday use, we regularly observe that systems are configured so that, in the From-User-Part, the User Provided Number (UPN)—that is, the phone number to be displayed to the other party—is transmitted instead of the SIP username.
Please use one of the following fields for the UPN:
P-Asserted-Identity
,P-Preferred-Identity
, orFrom-Display
Remote Party ID
For more information, see our article “Configuring CLIP No Screening Correctly.”
That's right
Here is an extract from a trace showing a correctly configured SIP Invite. The key details of the call are as follows:
Number range: 07727-12345 (000-999)
SIP username: 0043772712345
UPN: In the From-Display field (here, 0772712345)
Registrar: sip.easybell.com
From: "03080951055" <sip:0043772712345@sip.easybell.com>;tag=xxxyyyzzz SIP Display info: "0772712345" SIP from address: sip:0043772712345@sip.easybell.com SIP from address User Part: 0043772712345 SIP from address Host Part: sip.easybell.com SIP from tag: xxxyyyzzz
If the data in your connection traces is transmitted as shown in this example, you can rule out the caller ID configuration as the cause.
If not, please check the PBX settings for outgoing calls and, in particular, for call forwarding. You’ll find instructions for numerous models in our Help section. If in doubt, please contact the PBX manufacturer for assistance with setup.