The following common SIP error codes are available to assist you in troubleshooting with SIP.US Support:
401 Unauthorized - An expected response for a REGISTER packet, in which the phone system should follow up with a second REGISTER packet containing the AUTH header. Sometimes inbound calls from user systems respond to SIP.US call INVITES with a 401, but SIP.US voice service does not support inbound call authentication so our Support teams treat this as an error.
403 Forbidden - This indicates incorrect SIP credentials (wrong password), an IP ban, or in the case of your SIP.US billing plan, a negative account balance.
404 Not Found - For inbound calls, it means the inbound routing to the phone system is not properly configured and the DID is not reachable by any logic of the device. For outbound, a 404 can mean the number is not programmed, it is unreachable, or is not an in-service number.
486 Busy Here - The receiving party/extension is busy or unable to accept the call due to a user/device setting.
487 Request Terminated - Someone/Something hung up the call. This can occur for outbound calling if an outbound route fails to connect to send a call INVITE or if the originating (calling) party terminates the call attempt.
500 Server Internal Error - Something is wrong with the server that is giving this code. This can occur on outbound calls if the route fails to process the request (for various possible reasons). Some PBXs can return this error when attempting to process an inbound call.
503 Service Unavailable - Something is wrong with the server that is giving this code. The server is unable to complete the outbound call request to connect.
603 Decline - The receiving party has declined the call Invite. This is commonly associated with a caller ID block, but can also result from Do Not Disturb settings enabled by the receiving user.
100 TRYING – For inbound, the phone system is processing the inbound call delivered from SIP.US. For outbound, SIP.US is attempting to reach the destination point.
180 RINGING – For inbound and outbound, the phone system is ringing the endpoint (user).
200 OK – For inbound, the phone system has accepted and established the call and sends confirmation. For outbound, the far end has accepted the established the call.
ACK – For inbound, the 200 OK reaches SIP.US from the phone system and SIP.US understands the call is now active and acknowledges. For outbound, the 200 OK from the far end reaches SIP.US and the acknowledgement is sent back to the far end.
486 BUSY – For inbound, the phone system reports that the endpoint (user) has received and rejected the call invite. This could be due to manual rejection, Do Not Disturb, or improperly configured user settings. For outbound, the far end rejects the call. This could be a manual rejection, a carrier rejection (spam suspected), the receiving party has blocked the caller ID, or the receiving party is on another call and the line is busy.