SIP responses, class 4: Request failures

• 400 Bad Request
• 401 Unauthorized: Used only by registrars. Proxys should use proxy authorization 407
• 402 Payment Required (Reserved for future use)
• 403 Forbidden
• 404 Not Found: User not found
• 405 Method Not Allowed
• 406 Not Acceptable
• 407 Proxy Authentication Required
• 408 Request Timeout: Couldn't find the user in time
• 409 Conflict
• 410 Gone: The user existed once, but is not available here any more.
• 413 Request Entity Too Large
• 414 Request-URI Too Long
• 415 Unsupported Media Type
• 416 Unsupported URI Scheme
• 420 Bad Extension: Bad SIP Protocol Extension used, not understood by the server
• 421 Extension Required
• 422 Session Interval Too Small
• 423 Interval Too Brief
• 480 Temporarily Unavailable
• 481 Call/Transaction Does Not Exist
• 482 Loop Detected
• 483 Too Many Hops
• 484 Address Incomplete
• 485 Ambiguous
• 486 Busy Here
• 487 Request Terminated
• 488 Not Acceptable Here
• 491 Request Pending
• 493 Undecipherable: Could not decrypt S/MIME body part

• SIP | SIP Response Codes | 1xx | 2xx | 3xx | 4xx | 5xx | 6xx