SIP Response Codes: Status Code Description 100 Trying 180 Ringing 181 Call is being forwarded 182 Queuing 183 Session progress 200 Ok 202 Accepted 300 Multiple Choices 301 Moved permanently 302 Moved temporarily 305 Use Proxy 380 Alternative service 400 Bad request 401 Unauthorised (Register request failed) 402 Payment required 403 Forbidden 404 Not found 405 Method not allowed 406 Not acceptable 407 Proxy authentication required 408 Request timeout (e.g. ring-no-answer) 409 Conflict 410 Gone (That user is no longer here) 411 Length required 413 Request message body too long 414 Request URI too long 415 Unsupported media type 416 Unsupported URI scheme 420 Bad extension 421 Extension required 423 Interval too short 480 Temporarily not available 481 Call leg/transaction does not exist 482 Loop detected (request is looping) 483 Too many hops 484 Address incomplete 485 Ambiguous 486 Busy here 487 Request terminated (cancelled) 488 Not acceptable here 500 Internal server error 501 Not implemented (unsupported Method) 502 Bad gateway 503 Service unavailable 504 Gateway timeout 505 SIP version not supported 513 Message too large 600 Busy everywhere 603 Decline 604 Does not exist anywhere 606 Not acceptable