Client error
Client error responses indicate that a request message was received by a server that contains syntax that the server cannot understand (i.e. contains a syntax error) or cannot comply with. Client error responses include the following reason codes and reason phrases:
400 Bad request 401 Unauthorized
402 Payment required 403 Forbidden
404 Not found 405 Method not allowed
406 Not acceptable 407 Proxy authentication required
408 Request time-out 409 Conflict
410 Gone 411 Length required
413 Request entity too large 414 Request-URL too large
415 Unsupported media type 420 Bad extension
480 Temporarily not available
481 Call leg/transaction does not exist
482 Loop detected 483 Too many hops
484 Address incomplete 485 Ambiguous
486 Busy here 487 Request canceled
488 Not acceptable here