Polycom SIP 3.1 - Manual (Page 289)

Session Initiation Protocol (SIP)
B - 7
3xx Responses - Redirection
4xx Responses - Request Failure
Response Supported Notes
300 Multiple Choices Yes
301 Moved Permanently Yes
302 Moved Temporarily Yes
305 Use Proxy No
380 Alternative Service No
Note All 4xx responses for which the phone does not provide specific support will be
treated the same as 400 Bad Request.
Response Supported Notes
400 Bad Request Yes
401 Unauthorized Yes
402 Payment Required No
403 Forbidden No
404 Not Found Yes
405 Method Not Allowed Yes
406 Not Acceptable No
407 Proxy Authentication Required Yes
408 Request Timeout No
410 Gone No
413 Request Entity Too Large No
414 Request-URI Too Long No
415 Unsupported Media Type Yes
416 Unsupported URI Scheme No
420 Bad Extension No
421 Extension Required No
423 Interval Too Brief No
480 Temporarily Unavailable Yes