SIP Client Error ResponsesAdded by IBM on November 30, 2011 | Version 1 (Original)
|The 4xx responses are definite failure responses from a particular server.
The 4xx responses are definite failure responses from a particular server.
Table 1. Client Error Responses (excerpt)
Parent topic: SIP Overview
|400||Bad request||The request could not be understood due to malformed syntax. The Reason-Phrase should identify the syntax problem in more detail, for example, “Missing Call ID header field”.|
|401||Unauthorized||The request requires user authentication. This response is issued by User Agent Servers and registrars, while 407 (Proxy Authentication Required) is used by proxy servers.|
|402||Payment Required||Reserved for future use.|
|403||Forbidden||The server understood the request, but is refusing to fulfill it. Authorization will not help, and the request should not be repeated.|
|404||Not Found||The server has definitive information that the user does not exist at the domain specified in the Request-URI. This status is also returned if the domain in the Request-URI does not match any of the domains handled by the recipient of the request. |
|482||Loop Detected||The server has detected a loop|
|484||Address Incomplete||The server received a request with a Request-URI that was incomplete. Additional information should be provided in the reason phrase. This status code allows overlapped dialing. With overlapped dialing, the client does not know the length of the dialing string. It sends strings of increasing lengths, prompting the user for more input, until it no longer receives a 484 (Address Incomplete) status response.|
|486||Busy Here||The called party's end system was contacted successfully, but the called party is currently not willing or able to take additional calls at this end system. The response may indicate a better time to call in the Retry-After header field. The user could also be available elsewhere, such as through a voice mail service. Status 600 (Busy Everywhere) should be used if the client knows that no other end system will be able to accept this call.|