SIP Status Codes

This is a list of the known SIP status codes

Information SIP Responses – 1xx

Informational responses, indicate that the server contacted is performing some further action and does not yet have a definitive response. A server sends a 1xx response if it expects to take more than 200 ms to obtain a final response.

100 - Trying
180 - Ringing
181 - Call Being Forwarded
182 - Call Queued
183 - Session Progress

Successful SIP Responses – 2xx

The action was successfully received, understood, and accepted.

200 - OK
202 - Accepted

Redirection SIP Responses – 3xx

Further action needs to be taken in order to complete the request.

300 - Multiple Choices
301 - Moved Permanently
302 - Moved Temporarily
305 - Use Proxy
380 - Alternative Service

Client Error SIP Responses – 4xx

The request contains bad syntax or cannot be fulfilled at the server.

400 - Bad Request
401 - Unauthorized
402 - Payment Required
403 - Forbidden
404 - Not Found
405 - Method Not Allowed
406 - Not Acceptable
407 - Proxy Authentication Required

This code is similar to 401 (Unauthorized), but indicates that the client MUST first authenticate itself with the proxy. SIP access authentication is explained in Sections 26 and 22.3.

This status code can be used for applications where access to the communication channel (for example, a telephony gateway) rather than the callee requires authentication.

408 - Request Timeout

The server could not produce a response within a suitable amount of time, for example, if it could not determine the location of the user in time. The client MAY repeat the request without modifications at any later time.

409 - Conflict
410 - Gone
411 - Length Required
413 - Request Entity Too Large
414 - Request URI Too Long
415 - Unsupported Media Type
416 - Unsupported URI Scheme
420 - Bad Extension
421 - Extension Required
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

Server Error SIP Responses – 5xx

The server failed to fulfill an apparently valid request.

500 - Server Internal Error
501 - Not Implemented
502 - Bad Gateway
503 - Service Unavailable

The server is temporarily unable to process the request due to a temporary overloading or maintenance of the server. The server MAY indicate when the client should retry the request in a Retry-After header field. If no Retry-After is given, the client MUST act as if it had received a 500 (Server Internal Error) response.

A client (proxy or UAC) receiving a 503 (Service Unavailable) SHOULD attempt to forward the request to an alternate server. It SHOULD NOT forward any other requests to that server for the duration specified in the Retry-After header field, if present.


504 - Server Time-Out
505 - Version Not Supported
513 - Message Too Large

Global Failure SIP Responses – 6xx

The request cannot be fulfilled at any server.

600 - Busy Everywhere
603 - Declined
604 - Does Not Exist Anywhere
605 - Not Acceptable