SIP Status Codes

The request has been received by the next-hop server and an unspecified action is being taken to process it. The …

The UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone …

A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.

The called party is temporarily unavailable but the server has decided to queue the call rather than reject it. The …

Used to convey information about the progress of the call that is not otherwise classified. Often carries early media (ringback …

A UAS can send this to indicate that an early dialog has been terminated. Used when forking results in multiple …

The request has succeeded. For INVITE, the call has been answered. For other methods, the action has been completed successfully.

The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.

The request was successful but the server has decided not to send a NOTIFY for this SUBSCRIBE request.

The address in the request resolved to several choices, each with its own location. The user or UA can select …

The user can no longer be found at the address in the Request-URI. The client should direct future requests to …

The callee has temporarily moved to a different address. The client should retry the request at the Contact address but …

The requested resource must be accessed through the proxy given by the Contact header field.

The call was not successful but alternative services are possible. The response body contains a description of alternative services.

The request could not be understood due to malformed syntax. The client should not repeat the request without modifications.

The request requires user authentication. The response includes a WWW-Authenticate header with a challenge for the realm.

The server understood the request but is refusing to fulfill it. Authorization will not help. The request should not be …

The user specified in the Request-URI does not exist at the domain. The server has authoritative information that the user …

The method specified in the Request-Line is not allowed for the address identified by the Request-URI.

The resource identified by the request is only capable of generating responses with content characteristics not acceptable according to the …

The client must first authenticate with the proxy. The proxy returns a Proxy-Authenticate header with a challenge.

The server could not produce a response within a suitable time. The client may repeat the request without modifications at …

The requested resource is no longer available at the server and no forwarding address is known. This is expected to …

The precondition given in the request was not met. Used with SIP event state publication (RFC 3903).

The server is refusing to process the request because the message body is larger than the server is willing to …

The server is refusing to service the request because the Request-URI is longer than the server is willing to interpret.

The server is refusing the request because the message body is in a format not supported by the server for …

The server cannot process the request because the URI scheme in the Request-URI is unknown to the server.

The server did not understand the protocol extension specified in a Require or Proxy-Require header. The Unsupported header lists the …

The UAS needs a particular extension to process the request but the extension is not listed in the Supported header.

The request's Session-Expires value is too small. The Min-SE header in the response indicates the minimum acceptable session interval.

The expiration time in the request is too short. The response contains a Min-Expires header indicating the minimum allowed value.

The server requires an Identity header to verify the caller's identity but it was not included in the request.

The specific flow to a user agent has failed but other flows may succeed. Used with SIP outbound (RFC 5626).

The request has been rejected because the server policy requires caller identification and the request was anonymous.

The Identity-Info header contains a URI that the server cannot dereference to obtain the signing certificate.

The server was unable to validate the certificate referenced by the Identity-Info header. The certificate may be self-signed or from …

The server obtained the certificate from the Identity-Info header but the signature in the Identity header is invalid.

The first outbound proxy does not support the SIP outbound mechanism (RFC 5626) that the UA is trying to use.

The request cannot be fulfilled because the source has not been granted consent by the recipient. Used in consent-based communications …

The callee's end system was contacted successfully but the callee is currently unavailable. The client may retry after some time.

The UAS received a request that does not match any existing dialog or transaction. The call state may have been …

The server has detected a loop. The request was received with its own address in the Via header, indicating it …

The Max-Forwards header has reached zero, indicating the request has passed through too many proxies.

The Request-URI was incomplete. The server needs additional digits or information to route the call.

The Request-URI was ambiguous. The response body may contain a list of possible unambiguous addresses.

The callee's end system was contacted successfully but the callee is currently not willing or able to take additional calls …

The request was terminated by a BYE or CANCEL. The original request was cancelled before it could be completed.

The request was understood but the session description (SDP) is not acceptable. The response may contain a list of acceptable …

The server did not understand the event package specified in the Event header of a SUBSCRIBE request.

The request was received by a UAS that had a pending request within the same dialog. The UAS cannot process …

The request body was encrypted with S/MIME but the server cannot decrypt it. The server may lack the necessary key …

The server encountered an unexpected condition that prevented it from fulfilling the request.

The server does not support the functionality required to fulfill the request. The method is recognized but not implemented.

The server, acting as a gateway or proxy, received an invalid response from a downstream server it accessed in attempting …

The server is temporarily unable to process the request due to overloading or maintenance. The client should retry after the …

The server did not receive a timely response from an external server it accessed while attempting to process the request. …

The server does not support the SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.

The server was unable to process the request since the entire SIP message (not just the body) exceeded the size …

The server is unable or unwilling to meet some of the preconditions specified in the request for resource reservation.

The callee's end system was contacted successfully but the callee is busy and does not wish to take the call …

The callee's machine was contacted successfully but the user explicitly does not wish to or cannot participate. Unlike 600, this …

The server has authoritative information that the user indicated in the Request-URI does not exist anywhere. Unlike 404, this is …

The user's agent was contacted successfully but some aspects of the session description (SDP) are not acceptable. Unlike 488, this …

The called party did not want this call from the calling party. This response is used for robocall and spam …

An intermediary machine or process rejected the call attempt. Similar to 607 but the rejection comes from the network rather …