The list below includes call termination response codes sent by PortaSIP and defined in RFC 3261.

Response code

Reason message



Bad Request

The request contains malformed message syntax (e.g., absent or malformed headers, body parse error, etc.). Verify the message syntax in the UA configuration and correct it if necessary.



The request requires user authentication. The calling UA must send corresponding credentials in the new request once this response is received (during digest authentication).



The server understood the request, but refuses to fulfill it


Not Found

The called party does not exist. Check that the address specified in the Request-URI or of the server configuration is correct.


Method Not Allowed

The method specified in the Request-Line is understood, but is not allowed/supported for the address identified by the Request-URI.


Request Timeout

The called party did not answer the call so it timed out. Call again later.


Unsupported Media Type

The called party does not support any of the codecs offered. Change the set of codecs.


Temporarily Unavailable

The called party is not available (e.g., is not registered now). Try to call later.


Call Leg/Transaction Does Not Exist

This status indicates that the server received a request that does not match any existing dialog or transaction. It is sent in these cases:

  • There is a race between two sides to terminate a dialog;
  • There is a server malfunction or an incorrect request. Check the server logs.


Loop Detected

A request passed through a loop due to a misconfiguration or network configuration issues.

Another reason for the same request may be a result of forking by some earlier proxy, wherein two forked requests are passed through the same party a second time.


Too Many Hops

The server received a request that contains a Max-Forwards header field with a zero value. There is probably a loop in the network topology that must be fixed.


Busy Here

The called party is now busy on another call. Try to call later.


Request Cancelled

The call was canceled by the calling party. Call again later or check why the called party did not answer. Possible reasons could be a timeout, misconfiguration or network issue.


Not Acceptable Here

Most probably, the called party does not support any of the codecs offered. Change the set of codecs.


Bad Event

The SUBSCRIBE or PUBLISH message has an unsupported event mentioned.


Server Internal Error

The server could not fulfill the request due to some unexpected condition. The reason for this is saved in the server logs.


Not Implemented

The server is not able to fulfill the request because it does not recognize the requested method. (Compare with 405 Method Not Allowed, where the server recognizes the method but does not allow or support it.)


DNS Data Incorrect

The server is acting as a gateway or proxy, and received an invalid response from a downstream server while attempting to fulfill the request (the error message can be specified).


Service Unavailable

The server is undergoing maintenance, is temporarily overloaded, or there are no available active nodes that can handle this request. A "RetryAfter" header field may specify when the client may reattempt its request (the error message can be specified.)



The destination does not wish nor can participate in the call. Additionally, the destination knows there are no alternative destinations (such as a voicemail server) willing to accept the call (the error message can be specified).


Not Acceptable Here

The UA was contacted successfully but some aspects of the session description such as the requested media, bandwidth, or address style were not acceptable.

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