Here is a list of SIP (Session Initiation Protocol) error codes and their descriptions:

1xx (Informational):

  • 100 Trying: The server has received the request and is attempting to process it.
  • 180 Ringing: The server has received the request and is ringing the called party.
  • 181 Call Is Being Forwarded: The server has received the request and is forwarding the call to another party.

2xx (Successful):

  • 200 OK: The request was successful and the server has accepted it.
  • 202 Accepted: The request has been accepted but has not yet been processed.

3xx (Redirection):

  • 300 Multiple Choices: The server has multiple options for the request and is sending them to the client for it to choose from.
  • 301 Moved Permanently: The requested resource has permanently moved to a new location.
  • 302 Moved Temporarily: The requested resource has temporarily moved to a new location.
  • 305 Use Proxy: The client must use a proxy to access the requested resource.

4xx (Client Error):

  • 400 Bad Request: The request was invalid or could not be understood by the server.
  • 401 Unauthorized: The client must authenticate itself to get the requested response.
  • 402 Payment Required: The server requires payment to process the request.
  • 403 Forbidden: The server refuses to fulfill the request.
  • 404 Not Found: The requested resource was not found on the server.
  • 405 Method Not Allowed: The request method is not allowed for the requested resource.
  • 406 Not Acceptable: The server cannot produce a response matching the list of acceptable values defined in the request's headers.
  • 407 Proxy Authentication Required: The client must authenticate itself to the proxy.
  • 408 Request Timeout: The server did not receive a complete request in time.
  • 413 Request Entity Too Large: The server will not accept the request because the request entity is too large.
  • 414 Request-URI Too Long: The server will not accept the request because the request-URI is too long.

5xx (Server Error):

  • 500 Internal Server Error: The server encountered an unexpected condition that prevented it from fulfilling the request.
  • 501 Not Implemented: The server does not support the functionality required to fulfill the request.
  • 502 Bad Gateway: The server received an invalid response from a downstream server while attempting to fulfill the request.
  • 503 Service Unavailable: The server is currently unable to handle the request due to a temporary overload or maintenance.
  • 504 Gateway Timeout: The server did not receive a timely response from a downstream server while attempting to fulfill the request.
  • 505 HTTP Version Not Supported: The server does not support the HTTP protocol version used in the request.


Troubleshooting SIP Errors


There are several ways to troubleshoot and resolve SIP (Session Initiation Protocol) errors. Some general steps you can take include:

  1. Check the SIP message for any syntax errors or invalid headers.
  2. Verify that the request is being sent to the correct server and URI.
  3. Check the server logs for more information about the error.
  4. If the error is related to authentication, verify that the correct credentials are being used.
  5. If the error is related to a timeout, try increasing the timeout value on the server or client.

Here are some specific steps you can take to resolve some common SIP errors:

  • 401 Unauthorized: This error occurs when the server requires authentication and the client did not provide valid credentials. To resolve this error, the client should provide valid credentials in the request.

  • 404 Not Found: This error occurs when the server cannot find the requested resource. To resolve this error, check the URI of the request to make sure it is correct and try again.

  • 408 Request Timeout: This error occurs when the server did not receive a complete request in time. To resolve this error, try increasing the timeout value on the server or client.

  • 500 Internal Server Error: This error occurs when the server encounters an unexpected condition that prevents it from fulfilling the request. To resolve this error, check the server logs for more information about the cause of the error and try again.

Keep in mind that these are just a few examples, and the steps to resolve specific SIP errors may vary depending on the specific error code and the circumstances surrounding it.