SIP Response Codes

SIP Response Codes (Session Initiation Protocol)

SIP (Session Initiation Protocol) is a signaling application layer protocol designed to create, modify, and terminate a multimedia session over the Internet Protocol. It is the most common protocol used in VoIP technology. With SIP, every network element is identified by a SIP URI (Uniform Resource Identifier), which is like an address. They are broken down as 1xx Provisional Responses, 2xx Successful Responses, 3xx Redirection Responses, 4xx Client Failure Responses, 5xx Server Failure Responses and 6xx Global Failure Responses.

List of SIP Response Codes

1xx - Informational SIP Responses
  • 100 Trying – An extended search is being performed so a forking proxy must send a 100 Trying response.
  • 180 Ringing – The Destination User Agent has received the INVITE message and is alerting the user of call.
  • 181 Call Is Being Forwarded – Optional, send by Server to indicate a call is being forwarded.
  • 182 Queued – Destination was temporarily unavailable, the server has queued the call until destination is available.
  • 183 Session Progress – This response may be used to send extra information for a call which is still being set up.
  • 199 Early Dialog Terminated – Send by the User Agent Server to indicate that an early dialog has been terminated.
2xx - Success Responses
  • 200 OK – Shows that the request was successful
  • 202 Accepted – Indicates that the request has been accepted for processing, mainly used for referrals.
  • 204 No Notification – Indicates that the request was successful but no response will be received.
3xx - Redirection Responses
  • 300 Multiple Choices – The address resolved to one of several options for the client to choose.
  • 301 Moved Permanently – The original Request URI is no longer valid, the new address is given in the Contact header.
  • 302 Moved Temporarily – The client should try at the address in the Contact field.
  • 305 Use Proxy – The Contact field details a proxy that must be used to access the requested destination.
  • 380 Alternative Service – The call failed, but alternatives are detailed in the message body.
4xx - Request Failures
  • 400 Bad Request – The request could not be understood due to malformed syntax.
  • 401 Unauthorized – The request requires user authentication. Only issued by registrars. NOTE: Proxies should use proxy authorization 407.
  • 402 Payment Required – (reserved for future use).
  • 403 Forbidden
  • 404 Not Found – (User not found).
  • 405 Method Not Allowed
  • 406 Not Acceptable
  • 407 Proxy Authentication Required – The request requires user authentication.
  • 408 Request Timeout – Could not find the user in allowable time.
  • 409 Conflict
  • 410 Gone – The user existed once, but is not available here any more.
  • 411 Length Required – The server will not accept the request without a valid content length (deprecated).
  • 413 Request Entity Too Large – Request body too large.
  • 414 Request URI Too Long – The server refuses to service the request. The Req-URI is longer than the server can interpret.
  • 415 Unsupported Media Type
  • 416 Unsupported URI Scheme
  • 417 Unknown Resource-Priority – There was a resource-priority option tag, but no Resource-Priority header.
  • 420 Bad Extension – Bad SIP Protocol Extension used, not understood by the server.
  • 421 Extension Required – The server needs a specific extension not listed in the Supported header.
  • 422 Session Interval Too Small
  • 423 Interval Too Brief
  • 424 Bad Location Information
  • 433 Anonymity Disallowed – The request has been rejected because it was anonymous.
  • 480 Temporarily Unavailable – Callee currently unavailable.
  • 481 Call/Transaction Does Not Exist
  • 482 Loop Detected
  • 483 Too Many Hops
  • 484 Address Incomplete
  • 485 Ambiguous
  • 486 Busy Here – Callee is busy.
  • 487 Request Terminated – The request terminated by a bye or cancel.
  • 488 Not Acceptable Here
  • 491 Request Pending – Server has some pending request from the same dialog.
  • 493 Undecipherable – Could not decrypt MIME body part.
  • 494 Security Agreement Required – The server has received a request that requires a negotiated security mechanism.
5xx - Server Errors
  • 500 Server Internal Error – The server could not fulfill the request due to some unexpected condition.
  • 501 Not Implemented – The SIP request method is not implemented here.
  • 502 Bad Gateway
  • 503 Service Unavailable
  • 504 Server Time-out
  • 505 Version Not Supported – The SIP protocol version in the request is not supported by the server.
  • 513 Message Too Large
6xx - Global Failures
  • 600 Busy Everywhere – All possible destinations are busy.
  • 603 Decline – Destination cannot/doesn't wish to participate in the call, no alternative destinations.
  • 604 Does Not Exist Anywhere – The server has authoritative information that the requested user does not exist anywhere.
  • 606 Not Acceptable