The Session Initiation Protocol (SIP) is widely used to control VoIP, Video Calls, and other multimedia communication over a newtork. SIP uses design elements similar to HTTP requests/responses (although they are not 1 to 1).

Following is a list of SIP Response 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 Is Being Forwarded
  • 182 Queued
  • 183 Session Progress

Successful SIP Responses – 2xx

The action was successfully received, understood, and accepted.

  • 200 OK
  • 202 Accepted (request understood, but cannot be processed)

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 (Used only by registrars or user agents. Proxies will/should use 407)
  • 402 Payment Required
  • 403 Forbidden
  • 404 Not Found
  • 405 Method Not Allowed
  • 406 Not Acceptable
  • 407 Proxy Authentication Required
  • 408 Request Timeout
  • 409 Conflict
  • 410 Gone (The user is not available here but once was)
  • 412 Conditional Request Failed
  • 413 Request Entity Too Large
  • 414 Request-URI Too Long
  • 415 Unsupported Media Type
  • 416 Unsupported URI Scheme
  • 417 Unknown Resource-Priority
  • 420 Bad Extension
  • 421 Extension Required
  • 422 Session Interval Too Small
  • 423 Interval Too Brief
  • 424 Bad Location Information
  • 428 Use Identity Header
  • 429 Provide Referrer Identity
  • 433 Anonymity Disallowed
  • 436 Bad Identity-Info
  • 437 Unsupported Certificate
  • 438 Invalid Identity Header
  • 480 Temporarily Unavailable
  • 481 Call Leg/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
  • 489 Bad Event
  • 491 Request Pending
  • 493 Undecipherable (Could not decrypt S/MIME body part)
  • 494 Security Agreement Required

Server Error SIP Responses – 5xx

The server failed to fulfill an apparently valid request.

  • 500 Server Internal Error
  • 501 Not Implemented (SIP request method is not implemented at the server)
  • 502 Bad Gateway
  • 503 Service Unavailable
  • 504 Server Time-out
  • 505 Version Not Supported (The server does not support the version of the SIP protocol used)
  • 513 Message Too Large
  • 580 Precondition Failure

Global Failure SIP Responses – 6xx

The request cannot be fulfilled at any server.

  • 600 Busy Everywhere
  • 603 Decline
  • 604 Does Not Exist Anywhere
  • 606 Not Acceptable