Frequently Asked Question

SIP Response Codes and their Meanings.
Last Updated 4 years ago

Session Initiation Protocol has a range of response codes as listed below. If your using GEN Hosted or Onsite Telephony and your receiving codes on your handset then please raise a ticket at the HelpDesk and we'll resolve that for you.

Informational Responses


These codes are information only and are useful in indicating the current 'state' of the call.

  • 100 Trying - Just general response to a command
  • 180 Ringing - The endpoint is ringing (apparently)
  • 181 Call Is Being Forwarded - A forward is in place
  • 182 Queued - The endpoint is queued and your in it.
  • 183 Session Progress - This just indicates that call setup is in progress and usually contains some status data in the message body.
Successful Responses

  • 200 OK - Doesn't always mean ok, but the message was accepted ok.
  • 202 accepted - It Indicates that the request has been understood but actually can’t be processed
Redirection Responses

  • 300 Multiple Choices
  • 301 Moved Permanently
  • 302 Moved Temporarily
  • 305 Use Proxy
  • 380 Alternative Service
Client Failure Responses

  • 400 Bad Request
  • 401 Unauthorized (Used only by registrars or user agents. 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
  • 408 Request Timeout (Couldn’t find the user in time)
  • 409 Conflict
  • 410 Gone (The user existed once, but is not available here any more.)
  • 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 (Bad SIP Protocol Extension used, not understood by the server)
  • 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/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 Failure Responses

  • 500 Server Internal Error
  • 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 server does not support this version of the SIP protocol
  • 513 Message Too Large
  • 580 Precondition Failure

Global Failure Responses

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

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