> For the complete documentation index, see [llms.txt](https://en.help.firstline.cc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://en.help.firstline.cc/feature/channels/phone/sip-code.md). # Phone SIP codes SIP responses are the codes used by Session Initiation Protocol for communication. We have put together a list of all the SIP responses known. ## Code Status | Code | Name | Description | | ---- | --------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | 100 | Trying | 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 the call. | | 181 | Call Is Being Forwarded | Optional; sent by the Server to indicate a call is being forwarded. | | 182 | Queued | Destination was temporarily unavailable; the server has queued the call until the 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 | Sent by the User Agent Server to indicate that an early dialog has been terminated. | | 200 | OK | Indicates 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 notification will be received. | | 300 | Multiple Choices | The address resolved to one of several options for the user or client to choose from. | | 301 | Moved Permanently | The original Request-URI is no longer valid; the new address is given in the Contact header.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 the address in the Contact field. | | 305 | Use Proxy | The Contact field specifies 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. | | 400 | Bad Request | The request could not be understood due to malformed syntax. | | 401 | Unauthorized | The request requires user authentication. This response is issued by UASs and registrars. | | 402 | Payment Required | (Reserved for future use). | | 403 | Forbidden | The server understood the request but is refusing to fulfill it. | | 404 | Not Found | The server has definitive information that the user does not exist at the indicated location (User not found). | | 405 | Method Not Allowed | The method specified in the Request-Line is understood but not allowed. | | 406 | Not Acceptable | The resource is only capable of generating responses with unacceptable content. | | 407 | Proxy Authentication Required | The request requires proxy authentication. | | 408 | Request Timeout | Couldn’t find the user in time. | | 409 | Conflict | User already registered (deprecated). | | 410 | Gone | The user existed once but is not available here anymore. | | 411 | Length Required | The server will not accept the request without a valid Content-Length (deprecated). | | 412 | Conditional Request Failed | The given precondition has not been met. | | 413 | Request Entity Too Large | Request body too large. | | 414 | Request-URI Too Long | Server refuses to service the request; the Request-URI is longer than the server can interpret. | | 415 | Unsupported Media Type | Request body is in an unsupported format. | | 416 | Unsupported URI Scheme | Request-URI uses a scheme unknown to the server. | | 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 | The request contains a Session-Expires header field with a duration below the minimum. | | 423 | Interval Too Brief | Expiration time of the resource is too short. | | 424 | Bad Location Information | The request’s location content was malformed or otherwise unsatisfactory. | | 428 | Use Identity Header | The server policy requires an Identity header, and one has not been provided. | | 429 | Provide Referrer Identity | The server did not receive a valid Referred-By token on the request. | | 430 | Flow Failed | A specific flow to a user agent has failed, although other flows may succeed. | | 433 | Anonymity Disallowed | The request has been rejected because it was anonymous. | | 436 | Bad Identity Info | The request has an Identity-Info header and the URI scheme contained cannot be dereferenced. | | 437 | Unsupported Certificate | The server was unable to validate a certificate for the domain that signed the request. | | 438 | Invalid Identity Header | Server obtained a certificate used to sign a request but was unable to verify the signature. | | 439 | First Hop Lacks Outbound Support | The first outbound proxy doesn’t support the “outbound” feature. | | 440 | Max-Breadth Exceeded | If a SIP proxy determined a response context had insufficient Incoming Max-Breadth to carry out a desired parallel fork, and the proxy is unwilling or unable to compensate by forking serially or sending a redirect, that proxy MUST return a 440 response. A client receiving a 440 response can infer that its request did not reach all possible destinations. | | 469 | Bad Info Package | If a SIP UA receives an INFO request associated with an Info Package that the UA has not indicated willingness to receive, the UA MUST send a 469 response containing a Recv-Info header field with Info Packages for which the UA is willing to receive INFO requests. | | 470 | Consent Needed | The source of the request did not have the recipient’s permission to make such a request. | | 480 | Temporarily Unavailable | Callee currently unavailable. | | 481 | Call/Transaction Does Not Exist | Server received a request that does not match any dialog or transaction. | | 482 | Loop Detected | Server has detected a loop. | | 483 | Too Many Hops | Max-Forwards header has reached the value '0'. | | 484 | Address Incomplete | Request-URI incomplete. | | 485 | Ambiguous | Request-URI is ambiguous. | | 486 | Busy Here | Callee is busy. | | 487 | Request Terminated | Request has been terminated by BYE or CANCEL. | | 488 | Not Acceptable Here | Some aspects of the session description of the Request-URI are not acceptable. | | 489 | Bad Event | The server did not understand an event package specified in an Event header field. | | 491 | Request Pending | Server has some pending request from the same dialog. | | 493 | Undecipherable | Request contains an encrypted MIME body which the recipient cannot decrypt. | | 494 | Security Agreement Required | The server has received a request that requires a negotiated security mechanism. | | 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 | The server received an invalid response from a downstream server while trying to fulfill a request. | | 503 | Service Unavailable | The server is in maintenance or temporarily overloaded and cannot process the request. | | 504 | Server Time-out | The server tried to access another server while processing a request and did not receive a timely response. | | 505 | Version Not Supported | The SIP protocol version in the request is not supported by the server. | | 513 | Message Too Large | The request message length is longer than the server can process. | | 555 | Push Notification Service Not Supported | The server does not support the push notification service specified in the pn-provider SIP URI parameter. | | 580 | Precondition Failure | The server is unable or unwilling to meet some constraints specified in the offer. | | 600 | Busy Everywhere | All possible destinations are busy. | | 603 | Decline | Destination cannot or does not 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 | The user's agent was contacted successfully but some aspects of the session description were not acceptable. | | 607 | Unwanted | The called party did not want this call from the calling party. Future attempts from the calling party are likely to be similarly rejected. |