RFVoLTE SIP Requests and Response Codes: A Detailed Guide
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This article outlines the various SIP requests and response codes used in Voice over LTE (VoLTE) communication. Understanding these elements is key to troubleshooting and comprehending the signaling process within VoLTE networks.
VoLTE SIP Requests
The following table details the common SIP requests used in VoLTE. These requests facilitate call setup, maintenance, and termination.
| VoLTE SIP Request | Description |
|---|---|
| INVITE | The client is invited to participate in a call session. This is the initial request to establish a call. |
| ACK | Confirms the reception of the final response by the client for an INVITE request. It acknowledges that the INVITE was successfully processed (or that an error response was received and understood). |
| BYE | Indicates the termination of a call. This message is sent by either the caller or the called party when one of them wishes to end the session. |
| CANCEL | Indicates the cancellation of any pending request. This is often used to stop a ringing phone before the call is answered. |
| OPTIONS | This message queries the capabilities of servers. It allows a client to discover what features and functionalities a server supports. |
| PRACK | Indicates provisional acknowledgement. Used to reliably acknowledge provisional responses (1XX responses) in a SIP dialog. |
| SUBSCRIBE | Indicates a subscription to event notification. A client can subscribe to receive notifications about certain events occurring on the server (e.g., presence status). |
| NOTIFY | This message notifies a subscriber if there are any new events. It’s the response to a SUBSCRIBE request, delivering the requested event information. |
| PUBLISH | This message publishes an event to the server. Used for updating the server about a certain event or status. |
| INFO | Carries mid-session information which does not modify the session state. This can be used to convey supplementary information during a call. |
| REFER | Asks the recipient to issue a SIP request (i.e., call transfer). This request initiates a call transfer process. |
| MESSAGE | Transports instant messages using SIP. This allows for sending text messages within the SIP framework. |
| UPDATE | Modifies the state of a session without changing the state of the dialog. This can be used to update session parameters during a call. |
VoLTE SIP Codes
The following table provides a description of common SIP response codes used in VoLTE. These codes indicate the status of a SIP request and provide valuable information for debugging network issues.
| VoLTE SIP Code | Description |
|---|---|
| 1XX | Provisional Responses |
| 100 | Trying |
| 180 | Ringing |
| 181 | Call is being forwarded |
| 181 | Queued |
| 183 | Session progress |
| 199 | Early dialog terminated |
| 2XX | Successful response |
| 200 | OK |
| 202 | Accepted |
| 204 | No notification |
| 3XX | Redirection response |
| 300 | Multiple choices |
| 301 | Moved permanently |
| 302 | Moved temporarily |
| 305 | Use proxy |
| 380 | Alternative service |
| 4XX | Client Failure Response |
| 400 | Bad Request |
| 401 | Unauthorized |
| 402 | Payment required |
| 403 | Forbidden |
| 404 | Not found |
| 405 | Method not allowed |
| 406 | Not acceptable |
| 407 | Proxy Authentication Required |
| 408 | Request Timeout |
| 410 | Gone |
| 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 |
| 428 | Use identity Header |
| 429 | Provide Referer Identity |
| 430 | Flow Failed |
| 433 | Anonymity Disallowed |
| 436 | Bad Identity Info |
| 437 | Unsupported Certificate |
| 438 | Invalid Identity Header |
| 439 | First Hop Lacks Outbound Support |
| 440 | Max Breadth Exceeded |
| 469 | Bad Info Package |
| 470 | Consent Needed |
| 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 |
| 494 | Security Agreement Required |
| 5XX | Server Failure Response |
| 500 | Server Internal Error |
| 501 | Not implemented |
| 502 | Bad Gateway |
| 503 | Service Unavailable |
| 504 | Server Time Out |
| 505 | Version Not Supported |
| 513 | Message too large |
| 580 | Precondition Failure |
| 6XX | Global Failure Response |
| 600 | Busy Everywhere |
| 603 | Decline |
| 604 | Does not exist anywhere |
| 606 | Not acceptable |
