IMS / SIP Messages
This category is reserved for SIP and IMS signaling used by VoNR procedures under the 5G architecture.
Use this area for INVITE, provisional responses, final responses, and session teardown references.
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IMS SIP 100 Trying
100 Trying confirms that the request was received and transaction processing has started.
IMS SIP 180 Ringing
180 Ringing shows that the terminating side is being alerted for the session request.
IMS SIP 181 Call Is Being Forwarded
181 Call Is Being Forwarded shows that the original target is redirecting or forwarding the session attempt.
IMS SIP 182 Queued
182 Queued shows that the request is waiting in a queue instead of progressing immediately.
IMS SIP 183 Session Progress
183 Session Progress shows that the session is advancing before final answer and often carries early-session SDP.
IMS SIP 200 OK
200 OK confirms that the SIP request completed successfully.
IMS SIP 202 Accepted
202 Accepted means the request was accepted for further handling, but the full outcome will be reported later.
IMS SIP 302 Moved Temporarily
302 Moved Temporarily redirects the sender to another temporary target or contact.
IMS SIP 380 Alternative Service
380 Alternative Service indicates that the original request cannot be served as asked and suggests another service path.
IMS SIP 400 Bad Request
400 Bad Request means the request could not be understood or accepted because of syntax or structural problems.
IMS SIP 401 Unauthorized
401 Unauthorized challenges the request and asks the sender to retry with authentication.
IMS SIP 403 Forbidden
403 Forbidden means the request was understood but the network or service refused to allow it.
IMS SIP 404 Not Found
404 Not Found means the target user or service could not be found at the requested destination.
IMS SIP 405 Method Not Allowed
405 Method Not Allowed means the target exists but does not allow the SIP method that was used.
IMS SIP 406 Not Acceptable
406 Not Acceptable means the request was understood, but the target cannot satisfy the acceptable formats or features indicated.
IMS SIP 407 Proxy Authentication Required
407 Proxy Authentication Required challenges the sender to authenticate through a SIP proxy, commonly the P-CSCF path.
IMS SIP 408 Request Timeout
408 Request Timeout means the expected transaction progress did not happen in time.
IMS SIP 415 Unsupported Media Type
415 Unsupported Media Type means the target cannot process the request body in the format that was sent.
IMS SIP 480 Temporarily Unavailable
480 Temporarily Unavailable means the target is currently unreachable or unavailable, but not permanently unknown.
IMS SIP 481 Call or Transaction Does Not Exist
481 Call or Transaction Does Not Exist means the receiving side could not match the request to a valid dialog or transaction.
IMS SIP 486 Busy Here
486 Busy Here means the target user is busy at the reached destination.
IMS SIP 487 Request Terminated
487 Request Terminated means the original request branch was stopped before normal completion.
IMS SIP 488 Not Acceptable Here
488 Not Acceptable Here means the request reached the target, but the local media or session offer cannot be accepted there.
IMS SIP 500 Server Internal Error
500 Server Internal Error means the server hit an internal problem while handling the request.
IMS SIP 503 Service Unavailable
503 Service Unavailable means the service cannot handle the request right now, usually for temporary server or overload reasons.
IMS SIP 504 Server Time-out
504 Server Time-out means a server did not get a timely answer from another server while handling the request.
IMS SIP 600 Busy Everywhere
600 Busy Everywhere means the request should not be retried elsewhere because the target is considered busy globally.
IMS SIP 603 Decline
603 Decline means the request was actively refused and should not be retried to other locations for the same attempt.
IMS SIP 604 Does Not Exist Anywhere
604 Does Not Exist Anywhere means the target does not exist globally for the request.
IMS SIP 606 Not Acceptable
606 Not Acceptable means no acceptable target branch can satisfy the requested session or content constraints.
IMS SIP 608 Rejected
608 Rejected means the request was rejected without exposing the more specific target-state reason.
IMS SIP ACK
ACK is the SIP request that confirms a final response to INVITE.
IMS SIP BYE
BYE is the SIP request that terminates an established dialog.
IMS SIP CANCEL
CANCEL is the SIP request that stops a pending INVITE transaction before final acceptance.
IMS SIP INFO
INFO is the SIP request used to carry mid-session information inside an existing dialog.
IMS SIP INVITE
INVITE is the SIP request that starts or modifies the main session dialog in IMS.
IMS SIP MESSAGE
MESSAGE is the SIP request used to carry standalone message content without creating a full session dialog.
IMS SIP NOTIFY
NOTIFY is the SIP request that delivers state updates for an active subscription.
IMS SIP OPTIONS
OPTIONS is the SIP request used to query capabilities or liveness without creating a full session.
IMS SIP PRACK
PRACK is the SIP request that acknowledges a reliable provisional response.
IMS SIP PUBLISH
PUBLISH is the SIP request used to publish event state toward a server that manages subscriptions.
IMS SIP REFER
REFER is the SIP request used to ask the far side to contact a third target or follow a transfer-related action.
IMS SIP REGISTER
REGISTER is the SIP request that creates, refreshes, or removes IMS service reachability for the UE.
IMS SIP SUBSCRIBE
SUBSCRIBE is the SIP request that creates or refreshes a subscription to an event package.
IMS SIP UPDATE
UPDATE is the SIP request used to modify session parameters inside an existing early or confirmed dialog.