| Protocol | ims | Network | 5G and LTE |
|---|---|---|---|
| Spec | RFC 3261 / 3GPP TS 24.229 | Spec Section | SIP 486 Busy Here failure response |
| Direction | IMS network -> UE | Message Type | SIP request-failure response |
| Full message name | IMS SIP 486 Busy Here |
|---|---|
| Protocol | IMS |
| Technology | 5G and LTE |
| Common deployment | VoNR and VoLTE |
| Direction | IMS network -> UE |
| Interface | Gm with onward IMS routing |
| Signaling bearer / channel | IMS SIP signaling / Final request-failure response |
| Typical trigger | The called side is already busy and cannot accept the session. |
| Main purpose | Rejects the session attempt because the reached target is currently busy on that branch. |
| Main specification | RFC 3261 / 3GPP TS 24.229, SIP 486 Busy Here failure response |
| Release added | See specification history |
| Procedures where used | IMS Call Rejection, VoNR Busy Handling, VoLTE Busy Handling |
486 Busy Here means the target user is busy at the reached destination.
Rejects the session attempt because the reached target is currently busy on that branch.
486 means the reached destination is busy.
Previous message(s): IMS SIP INVITE
Next message(s): Procedure stop or alternate routing
Security context: Uses the same protected IMS signaling path as the INVITE branch.
SIP/2.0 486 Busy Here
Via:
From:
To:
Call-ID:
CSeq:
Content-Length: 0
This is SIP response syntax rather than ASN.1.
SIP/2.0 486 Busy Here
Via: SIP/2.0/UDP ue.example.net;branch=z9hG4bK-inv1
From: <sip:alice@example.net>;tag=mo1
To: <sip:bob@example.net>;tag=term1
Call-ID: call-001@example.net
CSeq: 1 INVITE
Content-Length: 0
| IE | Required | Description |
|---|---|---|
Status-Line | Yes | Shows the 486 failure code. |
Warning | Optional | Can add branch-specific context. |
Status-LineShows the 486 failure code.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
WarningCan add branch-specific context.
Presence: Optional
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
Likely cause: The reached destination is currently busy and cannot accept the session.
What to inspect: Check whether the busy response is branch-specific or part of wider service logic.
Next step: Compare it with any forked-branch behavior or later global responses.
It means the specific reached target is busy and cannot accept the call or session.
Decode this message with the 3GPP Decoder, inspect the related message database, or open the matching call flow to see where this signaling step fits in the full procedure.