| Protocol | e1ap | Network | 5g |
|---|---|---|---|
| Spec | 3GPP TS 37.483 | Spec Section | Bearer Context Modification Required follow-up and related IE definitions (Release 18 baseline) |
| Direction | gNB-CU-CP -> gNB-CU-UP successfulOutcome-style follow-up | Message Type | UE-associated confirmation of CU-UP initiated bearer-change handling |
| Full message name | 5G E1AP - Bearer Context Modification Confirm |
|---|---|
| Protocol | E1AP |
| Technology | 5G |
| Direction | gNB-CU-CP -> gNB-CU-UP successfulOutcome-style follow-up |
| Interface | E1 between gNB-CU-CP and gNB-CU-UP |
| Signaling bearer / channel | UE-associated E1AP signaling / SCTP carried E1AP follow-up response on the modification-required path |
| Typical trigger | The CU-UP sent Bearer Context Modification Required and the CU-CP decided to confirm the requested bearer-control follow-up. |
| Main purpose | Confirms the control-plane follow-up chosen by the CU-CP after the CU-UP raised Bearer Context Modification Required for an existing bearer branch. |
| Main specification | 3GPP TS 37.483, Bearer Context Modification Required follow-up and related IE definitions (Release 18 baseline) |
| Release added | Release 17 |
| Procedures where used | Bearer Context Modification Required handling, CU-UP initiated bearer-change confirmation |
Bearer Context Modification Confirm is the E1AP message the gNB-CU-CP sends after Bearer Context Modification Required to confirm the control-plane action that the gNB-CU-UP requested for an active bearer context.
Confirms the control-plane follow-up chosen by the CU-CP after the CU-UP raised Bearer Context Modification Required for an existing bearer branch.
Bearer Context Modification Confirm is the CU-CP saying yes to the bearer follow-up that the CU-UP asked for.
Call flow position: The CU-UP has escalated a bearer issue and the CU-CP confirms the follow-up direction on the same procedural branch.
Typical state: The control plane accepts the need for follow-up and the bearer branch now proceeds under the confirmed decision.
Preconditions:
Next likely message: Bearer Context Modification Request or another confirmed bearer-control continuation
Call flow position: The confirm message closes the immediate decision point opened by the CU-UP initiated request.
Typical state: The bearer issue raised by the CU-UP has an accepted control-plane direction.
Preconditions:
Next likely message: A concrete bearer-control action on the confirmed path
Previous message(s): Bearer Context Modification Required
Next message(s): Bearer Context Modification Request, Later bearer-context continuation
Security context: Bearer Context Modification Confirm does not create security context. It confirms the control-plane handling of a CU-UP initiated bearer-change requirement.
BearerContextModificationConfirm ::= SEQUENCE {
protocolIEs ProtocolIE-Container { {BearerContextModificationConfirm-IEs} },
...
}
BearerContextModificationConfirm-IEs E1AP-PROTOCOL-IES ::= {
{ gNB-CU-CP UE E1AP ID, mandatory } |
{ gNB-CU-UP UE E1AP ID, mandatory } |
{ System Bearer Context Modification Confirm, mandatory },
...
}
Confirm is most meaningful when read as the control-plane answer to a CU-UP initiated bearer-change escalation.
E1AP-PDU
successfulOutcome
procedureCode: id-bearerContextModificationRequired
criticality: reject
value: BearerContextModificationConfirm
protocolIEs:
- id: id-gNB-CU-CP-UE-E1AP-ID
value: 0x00004192
- id: id-gNB-CU-UP-UE-E1AP-ID
value: 0x00000087
- id: id-System-BearerContextModificationConfirm
value:
pdu-session-list:
- pdu-session-id: 10
| IE | Required | Description |
|---|---|---|
gNB-CU-CP UE E1AP ID | Yes | Mandatory CU-CP side UE identifier used to correlate the confirm with the bearer branch under discussion. |
gNB-CU-UP UE E1AP ID | Yes | Mandatory CU-UP side UE identifier for the active bearer context that triggered the modification-required path. |
System Bearer Context Modification Confirm | Yes | Mandatory payload that confirms the control-plane follow-up for the bearer branch raised by the CU-UP. |
gNB-CU-CP UE E1AP IDMandatory CU-CP side UE identifier used to correlate the confirm with the bearer branch under discussion.
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.
gNB-CU-UP UE E1AP IDMandatory CU-UP side UE identifier for the active bearer context that triggered the modification-required path.
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.
System Bearer Context Modification ConfirmMandatory payload that confirms the control-plane follow-up for the bearer branch raised by the CU-UP.
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.
Likely cause: The confirm path may be missing, mis-correlated, or followed by a different bearer-control branch than expected.
What to inspect: Read Bearer Context Modification Confirm together with the earlier Modification Required payload.
Next step: Drive the rest of the trace from the confirmed control-plane decision, not from the original CU-UP request alone.
Modification Required is the CU-UP asking for control-plane action. Modification Confirm is the CU-CP accepting that follow-up direction.
It is the E1AP message the CU-CP sends to confirm the follow-up requested by a CU-UP initiated Bearer Context Modification Required procedure.
It matters because it shows that the CU-CP accepted the control-plane follow-up direction requested by the CU-UP.
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.