| Protocol | nas | Network | lte |
|---|---|---|---|
| Spec | 3GPP TS 24.301 | Spec Section | 6.4.3, 8.3.17 |
| Direction | UE to MME | Message Type | ESM signaling |
| Full message name | LTE Modify EPS Bearer Context Reject |
|---|---|
| Protocol | NAS |
| Technology | LTE |
| Direction | UE to MME |
| Interface | N1 over LTE access / S1-MME control path |
| Signaling bearer / channel | NAS signaling / Sent as the failure branch after Modify EPS Bearer Context Request. |
| Typical trigger | Triggered when the UE cannot apply the requested live bearer modification. |
| Main purpose | Returns the ESM cause that explains why the UE rejected the requested change to an active bearer. |
| Main specification | 3GPP TS 24.301, 6.4.3, 8.3.17 |
| Release added | Release 8 |
| Procedures where used | Modify EPS Bearer Context Procedure |
| Related cause values | ESM cause |
Modify EPS Bearer Context Reject is the LTE NAS message the UE sends when it cannot accept a bearer modification proposed by the network.
Returns the ESM cause that explains why the UE rejected the requested change to an active bearer.
Modify EPS Bearer Context Reject means the UE did not accept the requested change to an active bearer.
Call flow position: UE reject message sent when a requested live QoS or AMBR update cannot be accepted.
Typical state: The bearer stays active with the older definition while the requested change is rejected.
Preconditions:
Next likely message: Later bearer policy recovery handling
Call flow position: UE reject message sent when the requested TFT or packet-filter update cannot be applied.
Typical state: The bearer remains active but the requested rule change failed.
Preconditions:
Next likely message: Later bearer policy recovery handling
Previous message(s): Modify EPS Bearer Context Request
Next message(s): Bearer modification failure handling
Security context: Protected by the active NAS security context.
Modify EPS Bearer Context Reject
ESM cause
Protocol configuration options OPTIONAL
Extended protocol configuration options OPTIONAL
Read the ESM cause first and then correlate it with the bearer field the network tried to change.
Modify EPS Bearer Context Reject
Protocol discriminator: EPS session management
EPS bearer identity: 6
Procedure transaction identity: 5
Message type: Modify EPS Bearer Context Reject
ESM cause: semantic error in packet filter(s)
| IE | Required | Description |
|---|---|---|
ESM cause | Yes | Explains why the UE rejected the bearer modification. |
Protocol configuration options | Optional | May carry additional configuration-side detail related to the reject branch. |
ESM causeExplains why the UE rejected the bearer modification.
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.
Protocol configuration optionsMay carry additional configuration-side detail related to the reject branch.
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 UE may have rejected the requested bearer modification.
What to inspect: Check the returned ESM cause and the exact field the network tried to change.
Next step: Treat it as a live bearer-modification failure rather than a fresh bearer setup issue.
It is the UE message that rejects a bearer modification proposed by the network.
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.