| Protocol | nas | Network | lte |
|---|---|---|---|
| Spec | 3GPP TS 24.301 | Spec Section | 6.5.2, 8.3.22 |
| Direction | UE to MME | Message Type | ESM signaling |
| Full message name | LTE PDN Disconnect Request |
|---|---|
| Protocol | NAS |
| Technology | LTE |
| Direction | UE to MME |
| Interface | N1 over LTE access / S1-MME control path |
| Signaling bearer / channel | NAS signaling / Sent after the UE is registered and one PDN connection is already active. |
| Typical trigger | Triggered when the UE wants to release an active PDN connection such as IMS or another APN. |
| Main purpose | Requests removal of an active PDN connection so the network can start the corresponding bearer release handling. |
| Main specification | 3GPP TS 24.301, 6.5.2, 8.3.22 |
| Release added | Release 8 |
| Procedures where used | UE Requested PDN Disconnect Procedure |
| Related timers | T3492 |
PDN Disconnect Request is the LTE NAS session-management message the UE sends when it wants to release one PDN connection and its associated default bearer.
Requests removal of an active PDN connection so the network can start the corresponding bearer release handling.
PDN Disconnect Request is the LTE NAS message the UE uses to release one PDN connection while staying registered.
Call flow position: UE-originated session-management message sent when the UE no longer wants a PDN connection.
Typical state: The UE is registered and is releasing one active PDN connection, not leaving EPS entirely.
Preconditions:
Next likely message: Deactivate EPS Bearer Context Request or PDN Disconnect Reject
Call flow position: UE-originated release message used when an additional PDN such as IMS should be removed.
Typical state: Other EPS registration state may remain active even though one PDN connection is being removed.
Preconditions:
Next likely message: Deactivate EPS Bearer Context Request or PDN Disconnect Reject
Previous message(s): Activate Default EPS Bearer Context Accept, Activate Dedicated EPS Bearer Context Accept
Next message(s): Deactivate EPS Bearer Context Request, PDN Disconnect Reject
Security context: Protected by the active NAS security context because it affects active PDN and bearer state.
PDN Disconnect Request
Linked EPS bearer identity
Protocol configuration options OPTIONAL
Extended protocol configuration options OPTIONAL
Read this message from the linked EPS bearer identity first because that tells you which PDN connection is being released.
PDN Disconnect Request
Protocol discriminator: EPS session management
EPS bearer identity: 0
Procedure transaction identity: 7
Message type: PDN Disconnect Request
Linked EPS bearer identity: 5
| IE | Required | Description |
|---|---|---|
Linked EPS bearer identity | Yes | Identifies the default bearer and PDN connection the UE wants to disconnect. |
Protocol configuration options | Optional | May carry additional protocol-side information related to the disconnect request. |
Linked EPS bearer identityIdentifies the default bearer and PDN connection the UE wants to disconnect.
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 protocol-side information related to the disconnect request.
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 sent PDN Disconnect Request for that APN or PDN connection.
What to inspect: Check the linked EPS bearer identity and the later deactivation or reject branch.
Next step: Treat the trace as PDN release, not a full EPS detach.
It is the UE message that asks the network to release one active PDN connection.
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.