Dedicated Bearer Deactivation Call Flow

The following figure describes the Dedicated Bearer Deactivation procedure.

Dedicated Bearer Deactivation Call Flow

The dedicated bearer deactivation procedure for the EPS session is defined in 3GPP 23.401, Section 5.4.4. When the UE is attached to E-UTRAN, the dedicated bearer procedure remains the same as mentioned in the specified 3GPP section except for the following changes:

  • Any interaction towards PCRF (RAR from the PCRF/CCR-U to the PCRF) are replaced by Npcf_SMPolicyControl_UpdateNotify request from PCF to the SMF and Npcf_SMPolicyControl_Update Request from the SMF to the PCF respectively.

  • The PCC rules removed by PCF are mapped to the corresponding dedicated bearers and the bearer deactivation is triggered for these bearers.

  • All Gy and Gz interface messages are replaced by Nchf_ConvergedCharging_Update service operations.

  • The user plane resources for dedicated bearers are removed using the N4 Session Modification procedure towards UPF where PDRs, QERs and Forward Action Rule (FARs) are removed for the SDF filters for the deleted dedicated bearer.

MME-initiated Dedicated Bearer Deactivation

The MME uses the UE or MME-requested PDN Disconnection procedure to initiate the release of PDN connections. The following call flow illustrates the procedure in which the dedicated bearers are deactivated.

Note

The default bearers are not affected during the disconnection process.

MME-initiated Dedicated Bearer Deactivation

Step

Description

1

The release of Radio bearers for the UE in the ECM-CONNECTED state occurs due to local reasons such as abnormal resource limitation. The UE deletes the bearer contexts related to the released radio bearers.

2

When the eNodeB releases radio bearers, it sends an indication of bearer release to the MME. This indication could either be the Bearer Release Request (EPS Bearer Identity) message to the MME, or Initial Context Setup Complete, Handover Request Ack and UE Context Response. Path Switch Request can also indicate the release of a bearer. The eNodeB includes the ECGI and TAI in the indication sent to the MME.

3

The MME sends the Delete Bearer Command (EPS Bearer Identity, User Location Information, UE Time Zone, RAN or NAS Release Cause, if available) message per PDN connection to the S-GW to deactivate the selected dedicated bearer. RAN or NAS Release Cause indicates the RAN release cause or the NAS release cause. RAN or NAS Release Cause is only sent by the MME to the P-GW, if permitted according to the MME operator policy.

4

The S-GW sends the Delete Bearer Command (EPS Bearer Identity, User Location Information, UE Time Zone, RAN/NAS Release Cause) message per PDN connection to the P-GW.

5

If the PCC infrastructure is deployed, the P-GW informs the PCRF about the loss of resources by means of a PCEF-initiated IP‑CAN Session Modification procedure as defined in 3GPP TS 23.203 and provides the User Location Information, UE Time Zone and RAN or NAS Release cause, if available, received in the Delete Bearer Command from the S-GW if requested by the PCRF as defined in 3GPP TS 23.203. The PCRF sends an updated PCC decision to the P-GW.

Note

User Location Information and UE Time Zone may be unavailable if the MME or the S-GW are of a previous release and did not provide this information.

6

The P-GW sends a Delete Bearer Request (EPS Bearer Identity) message to the S-GW.

7

The S-GW sends the Delete Bearer Request (EPS Bearer Identity) message to the MME.

8

This step involves invoking Step 5 through Step 8. Note that these steps are omitted if the bearer deactivation was triggered by the eNodeB in Step 1 and Step 2.

Also, these steps are omitted if the MME initiated bearer release due to failed bearer set up during handover, the UE and the MME deactivate the failed contexts locally without peer-to peer ESM signaling.

9

The MME deletes the bearer contexts related to the deactivated EPS bearer and acknowledges the bearer deactivation to the S-GW by sending a Delete Bearer Response (EPS Bearer Identity, User Location Information (ECGI)) message.

10

The S-GW deletes the bearer context related to the deactivated EPS bearer and acknowledges the bearer deactivation to the P-GW by sending a Delete Bearer Response (EPS Bearer Identity) message.

SMF-initiated Dedicated Bearer Deactivation

The following procedure describes the SMF-initiated dedicated bearer deactivation process as defined in 3GPP TS 23.203.

Note

Default bearers are not affected during the dedicated bearer deactivation process.

  • The SMF-initiated delete bearer is triggered using the clear subscriber command.

  • If the PCC infrastructure is deployed, the P-GW informs the PCRF about the loss of resources by means of a PCEF-initiated IP‑CAN Session Modification procedure and provides the User Location Information, UE Time Zone and RAN or NAS Release cause, if available, received in the clear subscriber command if requested by the PCRF. The PCRF sends an updated PCC decision to the P-GW.

  • The P-GW sends a Delete Bearer Request (EPS Bearer Identity) message to the S-GW.

  • The S-GW deletes the bearer context related to the deactivated EPS bearer and acknowledges the bearer deactivation to the P-GW by sending a Delete Bearer Response (EPS Bearer Identity) message.

The following call flow illustrates the SMF-initiated dedicated bearer deactivation.

SMF-initiated Dedicated Bearer Deactivation