Summary Data

Revision History

During NB-IoT/Control Plane CIoT EPS Optimization, user data gets transported or SMS messages are passed through MME. This is done by encapsulating them in Non-Access Stratum (NAS), reducing the total number of Control Plane messages when handling a short data transaction. If the Control Plane CIoT EPS Optimization applies, then the MME.

• Indicates S11 interface User Plane (S11-U) tunneling of the NAS user data and sends its own S11-U IP address and MME DL Tunnel End Point Identifier (TEID) for Downlink (DL) data forwarding to the S-GW.

• The S-GW returns a Create Session Response, for Control Plane CIoT EPS optimization, with the S-GW address for S11-U and S-GW TEID. They are used by the MME to forward the Uplink (UL) data toward the S-GW.

In such instances, there might be following constraints:

• S-GW validates Modify Bearer requests (MBR) without S11-U F-TEID.

• If there is no S11-U F-TEID in the MBR, then the S-GW rejects the Inter-MME Handover (HO), since F-TEID is considered mandatory when S11TF flag is set.

To overcome the above constraints and to address the requirements of the IoT devices, the S-GW supports Inter-MME Handover Modify Bearer Requests, without the S11-U TEID functionality, for the NB-IoT subscribers.

When the feature is enabled under S-GW Service Configuration mode, the following validation takes place:

• Handling of IE validation at EGTP Protocol

• Downlink data handling

• Uplink data handling

Call Flow

Handling IE Validation at EGTP Protocol: When Handling IE validation at EGTP Protocol is enabled using the mme-s11u-without-teid CLI command under S-GW Service Configuration mode, and the flag is set to be TRUE (default is FALSE):

• The S11-U TEID validation is bypassed.

• The S-GW accepts the Modify Bearer Request and continues the process until handover is successful.

The following table explains the function between MME and S-GW during initial attach procedure.

Downlink Data Handling: S-GW receives the Downlink data from P-GW. If MME S11-U TEID is not available in the S-GW bearer context or if the S11-U interface is inactive, the S-GW buffers the DL packets and initiates Downlink Data Notification to MME with the following steps.

Uplink Data Handling: S-GW accepts the Uplink data received from the MME and forwards the data to P-GW on S5/S8 interface. For example, the following steps occur at the time of handling Uplink data when Modify Bearer Request is received without the MME S11-U TEID.

Use the following configuration to enable/disable the Inter-MME Handover for Modify Bearer Requests without S11-U TEID feature.

configure 
    context context_name 
      sgw-service service_name 
        [ no | default ] egtp modify-bearer-req accept mme-s11u-without-teid  
          end 

NOTES:

• default : Disables the feature. The feature is disabled by default.

• egtp modify-bearer-req accept mme-s11u-without-teid : Enables the S-GW to accept MBR without S11u TEID IE present in the Request Message.

• no: Disables the feature.

Verifying Inter-MME Handover for Modify Bearer Requests without S11-U TEID Feature Configuration

Use the show sgw-services name sgw_service or the show configuration CLI command to verify if the feature is Enabled or Disabled.

This section provides information regarding commands available to monitor and troubleshoot the Inter-MME Handover for Modify Bearer Requests without S11-U TEID on the P-GW/S-GW.