Collision Handling of Modify Bearer Request over Modify Bearer Request Drop and Retry

Feature Summary and Revision History

Summary Data

Applicable Product(s) or Functional Area

  • P-GW

  • SAEGW

  • S-GW

Applicable Platform(s)

  • ASR 5500

  • VPC-DI

  • VPC-SI

Feature Default

Disabled - Configuration Required

Related Changes in This Release

Not Applicable

Related Documentation

  • P-GW Administration Guide

  • S-GW Administration Guide

  • SAEGW Administration Guide

  • Command Line Interface Reference

Revision History

Revision Details

Release

First Introduced.

21.28.mx

Feature Description

During a call creation MME sends the first MBR message and while S-GW processes the call, the MME can receive an E-RAB modification indication to send the second MBR to S-GW. To avoid collision over Modify bearer request (mbreq) message over mbreq, the MME supports collision of MBR over MBR Drop and Retry functionality through a mbreq-over-mbreq drop CLI configuration under the egtp-service. The following functions occur:

  • MME sends modify bearer request when service request modify bearer request is in pending state

  • S-GW drops the E-RAB procedure modify bearer request message

  • MME retries the dropped MBR until first MBR response.

Enabling or Disabling Modify Bearer Request Messages

Use the following configuration commands to configure the collision handling of Drop second MBreq when first MBreq is pending. 

configure 
   context  context_name 
      egtp-service  egtp_service_name 
         collision-handling   
             csreq-reject-cause   
             dbcmd-over-mbreq  { drop | queue } 
          mbreq-over-mbreq  { drop } 
         { default | no } collision-handling csreq-reject-cause   
         { default | no } collision-handling dbcmd-over-mbreq   
         { default | no } collision-handling mbreq-over-mbreq   
         end

NOTES:

  • csreq-reject-cause : Configures collision handling of CSreq when CSreq or DSreq is pending. The Default or No behavior rejects a new MBreq with cause - No resources available(73).

  • mbreq-over-mbreq : Configures collision handling of drop second MBreq when MBreq is pending. The Default or No behavior rejects a new MBreq with cause - No resources available(73).

  • mbreq-over-mbreq { drop } : Drops the received messages.

Monitoring and Troubleshooting

This section describes how to monitor the collision handling feature for MBR over MBR.

Show Command (s) and/or Outputs

This section provides information regarding show commands and/or their outputs in support of the collision handling on the P-GW/SAEGW/S-GW feature.

show configuration

The output of this command indicates if collision handling for the DBcmd message when the MBreq message is pending is enabled or disabled or for the mbreq over mbreq drop messages:

  • collision-handling dbcmd-over-mbreq queue

  • no collision-handling dbcmd-over-mbreq queue

  • collision-handling mbreq-over-mbreq drop

show egtp-service all-name

The output of this command indicates how the P-GW is configured to handle the MBreq when MBreq messages for the Default Bearer is pending at the P-GW or S-GW.

  • Collision handling:

    • DBcmd when MBreq pending: <Queue DBcmd>, <Drop DBcmd>, or <Abort MBreq and handle Dbcmd>

show egtpc statistics debug-info

The output of this show command has been modified to display the following fields for Collision Scenarios MBR over MBR and MBR over MBR Drop and Retry: 


 Modify Bearer Request RX:
        Total Discarded:                     1   Decode/Validation Failure:           0
        Invalid Transaction State:           0   Piggy Backing Errors:                0
        Invalid Bearer State:                1   Context Not Found:                   0
        Unknown:                             0

Error Events in EGTPC Stack :
 
Messages from invalid peer:                      0
 DBR/DSR transation created but not used:        0
 Teid Collision with uli mismatch for MBR:       0
 Teid Collision with uli mismatch for BRcmd:     0
 Teid Collision with uli mismatch for DBCmd:     0
 MBReq discarded due to pending MBReq:          1

show egtpc statistics verbose

The output of this show command has been modified to display the following fields for Collision Scenarios MBR over MBR and MBR over MBR Drop and Retry: 

Message Collision Statistics:
             
 Interface            Old Proc(Msg Type)               New Proc(Msg Type)                    Action            Counter 

SGW(S4/S11)    Non-Handover MBReq( 11)   MME/SGSN Trgr MBReq( 11)    Silent Drop New          1