DDN Delay Timer

  1. MME sends Release Access Bearer request to SGW-C to release downlink remote TEIDs of all the bearers for that UE.

  2. On arrival of Release Access Bearer request, SGW-C informs the same to SGW-U by updating FAR with Apply Action as BUFFER in Sx Modification Request for all the PDNs.

  3. SGW-U send Sx Modification response after applying Buffering in SGW-U for corresponding PDN.

  4. SGW-C sends Release Access Bearer response to MME.

  5. First Downlink data arriving in SGW-U triggers Sx Report Request (with Report Type as Downlink Data Report) towards SGW-C.

  6. On arrival of Sx Report Request message, the SGW-C initiates Downlink Data Notification request message towards MME.

  7. SGW-C sends Sx Report Response message towards SGW-U.

  8. Downlink Data Notification Acknowledgment is received from MME with DDN Delay Timer value. This timer value will be saved for this peer , and now onwards every Downlink Data notification that we initiate should be after this delay for that peer.

  9. On success paging, MME sends a Modify bearer request to the SGW with eNodeB TEIDs that sets up the S1-U connection at the SGW.

  10. SGW-C sends Sx Modification Request with updated FAR for new TEID information to SGW-U. SGW-U can now forward all the buffered data to UE via eNodeB.

  11. SGW-C sends Modify Bearer Response to MME.

  12. SGW-U sends Sx Modification Response to SGW-C.

  13. MME sends Release Access Bearer Request to SGW-C to release downlink remote TEIDs of all the bearers for that UE.

  14. On arrival of Release Access Bearer Request, SGW-C inform the same to SGW-U via updating FAR with Apply Action as BUFFER in Sx Modification Request for all the PDNs.

  15. SGW-U send Sx Modification Response after applying Buffering in SGW-U for corresponding PDN.

  16. SGW-C sends Release Access Bearer Response to MME.

  17. First Downlink data arriving in SGW-U triggers Sx Report Request (with Report Type as Downlink Data Report) towards SGW-C.

  18. On arrival of Sx Report Request message, SGW-C starts DDN Delay Timer. On DDN Delay timer expiry SGW-C Initiates Downlink Data Notification message towards MME.