Downlink Data Notification – Delay (DDN-D) Support

Under certain conditions, when UE triggers a service request, uplink and downlink data is triggered and is received at the SGW-C even before the Modify Bearer Request (MBR) is received causing unnecessary Downlink Packet Notification messages sent that increases the load in MME.

In such cases, the MME monitors the rate at which these events occur. If the rate becomes significant (as configured by the operator) and the MME's load exceeds an operator-configured value, the MME indicates "Delay Downlink Packet Notification Request" with parameter D to the Serving Gateway, where D is the requested delay given as an integer with multiples of 50 milliseconds, or zero. The S-GW then uses this delay in between receiving downlink data and sending the Downlink Data Notification message.

The Downlink Data Notifications are supported for both Collapsed and Pure-S calls.

Due to the distributed nature of the system, sessions from a particular MME are offloaded on different session managers. Therefore, all session managers are notified when a session is offloaded. Also, the functionality is designed to not allow all session managers to message the DEMUX manager.

  • In DDN Delay feature, DDN delay timer support is at Session Management Function.

  • When first data packet arrives, Sx/N4 Report message is initiated but DDN message is initiated from Session Management Function after the expiry of Delay timer.

  • DDN Delay feature is a peer level feature and so, it is applied for all the session on that peer from where the DDN Delay value is received.

  • In case a previous delay value was received from a peer and it is absent in the current message, the delay value will be considered as 0.

Session Recovery and ICSR is supported for DDNs.