Feature Description

The SMF supports configurable back-off timer to inform the UE to wait with a re-registration and new connection attempt after a network-initiated release. This timer helps to recover the system from failure.

The SMF sends the configured back-off timer value to AMF in the following scenarios:

  • N4 path failure during a UPF switchover

  • IP address exhaustion

Important

These scenarios are currently supported only in home-routed roaming and non-roaming sessions.

The SMF sends the back-off timer value to S-GW only during the exhaustion of IP address.

Note

The back-off timer support is applicable only for the 4G non-roaming sessions and 5G roaming and non-roaming sessions.

If the SMF detects that the UPF is inactive, it includes a back-off timer and cause value in PDU Session Release Command message sent over N1. Then, SMF clears the PDU session.

When the IP addresses get exhausted while initiating the 4G attach, the PGW-C includes the back-off timer IE and cause value in Create Session Response message.

In case of IP address exhaustion during 5G attach, the SMF includes the back-off timer IE and cause value in PDU Session Establishment Reject message sent over N1.