IP Address Exhaustion Handling Call Flow for 5G Sessions
This section describes how the SMF handles the IP address exhaustion condition in 5G sessions.
Handling of IP Address Exhaustion in 5G Non-roaming Sessions
The following figure illustrates the IP address exhaustion handling call flow for 5G non-roaming sessions.

Step |
Description |
---|---|
1 |
AMF sends the SM Context Create message for the N1 PDU Session Establishment Request to SMF. |
2 |
Upon detecting the exhaustion of IP address in a 5G non-roaming call, the SMF reads the configured back-off timer and cause value. Then, SMF sends this timer and cause value in the N1 PDU Session Establishment Reject message to AMF. |
Handling of IP Address Exhaustion in 5G Roaming Sessions
The following figure illustrates the IP address exhaustion handling call flow for 5G roaming sessions.

Step |
Description |
---|---|
1 |
The AMF sends the SM Context Create message for the N1 PDU Session Establishment Request to vSMF. |
2 |
The vSMF sends Session Context Create Request message to the hSMF. |
3 |
If hSMF detects that the IP addresses are exhausted, it sends PduSessionCreateError to the vSMF with back-off timer and cause value based on configuration on hSMF. Based on this value, the vSMF includes the back-off timer and cause value in N1 PDU Session Establishment Reject message. |