Cisco Cisco ASR 5000
PGW Restart Notification in S4-SGSN
Overview ▀
SGSN Administration Guide, StarOS Release 18 ▄
Overview
Listed below is an overview of the PRN feature in the S4-SGSN:
When the PGW Restart Notification is enabled at the S4-SGSN, the PRN bit in Node Features IE in Echo
Request message is set. This indicates to the SGW that the S4-SGSN supports PGW Restart Notification
message (PRN).
message (PRN).
The SGW sends the PRN message to the S4-SGSN in case of PGW node restart or if a path failure occurs. In
case of PGW node restart the PRN arrives without any cause, but if a path failure has occurred the PRN is
received with cause “PGW not responding”.
received with cause “PGW not responding”.
The S4-SGSN on receiving the PRN, deletes all PDN connections associated with the SGW and the restarted
PGW. It also releases the internal resources associated with those PDN connections.
The S4-SGSN prioritizes the PDN connections to be restored based on subscribed APN restoration priority (if
received from the HSS). A locally configured value as default restoration priority shall be used for a user's
PDN connection if it is not received from the HSS. Restoration priority value received in subscription record
from HSS value has more priority over locally configured default value.
PDN connection if it is not received from the HSS. Restoration priority value received in subscription record
from HSS value has more priority over locally configured default value.
If the S4-SGSN wants to restore the PDN connections, it does so by using the “reactivation requested” cause if
restoration priorty value is available irrespective of whether UE is in CONNECTED or IDLE state.
Deactivation is performed with cause “regular deactivation” if the UE is in CONNECTED state and restoration
priority is not available. If the UE is in IDLE state and restoration priority value is not available, then local
deactivation is done.
deactivation is done.