How it Works
You can configure the Heartbeat capability at the interface-level, UPF profile group-level, or both. The interface-level configuration is mandatory. If the interface-level configuration is unavailable, then the Heartbeat parameters get configured with the default values. The profile-level configuration overrides the interface-level configuration.
The Heartbeat feature also extends to achieve high-availability for the Node Manager.
Interface and profile-level Heartbeat
The SMF-UPF interaction to detect the UPF path failure using the Heartbeat messages involves the following steps:
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The SMF sends a Heartbeat request message to the discovered UPF instances or profile groups based on the configured schedule.
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If the UPF instance or profile is alive, it sends a Heartbeat response to the SMF indicating that it’s operational. In case the UPF doesn’t send a Heartbeat response, then the SMF retransmits the Heartbeat request. It's based on the configured interval and the number of permitted attempts.
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After the configured count of Heartbeat message reattempts gets exhausted and the SMF doesn’t receive a response from UPF, then the SMF starts the Session release procedure for the subscribers that are associated with that UPF.
Heartbeat and High-availability in Node Manager
Each UPF instance is associated with a primary and secondary Node Manager. The secondary Node Manager acts as a standby system on which the primary manager fails over. The primary Node Manager is responsible for the IP allocation and managing the association-specific messages such as association create, update, or delete request.