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:

  1. The SMF sends a Heartbeat request message to the discovered UPF instances or profile groups based on the configured schedule.

  2. 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.

  3. 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.