How It Works

The process of auto-throttling happens through the following steps:

  1. SMF supports a new proprietary IE in PFCP association setup request coming from a UPF, which carries the maximum session capacity of a UPF.

    For more information on the support of this IE from the UPF side, see the UCC 5G UPF Configuration and Administration Guide, Release2023.03.

  2. Maximum session capacity per UPF can be configured on SMF as well. This configuration can be done per UPF configuration or per UPF, per DNN.

  3. As part of the PFCP association, the SMF allocates IP chunk to UPF per node manager.

  4. When IP usage per UPF reaches the threshold of 80% of total IP allocated, SMF tries to allocate further chunks. The allocation for a new chunk can also happen based on internal changes like pool config changes, pool threshold hit, and so on.

  5. Using this feature, SMF now compares the IP usage of the UPF, which includes current IP usage by the active sessions and also the IPs which are in quarantine, with the maximum session capacity of the UPF.

  6. SMF throttles chunk allocation, if the current usage above the maximum session capacity.