Message Throttling

Ingress Messages

GTP-C entity uses traffic reduction metric information in the Overload Control Information (OCI) for message throttling. To mitigate overload scenario, the GTP-C entity reduces the ingress message flow towards the overloaded peer based on the metric information.

When a node is in self-protection mode, the SMF rejects the ingress GTP-C messages based on the message throttling exclude configuration. For details on the exclude profile configuration, see the Create Exclude Profile section.

Egress Messages

To mitigate the GTP-C overload scenario, the SMF controls the egress message flow towards the overloaded GTP-C peer based on the information received within the OCI.

The SMF rejects the egress messages towards the GTP-C peers based on the exclude profile configuration. Exclusion profile contains the DNN list, 5QI list, ARP list, and priority corresponding to the messages to be excluded from throttling.

Peer overload control for GTP-C interface can be configured through the profile overload profile-name peer-level interface gtpc action throttle command.

Important

Message throttling applies only to the initial messages. The SMF does not throttle the triggered request or response messages as it might result in retransmission of the corresponding request message.

For throttling, the SMF uses the loss algorithm as specified in 3GPP 29.274.

Message groups are formed based on the category of procedures mentioned in 3GPP 29.274, section 12.3.9.3.2. The following are the peer overload groups for message throttling.

  • Group 1 corresponds to update of existing resources. This group includes the Update Bearer Request message.

  • Group 2 corresponds to creation of new resources. This group includes the Create Bearer Request message.

Message groups allow the user to configure, in percentage, how many number of messages SMF is expected to generate in each message group. The default value for both the groups are 50%. The default value 50% means that, out of 100 outgoing messages, 50 messages are update bearer requests (group 1) and 50 messages are create bearer requests (group 2).

If the peer is overloaded and the overload reduction matrix is 30%, then the SMF throttles 30 create bearer request messages and sends all the remaining messages.

If the peer is overloaded and the overload reduction matrix is 70%, the SMF throttles 50 create bearer request messages and 20 update bearer request messages and sends the remaining 30 update bearer messages.