19B URCMP based restart procedures

23.0073GPPRelease 18Restoration proceduresTS

Across URCMP based interfaces, an MME and UCMF Node shall utilize URCMP Heartbeat Request and Heartbeat Response messages to detect and handle a peer URCMP entity failure or restart. A URCMP entity shall be prepared to receive a Heartbeat Request message at any time (even from unknown peers), and it shall reply with a Heartbeat Response message.

A URCMP entity shall maintain two Recovery Time Stamps:

– in volatile memory a remote Recovery Time Stamp of a peer URCMP entity with which the entity is in contact;

– in non-volatile memory own, or local Recovery Time Stamp that was sent to a peer URCMP entity.

After a URCMP entity has restarted and if it loses all dictionary mapping information between UE Radio Capability Information and UE Radio Capability IDs, it shall immediately update all local Recovery Time Stamps and shall clear all remote Recovery Time Stamps.

A URCMP entity may have a common local Recovery Time Stamp for all peer URCMP entities, or it may have a separate local Recovery Time Stamp for each peer URCMP entity.

A URCMP entity may probe the liveliness of each peer URCMP entity with which it is in contact by sending a Heartbeat Request message (see clause 20 "Path management procedures").

The Recovery Time Stamp signalled in the URCMP Heartbeat Request and Response messages is associated with the URCMP entity identified by the source IP address of the message.

The URCMP entity that receives a Recovery Time Stamp Information Element from a peer URCMP entity shall compare the received remote Recovery Time Stamp value with the previous Recovery Time Stamp value stored for that peer URCMP entity.

– If no previous value was stored, the Recovery Time Stamp value received in the Heartbeat Request or Response messages shall be stored for the peer URCMP entity.

– If the value of a Recovery Time Stamp previously stored for a peer URCMP entity is smaller than the Recovery Time Stamp value received in the Heartbeat Request or Response messages, this indicates that the entity that sent the Heartbeat Request or Response messages has restarted. The received, new Recovery Time Stamp value shall be stored by the receiving entity, replacing the value previously stored for the peer URCMP entity.

– If the value of a Recovery Time Stamp previously stored for a peer URCMP entity is larger than the Recovery Time Stamp value received in the Heartbeat Request or Response message, this indicates a possible race condition (newer message arriving before the older one). The received Sx node related message and the received new Recovery Time Stamp value shall be discarded and an error may be logged.