The OMCR accounting follows the active/active (1:1) redundancy model.
One difference in accounting behavior between the OMCR model and 1:1 redundancy model is in the processing of the accounting session-time attribute which on the protecting node denotes the time when the host was instantiated on the protecting node.
In contrast, the session-time attribute in 1:1 redundancy model is recorded almost simultaneously on both BNG nodes at the time when the host is originally instantiated.
As a result, the session-time attribute is for the most part uninterrupted during the switchover in 1:1 model whereas in OMCR model, the session-time attribute is reset on the switchover to the protecting node.