The call flow in Figure: EFH call flow - user disconnects during EFH shows a scenario where EFH is activated before the session is established with the OCS. The scenario is similar when EFH is activated by a CCR-U message.
The initial Diameter Gy session setup fails: the CCR-I message sent to the primary peer times out or an error condition occurs that triggers Diameter Gy EFH. If failover is enabled, the CCR-I message is resent on the secondary peer. The CCR-I message sent to the secondary peer times out or an error condition occurs that triggers Diameter Gy EFH.
EFH becomes active for this user session. Interim credit is assigned to all rating groups and, optionally, a validity time is installed.
Interim credit is exhausted for a rating group or a validity time expires. A new attempt is made to establish the Diameter Gy session with the OCS; a CCR-I message is sent to the primary peer. A timeout or an error condition occurs that triggers Diameter Gy EFH to become active. If failover is enabled, the CCR-I message is resent on the secondary peer. The CCR-I message sent to the secondary peer times out or an error condition occurs that triggers EFH.
Interim credit is assigned to all rating groups and, optionally, a validity time is installed.
The user disconnects, resulting in a termination of the user session.
If interim credit reporting is enabled, a CCR-T is sent reporting the accumulated consumed interim credit.
If the OCS becomes reachable, a CCA-T may be received. Because the Diameter Gy session was not established with the OCS, the result code is DIAMETER_UNKNOWN_SESSION_ID.