Oracle Communications Service Controller 6.2 includes an enhancement on SSU server's Sigtran High Availability. This enhancement ensures the usecase like HLR Query runs smoothly in case of a SSU server's Sigtran link is down while other Sigtran links can be selected to send out the HLR query (e.g. map ATI message) instead.
The SSU server monitors the link status(AVAILABLE/UNAVAILABLE) and report it to PN server via two means:
Immediate link Status report
Periodical current link status report
The 'Immediate link Status report' triggers when one of the link status change. The SS7 stack detects the links status change at first and then SSU instance would trigger immediate link status report propagating to PN server via event broker. Meanwhile SSU instance could trigger 'Periodical current link status report' propagating to PN server(by default 30s). the current link status report includes all link status of a SSU instance.
The PN server processes the link status report. so that be able to track each remote destination status of each ss7 protocol adapter instance in the SSU server. when PN server need to send out the HLR query outbound event. The PN server start to select an AVAILABLE ss7 protocol instance for the remote destination in the round robin way. if one of the ss7 protocol instances become UNAVAILABLE then PN server would fail over to other AVAILABLE ss7 protocol instance. The PN server marks a remote destination UNAVAILABLE only if all ss7 protocol adapter instances in all SSU servers are 'disconnected' to this destination!