System Maintenance

This module includes the following types of activities related to Xenon.

• On-line installation of new hardware and software.
• System startup
• Failure detection and recovery.
• Preventive maintenance including audits intended to isolate problems before they become critical.
• Performance monitoring and statistics collection
• Synchronization with other control systems like the Access Network and the Exchange Network for Xenon.

The importance of these activities and hence of this module lies in the fact that they support the mainline call processing functional activities.

This module has entities existing on CAS as well as XEN card. The following is a list of entities constituting this module along with a brief description. 

Central Configuration Manager

This task deals with functions of System Initialization, Interface to various XEN cards, Software and Database download and active-standby management. It resides on the CAS card. It also participates in the failure detection, fault recovery, preventive maintenance and performance monitoring.

XEN Fault Handling

XEN cards are configured in an n+x redundancy configuration. Where one standby card can switch in on failure of any other XEN card in the same chassis. (For details, refer to the section on hardware design)

The following steps explain how XEN failure and status change are handled by the Central Configuration Manager.

1. When a XEN card fails, other XEN card in the same chassis will detect the failure.
2. All XENs communicating with the failed XEN may also report protocol faults.
3. A fault trigger will be sent to the Central Configuration Manager (CCM).
4. When CCM receives the trigger it changes the status of the failed card to SUSPECT.
5. CCM also asks XEN cards to clear all calls associated with the failed XEN.
6. A redundant XEN card switches in for the failed card and re-establishes protocol with all the XEN cards.
7. Hardware diagnostics are then triggered on the SUSPECT card.
8. If the card passed hardware dignostics, it is brought back into service. If the diagnostics fail, the XEN card is marked as FAILED and the operator is requested to replace the card.
9. When the operator replaces the card, CCM reruns diagnostics on the replacement card.
10. If the card passes diagnostics, it is brought back into service. The status of the XEN card is changed to INSERVICE.

CAS Fault Handling

CCM also handles the CAS card fault handling. Both the CAS cards exchange watchdog signals and health messages. If one card fails to send health messages the other CAS card takes over.

XEN Configuration Manager

The XEN Configuration Manager (XCM) works as an agent for CCM. It handles interactions with CCM and responds to CCM commands to run hardware diagnostics. XCM also handles CCM requests to clear calls to a specified XEN.

This task also monitors the health of other XEN cards in the same chassis by exchanging health check messages.

XCM also reports digital trunk faults to the V5.2 and SS7 subsystems. The actual fault handling of the digital trunk depends on the protocol. For example, failure of a digital trunk belonging to a V5.2 interface would typically lead to clearing of calls handled by that digital trunk. The affected interface would work with reduced capacity till the trunk is restored. In a similar fashion, failure of an SS7 digital trunk will result in call clears and capacity reduction.

Fault Triggers

The XEN Configuration Manager handles the following triggers:

• Health monitoring failure
• Watchdog timeout
• Digital trunk failure
• Protocol Faults