DC-FTM Overview

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DC-ATM can be used to build fully fault-tolerant devices, where the routing and signalling state databases are replicated to back-up systems.

DC-FTM works in conjunction with DC-Signalling, DC-Call Control, and DC-PNNI to provide fault-tolerant support for ATM signalling devices that have back-up processors. Fault-tolerant support allows these systems the potential to provide 99.9999% availability.

DC-FTM in an ATM stack


Functions and Features

DC-FTM includes the following functions.

  • Maintaining all active calls and parties during hardware failures. This is achieved by replicating the signalling call and party database (CDM).

  • When transferring control to the back-up, DC-FTM supports synchronization of databases between
    • CDM and Switch Fabric Control (SFC)
    • CDM and local applications.
    This ensures that all components are synchronised regarding the status of active calls and parties. It also allows applications, SFC or the switch fabric to be on cards that are remote from the processor running DC-Signalling and DC-Call Control.

  • Integration with DC-PNNI, to provide an up-to-date routing database on the back-up to ensure that there is minimal interruption when the back-up system takes over.

  • Integration with DC-ILMI, to ensure that remote devices do not detect a change of attachment point when the back-up system takes over.

  • Support for "hot software upgrades", allowing software to be upgraded without interruption.

DC-FTM Overview

The primary side FTM is responsible for

  • synchronising the CDM databases of the primary and secondary
  • informing system management components that synchronisation has completed
  • forwarding messages between Call Control (CC) and the local switching fabric controller
  • sending replication requests (including the data to be replicated) to the secondary.

The secondary side FTM is responsible for

  • allocating resources for replication requests
  • expanding the CDM data and inserting it in the CDM when a replication is successful
  • freeing allocated resources when a replication fails.

When failover occurs, the FTM on the secondary (which is now becoming the primary) is also responsible for auditing the local switching fabric controller and initiating the audit of local ATM applications.


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