Arbitration

The Arbitration Service is installed on any computer that has a AVEVA Enterprise SCADA service that is arbitrated. Other Arbitrated services that are installed, for example: RealTime, are defined as dependent on the Arbitration Service.

The Arbitration Service is responsible for adding and removing the floating IP address for each service that is Hot on the given computer. As the underlying services become Hot, the associated IP address for the service is added to the configured Network Interface Controller (NIC). As the underlying services move away from Hot, the associated IP address for the service is removed from the configured NIC. Thus, the Arbitration service may be managing several floating IP addresses at any given time.

A single instance of the Arbitration service is capable of supporting several arbitrated services installed on the same server. For example, if the RealTime and Historical services installed on a server has a redundant server, then a single Arbitration service installed on each server will control the RealTime and Historical service states. Only one instance of an Arbitrated service (such as RealTime) is installed per server, as failovers are supported between services running on different servers.

This service is separate from the underlying services because the operation of adding and removing the floating IP demands increased security capabilities for the given computer. Specifically, the process responsible for adding and removing the floating IP must run as the SYSTEM account. By contrast, every other AVEVA Enterprise SCADA Service is expected to run as the dnaApp user, who has fewer security privileges than the SYSTEM account. By separating this layer, AVEVA Enterprise SCADA is employing the best practice for security by reducing the security capabilities to only those that are absolutely necessary for a given service.