The solution must be based on software or hardware load balancer in the customer's network (black box Failover and Load balancing). The unit of failover and load balancing is one Spooler Controller Group. The Spooler Controller Group is represented from the perspective of MFDs by one and only one virtual IP address or FQDN (reverse lookups have to be configured) which is held by the load balancer. This virtual address will be used by MFDs and Dispatcher Paragon Terminals.

Following requirements are expected to be delivered by the load balancer for Terminal Failover:

• It shall make failover decision based on the state of appropriate Windows Services as reported by Service Control Manager of individual servers running SPOC/TS services AND/OR based on the availability of selected TCP ports. If TCP based monitor is in place, required ports for monitoring are 5555 (for SPOC service) and 5022 (for TS service). The TCP monitor must finish connection after SYN - ACK with RST, not with FIN. Our recommendation for monitoring period is 5 seconds with node considered down after 3 unsuccessful attempts. Node shall not be considered up immediately but after defined time which must be based on real time required for Management/Site Server to start.
• The load balancer shall honor affinity between MFDs and particular SPOC/TS service instances in the Spooler Controller Group based on the prior decisions made by the load balancer and configurable timeout window. I.e., when the load balancer decides to connect an MFD with a particular SPOC/TS service, it must connect the MFD to the same SPOC/TS service if connection (incl. DNS lookup) attempts are made by the MFD before the configurable timeout elapses. Affinity needs to be set for a minimum of 30 minutes.
  
• The load balancer shall distribute requests among SPOC/TS nodes in the Spooler Controller Group uniformly.
• The load balancer shall distribute requests from MFDs to SPOC/TS based on Network Communication (typically TCP ports 5011 - 5025 and ports for FTP/WebDAV)
  
• The load balancer shall handle monitoring and reporting of the service failures on its own.
• All inbound communication to SPOC/TS from a single user session (thus from single MFD) must appear under a single source IP address (e.g. load balancer may mask MFD IP address, but the same masked IP must be used throughout the session; it should not happen that one time the IP address of MFD is visible, one time the IP address of load balancer and next time for example the secondary IP address of load balancer).