Network Dispatcher High Availability

Availability is crucial to handling Internet traffic. Slow responses or refused connections create unsatisfied users. Network Dispatcher has superior load balancing, scalability, AND high availability.

Network Dispatcher can be configured to use a standby machine, on the same subnet, that remains ready at all times to take over load balancing if the primary Dispatcher machine fails. The high availability feature uses a "heartbeat" mechanism between the two Dispatchers to detect failure. The two Dispatchers have connectivity to the same clients, and the same cluster of servers, as well as connectivity between the Dispatchers. The Dispatchers synchronize information, and have built-in logic to elect the active Dispatcher that is in charge of a given cluster of servers; the standby Dispatcher is continuously synchronized for that cluster of servers.

The customer-defined "reachability" criteria identifies what can and what cannot be reached from the Dispatcher, such as access to gateway routers across duplicated adapters and networks. If the heartbeat fails, or defined reachability criteria are not met, the primary Dispatcher is deemed to be down, and the standby Dispatcher takes over forwarding packets. (Typically, the failover process will take less than five seconds, minimizing possible connection failures.)

Network Dispatcher has a mechanism to perform fast IP takeover when the logic, or an operator, decides to switch active and standby Dispatchers.


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