High Availability is designed to eliminate a single point of failure in a network configuration. Two systems can be configured to act as a redundant pair. One of the systems is the designated Primary system, the other is the designated Secondary system. Normally, the Primary system is the Active system and the Secondary system is the Standby system.

If the Primary system fails because of a network or hardware failure, the Secondary system will take over and become the new Active system.

Stateful Failover

Stateful failover is a high availability feature that transfers state between two systems so that active calls will not be terminated during an activity switch. Stateful failover was designed to support SIP trunking applications only and should only be configured in systems using an Ethernet LAN and WAN. Other applications that require additional call state (for example, multi-line appearances for IP phones as used in Hosted PBX applications) may not work correctly upon an activity switch. For these applications, as well as applications using H.323 over TCP, an activity switch will still occur but the voice or video calls may need to be re-established.

B2BUA High Availability

The B2BUA HA feature allows the calls connected through B2BUA to continue seamlessly during and after a system failover. Calls that are already established stay active during system failure. New calls can be established successfully after system failure. This feature works with UDP and TCP protocols, assuming the remote devices supports new TCP connections during a call.

This feature is enabled automatically when HA and state transfer are enabled and is supported on the EdgeMarc 2900, 4800 Series, 6000, and 7000 Series platforms.