Redundancy and Load Balancing

The following sections describe WebLogic Network Gatekeeper high availability and load balancing features:

Applications to network nodes fault tolerance

Fault tolerance downstream is defined as the ability of the WebLogic Network Gatekeeper to hide that an WebLogic Network Gatekeeper software module or server has become unavailable, and seamlessly switch over the service execution to other software module instances.

Fault tolerance upstream is defined as the ability for the WebLogic Network Gatekeeper to provide network triggered events from the a service capability in the network to a subscribing application even if an WebLogic Network Gatekeeper software module or server becomes unavailable.

Three areas are identified as key areas when it comes to provide fault tolerance:

Preservation of listeners, states and sessions.
High availability and load balancing between software modules.
Overall platform robustness

Preservation of listeners, states and sessions

The WebLogic Network Gatekeeper implements different levels of fault tolerance for different service capabilities. Below follows a description of these mechanisms for the affected service capabilities.

Call		All notification listeners are preserved.
Charging		A charging session that has been lost can be can be retrieved as long as the ID, given when the session was created, is known.
Messaging		All open mailboxes are preserved. Likewise are the states of all folders preserved. All operations defined for the manager, the mailboxes and the folders are available and the applications can use these seamlessly. All notification listeners are preserved.

High availability and load balancing between software modules

The WebLogic Network Gatekeeper provides high availability and load balancing between software modules in all layers, see Figure 17-1.

ha_ft_lb.html

The load balancing and high availability mechanisms implemented in each software module are described in Software Module Descriptions.

Platform robustness

The WebLogic Network Gatekeeper itself is built on a carrier grade platform in order to allow high availability for the executing applications. For more information, see Hardware Architecture.