Converged Load Balancer

The converged load balancer accepts both HTTP/HTTPS and SIP/SIPS requests and forwards them to application server instances in a cluster. If an instance fails, becomes unavailable (due to network faults), or becomes unresponsive, the load balancer redirects requests to existing, available machines. The load balancer can also recognize when a failed instance has recovered and redistribute the load accordingly. Communications Server provides the converged load balancer. A cluster (of Communications Server instances) or a standalone instance can be a dedicated load balancer. Each instance in a cluster can participate in load balancing, in which case the cluster is self-load-balancing.

By distributing workload among multiple physical machines, the load balancer increases overall system throughput. It also provides higher availability through failover of HTTP and SIP requests. The converged load balancer also helps achieve scalability of a system deployment. For HTTP and SIP session information to persist, you must configure session persistence.

For simple, stateless applications, a load-balanced cluster may be sufficient. However, for mission-critical applications with session state, use load balanced clusters with replicated session persistence.

Server instances and clusters participating in load balancing must have a homogenous environment.

For information on configuring load balancing and failover for the converged load balancer, see Chapter 2, Configuring Converged Load Balancing.