In larger installations with high concurrent call volume, the contact center ACD manages and controls multiple Asterisk servers in a cluster. Since call volume at any given instant can exceed the capacity of a single Asterisk server, a SIP proxy will serve to distribute calls evenly with load balancing. The ACD maintains the sequence and order of calls coming to the individual queues, irrespective of the Asterisk servers into which the calls come in. It will route and distribute calls to the available agents based on skills based routing, irrespective of where their phones are registered to. Sophisticated call center solutions offer greater flexibility allowing agents to use any external phone like home land-line phone or a mobile phone or a phone behind another PBX. This is ideal for remote and work-at-home options.
The SIP proxy can also play a part in the High availability setup designed for fail-over to redundant available systems. The same SIP proxy also provides the required load balancing to distribute calls within the Asterisk cluster. A simple round-robin load balancing is often the default option unless there is a clear need for a “weighted” algorithm to dynamically control the call distribution. In a sophisticated High Availability options with Call Survival offered by Q-Suite, there is already a communication channel between the Contact Center ACD and the High Availability SIP proxy. This allows opportunity for the Contact Center ACD to use call statistics and related information to control the load balancing.