Large contact center deployment can start with an install base of few hundred seats, going all the way to thousand plus seats. Using “number of concurrent calls” is a better measure of the capacity of the contact center platform but many legacy manufacturers use agent seat counts for licensing purposes. In inbound call centers with ACD (Automatic Call Distribution) Queues and Skills based Routing, the total number of concurrent calls might be set to some percentage about the available concurrent agents, depending on average call duration and the Service Level Agreement (SLA) mandate. The upper threshold for the maximum number of concurrent calls for a call center setup might be imposed by the limitations of the technology platform due to two main reasons.

At a telecom level, the phone switch (which is the media server for voice traffic) could impose an upper limit. A good contact center software will scale to multiple telephone switches and the workaround this limitation is straightforward. Take the case of Asterisk, the leading open source telephone switch serving both the TDM and the VoIP segments with its hybrid telephone soft switch. Though factors like enabling voice recording and codec compression limit the maximum number, Asterisk can typically process hundreds of concurrent calls. For larger installs, the call center ACD should be capable of scaling to multiple Asterisk servers to provide the required capacity. Many of the higher end contact center solutions will come with a SIP Proxy which will effectively load balance between multiple Asterisk servers.

The Call Center ACD may also have an upper limit. It is absolutely essential that the multi-channel ACD be a separate entity, to manage queuing and routing from the media (Voice, E-Mail, Web, Chat) servers.  The ACD is responsible for managing queuing and prioritization with Skills based routing and Queue priority. The upper limit on the processing capability of an ACD may impose restriction on queues and queue length. Given the state of processing power of the modern hardware, a single ACD can serve thousand concurrent calls and more. It is also possible to combine multiple ACD units to function together if the total call count is spread over different queues.

It is time to take advantage of Asterisk by using advanced call center suites to build very large multi-channel contact center operations to take control of the cost.