ACD (Automatic Call Distribution)
The logic that decides which waiting call goes to which free agent.
ACD stands for Automatic Call Distribution: the logic that decides which waiting call goes to which free agent. Every inbound phone system has one. In VICIdial the ACD is not a separate component - it is the behaviour of the in-group, configured per queue.
The two decisions
An ACD answers two questions on every call, and they are worth keeping separate in your head.
Which call next? When more than one call is waiting, queue_priority on the in-group decides which queue an agent is served from first. Within a queue, calls are taken in arrival order.
Which agent? next_agent_call on the in-group picks the agent. It defaults to longest_wait_time - the agent who has been idle longest - which is the fair, even-distribution choice. The alternatives select on agent rank, on fewest calls handled, or at random. Rank-based selection is how you send calls preferentially to your strongest people; longest-idle is how you spread load evenly.
Agent-side weighting lives on vicidial_inbound_group_agents, where group_rank, group_weight and group_grade set an agent's standing within a specific in-group, and daily_limit caps how many calls they take from it.
Skills routing, VICIdial-style
There is no skills table in VICIdial. Skills-based routing is built out of in-group membership: create an in-group per skill, put the qualifying agents in it, rank them, and route calls to the right queue at the front door with a call menu or DID. An agent who belongs to several in-groups is effectively multi-skilled, and queue_priority decides which of their skills is served first when both queues are busy.
Choosing a strategy
Start with longest_wait_time. It is the default for good reason: it distributes work evenly, keeps everyone warm, and gives you clean per-agent numbers to compare. Move to rank-based selection only once you have a measured reason - a conversion difference large enough to justify concentrating calls, and enough volume that the top-ranked agents will not simply become the bottleneck.