Queues are the back-bone of a modern ACD (Automatic Call Distribution). Within any sophisticated call center software, Queuing is an abstraction of the information that represents all the various parameters and attributes of Queues and Calls. Queue management is the ability to efficiently distribute calls to the most appropriate Agent in a Call Center or an organization. The separation of queuing and queue management from the actual calls is a natural progression in the evolution of ACD. Skills based routing, Queue Priority and many other Queue manipulation features are a by-product of this progression.
Media, whether it is Voice, E-mail, Chat or any other type is handled by the respective media server. For example, voice calls are handled by a PBX where as the Queuing is handled by an ACD. It is essential for an ACD to have this separation between Queuing and Media. In a true multi-channel ACD setup, the next requirement is the ability to insert any media call into the right Queue. Voice telephony has been intrinsic to ACD evolution and therefore most PBX like Asterisk can be setup to inform the Call Center ACD of an incoming voice call with the attributes. For other media type, a multi-channel ACD will be capable of accepting into a specific queue, a trigger from the respective media server through an API with media type, unique ID and other parameters.
The last aspect is how the media is served to an Agent. E-Mail is like Voice and is better handled sequentially. Chat is slower and multiple Chat conversations can be handled by an Agent in parallel. All this has impact on how different media types are queued and served to Agents. Sophisticated ACD like Q-Suite for Asterisk based call centers have built-in support for multi-channel media to provide unified queuing.