A call is normally thought of as a communication between two or more parties, across a set of communication facilities, and it is natural to think of those parties as the endpoints involved in the call. In fact, such parties are sometimes referred to as terminals, and they can include telephones, fax machines, voice recorders, IVRs (Interactive Voice Response units), and video devices. However, the term endpoint can also be used in certain circumstances to include facilities that do not represent the true points of termination of a call (most notably, trunks).

We use the term station to refer to a device being used by human beings in real-time to originate and receive calls (including voice calls, faxes, and text messaging). Such devices include circuit-switched telephones, H.323 hardphones and softphones, SIP hardphones and softphones, and fax machines. The people using them are referred to as users.

When referring to a domain such as an Avaya Aura® enterprise solution or a particular Communication Manager system, the term station is only used to refer to stations within that domain. For example, when performing traffic analysis on a particular Avaya Aura® enterprise, telephones in the PSTN are not considered to be stations in that enterprise. This represents a circumstance in which trunks are referred to as endpoints from the perspective of the enterprise of interest, even though they are not true points of call termination.

Normally, the set of enterprise configuration inputs includes a specification of the quantity, physical location, and logical association (for example, network region) of each type of station to be used in a particular enterprise. In some cases, the number of trunks is also specified, while in others, the number of trunks must be calculated as an output of the traffic-engineering process.