5.1. Telephone Naming Concepts

Before we get started with configuring Asterisk for our telephones, we are going to recommend some best practices regarding telephone naming, abstracting the concepts of users, extension numbers, and telephones from each other.

In Asterisk, all the system cares about is the channel name. There is really no concept of a user at all,^[58] and extensions are simply ways of directing call flow through the system. For example, your dialplan might inform Asterisk that when extension number 100 is requested it should call the phone on my desk, but extension 100 could just as easily call a company voicemail box, play back a prompt, or join a conference room. We can even specify that extension 100 should ring the device on my desk from Monday to Friday between 9 A.M. and 5 P.M., but ring a device on someone else’s desk the rest of the time. Inversely, when a call is made from a device during business hours, the callerID could show a daytime number, and the rest of the time could show an after-hours number (many reception desks become security desks at night).

^[58] Actually, Asterisk does try to implement and abstract the concepts of users and devices internally by using the users.conf file; however, it is typically only used by the Asterisk GUI. Abstracting the concepts logically using the dialplan is easier to understand and far more flexible.