System information

Figure 2-1. Asterisk vs. PBX architecture
Modules
Asterisk is built on modules. A module is a loadable component that provides a specific
functionality, such as a channel driver (for example, chan_sip.so), or a resource that
allows connection to an external technology (such as func_odbc.so). Asterisk modules
are loaded based on the /etc/asterisk/modules.conf file. We will discuss the use of many
modules in this book. At this point we just want to introduce the concept of modules,
and give you a feel for the types of modules that are available.
It is actually possible to start Asterisk without any modules at all, although in this state
it will not be capable of doing anything. It is useful to understand the modular nature
of Asterisk in order to appreciate the architecture.
You can start Asterisk with no modules loaded by default and load each
desired module manually from the console, but this is not something
that you’d want to put into production; it would only be useful if you
were performance-tuning a system where you wanted to eliminate ev-
erything not required by your specific application of Asterisk.
The types of modules in Asterisk include the following:
• Applications
• Bridging modules
• Call detail recording (CDR) modules
• Channel event logging (CEL) modules
10 | Chapter 2: Asterisk Architecture