Page 66 - Asterisk™: The Future of Telephony

What Packages Do I Need?

Most Asterisk configurations are composed of three main packages : the main Asterisk
program (asterisk), the Zapata telephony drivers (zaptel), and the PRI libraries (libpri).
If you plan on a pure VoIP network, the only real requirement is the asterisk package,
but we recommend installing all three packages; you can choose what modules to ac-
tivate later. The zaptel drivers are required if you are using analog or digital hardware,
or if you’re using the ztdummy driver (discussed later in this chapter) as a timing source.
The libpri library is optional unless you’re using ISDN PRI interfaces, and you may save
a small amount of RAM if you don’t load it, but we recommend that it be installed in
conjunction with the zaptel package for completeness.
In the first edition of this book, we recommended that you install the additional
asterisk-sounds package. This was a separate compressed archive that you would
download, extract, and then install. As of Asterisk version 1.4.0, there are now two sets
of sounds packages: the Core Sound package and the Extra Sound package. Since As-
terisk supports several different audio formats, these packages can be obtained in a
number of different sound formats, such as G.729 and GSM. The reason for all of the
different formats is that Asterisk can use the sound format that requires the least amount
of CPU transcode. For example, if you have a lot of connections coming in on VoIP
channels that are running GSM, you would want to have the GSM version of the sound
files. You can select one or more sound prompt types in the menuselect screen (dis-
cussed later in this chapter). We recommend that you install at least one type of sounds
file from both the Core Sound package and Extra Sound package menu items. Since
we may make use of some of the Extra Sound files throughout this book, we will assume
you have at least one of the formats installed.

Linux Package Requirements
To compile Asterisk, you must have the GCC compiler (version 3.x or later) and its
dependencies on your system. Asterisk also requires bison, a parser generator program
that replaces yacc, and ncurses for CLI functionality. The cryptographic library in As-
terisk requires OpenSSL and its development packages.
Zaptel requires libnewt and its development packages for the zttool program (see “Using
ztcfg and zttool later in this chapter). If you’re using PRI interfaces, Zaptel also requires
the libpri package (again, even if you aren’t using PRI circuits, we recommend that you
install libpri along with zaptel).
If you install the Software Development packages in CentOS, you will have all of these
tools. If you are looking to keep things trim, and wish to install the bare minimum to
compile Asterisk and its related packages, Table 3-1 will prove useful.

38 | Chapter 3: Installing Asterisk