System information

Hardware
Asterisk is capable of communicating with a vast number of different technologies. In
general, these connections are made across a network connection; however, connec-
tions to more traditional telecom technologies, such as the PSTN, require specific
hardware.
Many companies produce this hardware, such as Digium (the sponsor, owner, and
primary developer of Asterisk), Sangoma, Rhino, OpenVox, Pika, Voicetronix,
Junghanns, Dialogic, Xorcom, beroNet, and many others. The authors prefer cards
from Digium and Sangoma; however, the products offered by other Asterisk hardware
manufacturers may be more suitable to your requirements.
The most popular hardware for Asterisk is generally designed to work through the
Digium Asterisk Hardware Device Interface (known as DAHDI). These cards will all
have different installation requirements and different file locations.
In Chapter 7, we will discuss DAHDI in more detail; however, we will limit our dis-
cussion to DAHDI only. You will need to refer to the specific documentation provided
by the manufacturers of any cards you install for details on those cards.
Asterisk Versioning
The Asterisk release methodology has gone through a couple of iterations over the last
few years, and this section is designed to help you understand what the version numbers
mean. Of particular relevance is the change in versioning that happened with the
1.6.x series of releases, which followed a different numbering logic than all other
Asterisk releases (1.0 to 1.8 and onward for the foreseeable future).
Previous Release Methodologies
When we had just Asterisk 1.2 and 1.4, all new development was carried out in trunk
(it still is), and only bug fixes went into the 1.2 and 1.4 branches. The Asterisk 1.2
branch has been marked as EOL (End of Life), and is no longer receiving bug fixes or
security updates. Prior to the 1.6.x branches, bug fixes were carried out only in trunk
and in the 1.4 branch.
Because all new development was done in trunk, until the 1.6 branch was created people
were unable to get access to the new features and functionality. This isn’t to say the
new functionality wasn’t available, but with all the changes that can happen in trunk,
running a production server based on it requires a very Asterisk-savvy (and C code–
savvy) administrator.
To try to relieve the pressure on administrators, and to enable faster access to new
features (in the time frame of months, and not years), a new methodology was created.
Branches in 1.6 would actually be marked as 1.6.0, 1.6.1, 1.6.2, etc., with the third
26 | Chapter 2: Asterisk Architecture
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