Page 39 - Asterisk™: The Future of Telephony

CHAPTER 2

Preparing a System for Asterisk

Very early on, I knew that someday in some “perfect”
future out there over the horizon, it would be common-
place for computers to handle all of the necessary pro-
cessing functionality internally, making the necessary
external hardware to connect up to telecom interfaces
very inexpensive and, in some cases, trivial.
—Jim Dixon, “The History of Zapata Telephony and
How It Relates to the Asterisk PBX”

By this point, you must be anxious to get your Asterisk system up and running. If you
are building a hobby system, you can probably jump right to the next chapter and begin
the installation. For a mission-critical deployment, however, some thought must be
given to the environment in which the Asterisk system will run. Make no mistake:
Asterisk, being a very flexible piece of software, will happily and successfully install on
nearly any Linux platform you can conceive of, and several non-Linux platforms as
*
well. However, to arm you with an understanding of the type of operating environment
Asterisk will really thrive in, this chapter will discuss issues you need to be aware of in
order to deliver a reliable, well-designed system.
In terms of its resource requirements, Asterisk’s needs are similar to those of an em-
bedded, real-time application. This is due in large part to its need to have priority access
to the processor and system buses. It is, therefore, imperative that any functions on the
system not directly related to the call-processing tasks of Asterisk be run at a low pri-
ority, if at all. On smaller systems and hobby systems, this might not be as much of an
issue. However, on high-capacity systems, performance shortcomings will manifest as
audio quality problems for users, often experienced as echo, static, and the like. The
symptoms will resemble those experienced on a cell phone when going out of range,

* People have successfully compiled and run Asterisk on WRAP boards, Linksys WRT54G routers, Soekris
systems, Pentium 100s, PDAs, Apple Macs, Sun SPARCs, laptops, and more. Of course, whether you would
want to put such a system into production is another matter entirely. (Actually, the AstLinux distribution,
by Kristian Kielhofner, runs very well indeed on the Soekris 4801 board. Once you’ve grasped the basics of
Asterisk, this is something worth looking into further. Check out http://www.astlinux.org.)

11