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Closing Thoughts

How To: Building an Embedded Asterisk PBX
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Most of my experience with Astlinux on the Soekris platform has been with using version 0.28, which is based upon a very stable Asterisk v1.09 release from Jan 10, 2005. Kristian released version 0.29 recently, which encompasses the newer Asterisk v1.2 release from October 2005. By the time you read this review, Kristian may well be on release v0.30, which is projected to be a thoroughly tested Astlinux implementation including Asterisk v1.2 and support for some new hardware drivers. However, changes in Asterisk's core dial plan logic behavior kept me from trying the new release within the context of this review.

Kristian also made news at Astricon 2005 by successfully porting Astlinux to the Gumstix embedded SBC platform. Called TinyPBX, this combination was heralded as the "World's Smallest VoIP PBX."

The initial application of such a small Asterisk system was as a protocol translator, allowing common SIP desk phones to be easily adapted to use the IAX2 protocol native to Asterisk. Unlike SIP, IAX2 streams combine call setup signaling and the voice data stream into a single connection that easily traverses NAT routers and firewalls. The combination of a Gumstix based translator with SIP desk phones allows for the creation of distributed phone systems ideal for companies with many home office based employees, or for connecting several smaller offices into one primary Asterisk server. Using IAX2 instead of SIP permits this with a minimum of network setup and support complexity.

Astlinux has proven to be a valuable tool around my home office. It provides the power and flexibility of an Asterisk installation with the reliability and simplicity of an embedded system. It may not provide the comfort of a graphical administration scheme, but it suffers none of the overhead or setup limitations of common GUI overlays.

The Soekris Net4801, while inexpensive, has been absolutely reliable as a host platform, delivering adequate processing power to support six extensions and up to four active lines at one time. It could perhaps do more, but such was beyond the scope of my ability to test.

Together, Astlinux and the Soekris Net4801 represent an elegant D.I.Y. approach to deploying an iPBX in a home or small office setting.

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