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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>The Promise of Open Source Telephony</title><link rel="stylesheet" href="styles.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /><link rel="start" href="index.html" title="Asterisk™: The Future of Telephony" /><link rel="up" href="asterisk-CHP-15.html" title="Chapter 15. Asterisk: The Future of Telephony" /><link rel="prev" href="asterisk-CHP-15-SECT-2.html" title="Paradigm Shift" /><link rel="next" href="asterisk-CHP-15-SECT-4.html" title="The Future of Asterisk" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">The Promise of Open Source Telephony</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="asterisk-CHP-15-SECT-2.html">Prev</a> </td><th width="60%" align="center">Chapter 15. Asterisk: The Future of Telephony</th><td width="20%" align="right"> <a accesskey="n" href="asterisk-CHP-15-SECT-4.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="asterisk-CHP-15-SECT-3"></a>The Promise of Open Source Telephony</h2></div></div></div><div class="epigraph"><p>Every good work of software starts by scratching a developer’s
personal itch.</p><div class="attribution"><span>--<span class="attribution">Eric S. Raymond, <span class="emphasis"><em>The Cathedral and the
Bazaar</em></span></span></span></div></div><p>In his book<a id="I_indexterm15_tt1761" class="indexterm"></a><a id="I_indexterm15_tt1762" class="indexterm"></a> <span class="emphasis"><em>The Cathedral and the Bazaar</em></span>
(O’Reilly), Eric S. Raymond explains that “Given enough eyeballs, all bugs
are shallow.” The reason open source software development produces such
consistent quality is simple: crap can’t hide.</p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="asterisk-CHP-15-SECT-3.1"></a>The Itch That Asterisk Scratches</h3></div></div></div><p>In this era of custom database and web site development, people
are not only tired of hearing that their telephone system “can’t do
that,” they quite frankly just don’t believe it. The creative needs of
the customers, coupled with the limitations of the technology, have
spawned a type of creativity born of necessity: telecom engineers are
like <span class="keep-together">contestants</span> in an episode of
<span class="emphasis"><em>Junkyard Wars</em></span>, trying to create functional devices
out of a pile of mismatched components.</p><p>The development methodology of a proprietary telephone system
dictates that it will have a huge number of features, and that the
number of features will in large part determine the price. Manufacturers
will tell you that their products give you hundreds of features, but if
you only need five of them, who cares? Worse, if there’s one missing
feature you really can’t do without, the value of that system will be
diluted by the fact that it can’t completely address your needs.</p><p>The fact that a customer might only need 5 out of 500 features is
ignored, and that customer’s desire to have 5 unavailable features that
address the needs of his business is dismissed as unreasonable.<sup>[<a id="asterisk-CHP-15-FN-5" href="#ftn.asterisk-CHP-15-FN-5">155</a>]</sup> Until flexibility becomes standard, telecom will remain
stuck in the last century—all the VoIP in the world
notwithstanding.</p><p>Asterisk addresses that problem directly and solves it in a way
that few other telecom systems can. This is extremely disruptive
technology, in large part because it is based on concepts that have been
proven time and time again: “the closed-source world cannot win an
evolutionary arms race with open-source communities that can put orders
of magnitude more skilled time into a problem.”<sup>[<a id="asterisk-CHP-15-FN-6" href="#ftn.asterisk-CHP-15-FN-6">156</a>]</sup></p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="asterisk-CHP-15-SECT-3.2"></a>Open Architecture</h3></div></div></div><p>One of the stumbling<a id="I_indexterm15_tt1763" class="indexterm"></a> blocks of the traditional telecommunications industry has
been its apparent refusal to cooperate with itself. The big
telecommunications giants have all been around for over a hundred years.
The concept of closed, proprietary systems is so ingrained in their
culture that even their attempts at standards compliancy are tainted by
their desire to get the jump on the competition, by adding that one
feature that no one else supports. For an example of this thinking, one
simply has to look at the VoIP products being offered by the telecom
industry today. While they claim standards compliance, the thought that
you would actually expect to be able to connect a Cisco phone to a
Nortel switch, or that an Avaya voicemail system could be integrated via
IP to a Siemens PBX, is not one that bears discussing.</p><p>In the computer industry, things are different. Twenty years ago,
if you bought an IBM server, you needed an IBM network and IBM terminals
to talk to it. Now, that IBM server is likely to interconnect to Dell
terminals though a Cisco network (and run Linux, of all things). Anyone
can easily think of thousands of variations on this theme. If any one of
these companies were to suggest that we could only use their products
with whatever they told us, they would be laughed out of
business.</p><p>The telecommunications industry is facing the same changes, but
it’s in no hurry to accept them. Asterisk, on the other hand, is in a
big hurry to not only accept change, but embrace it.</p><p>Cisco, Nortel, Avaya, and Polycom IP phones (to name just a few)
have all been successfully connected to Asterisk systems. There is no
other PBX in the world today that can make this claim. None.</p><p><span class="emphasis"><em>Openness is the power of Asterisk</em></span>.</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="asterisk-CHP-15-SECT-3.3"></a>Standards Compliance</h3></div></div></div><p>In the past few years, it has become clear that standards evolve
at such a rapid pace that to keep up with them requires an ability to
quickly respond to emerging technology trends. Asterisk, by virtue of
being an open source, community-driven development effort, is uniquely
suited to the kind of rapid development that standards compliance
demands.</p><p>Asterisk does not focus on cost-benefit analysis or market
research. It evolves in response to whatever the community finds
exciting—or necessary.</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="asterisk-CHP-15-SECT-3.4"></a>Lightning-Fast Response to New Technologies</h3></div></div></div><p>After Mark Spencer attended his first SIP Interoperability Test
(SIPIT) event, he had a rudimentary but working SIP stack for Asterisk
coded within a few days. This was before SIP had emerged as the protocol
of choice in the VoIP world, but he saw its value and momentum and
ensured that Asterisk would be ready.</p><p>This kind of foresight and flexibility is typical in an open
source development community (and very unusual in a large
corporation).</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="asterisk-CHP-15-SECT-3.5"></a>Passionate Community</h3></div></div></div><p>The <span class="emphasis"><em>Asterisk-users</em></span> list receives many email
messages per day. More than 10,000 people are subscribed to it. This
kind of community support is unheard of in the world of proprietary
telecommunications, while in the open source world it is
commonplace.</p><p>The very first AstriCon event was expected to attract 100
participants. Nearly 500 showed up (far more wanted to but couldn’t
attend). This kind of community support virtually guarantees the success
of an open source effort.</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="asterisk-CHP-15-SECT-3.6"></a>Some Things That Are Now Possible</h3></div></div></div><p>So what sorts of things can be built using Asterisk? Let’s look at
some of the things we’ve come up with.</p><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="asterisk-CHP-15-SECT-3.6.1"></a>Legacy PBX migration gateway</h4></div></div></div><p>Asterisk can <a id="I_indexterm15_tt1764" class="indexterm"></a>be used as a fantastic bridge between an old PBX and the
future. You can place it in front of the PBX as a gateway (and migrate
users off the PBX as needs dictate), or you can put it behind the PBX
as a peripheral application server. You can even do both at the same
time, as shown in <a href="asterisk-CHP-15-SECT-3.html#asterisk-CHP-15-FIG-1" title="Figure 15.1. Asterisk as a PBX gateway">Figure 15.1, “Asterisk as a PBX gateway”</a>.</p><div class="figure"><a id="asterisk-CHP-15-FIG-1"></a><p class="title"><b>Figure 15.1. Asterisk as a PBX gateway</b></p><div class="mediaobject"><a id="I_mediaobject15_tt1765"></a><img src="figs/web/ast2_1501.png" alt="Asterisk as a PBX gateway" /></div></div><p>Here are some of the options you can implement:</p><div class="variablelist"><dl><dt><span class="term">
<span class="emphasis"><em>Keep your old PBX, but evolve to
IP</em></span>
</span></dt><dd><p>Companies that have spent vast sums of money in the past
few years buying proprietary PBX equipment want a way out of
proprietary jail, but they can’t stomach the thought of throwing
away all of their otherwise functioning equipment. No
problem—Asterisk can solve all kinds of dilemmas, from replacing
a voicemail system to providing a way to add IP-based users
beyond the nominal capacity of the system.</p></dd><dt><span class="term">
<span class="emphasis"><em>Find-me-follow-me</em></span>
</span></dt><dd><p>Provide the PBX a list of numbers where you can be
reached, and it will ring them all whenever a call to your DID
(Direct Inward Dialing, a.k.a. phone number) arrives. <a href="asterisk-CHP-15-SECT-3.html#asterisk-CHP-15-FIG-2" title="Figure 15.2. Find-me-follow-me">Figure 15.2, “Find-me-follow-me”</a> illustrates this
technology.</p></dd><dt><span class="term">
<span class="emphasis"><em>VoIP calling</em></span>
</span></dt><dd><p>If a legacy telephony connection from an Asterisk PBX to
an old PBX can be established, Asterisk can provide access to
VoIP services, while the old PBX continues to connect to the
outside world as it always has. As a gateway, Asterisk simply
needs to emulate the functions of the PSTN, and the old PBX
won’t know that anything has changed. <a href="asterisk-CHP-15-SECT-3.html#asterisk-CHP-15-FIG-3" title="Figure 15.3. VoIP-enabling a legacy PBX">Figure 15.3, “VoIP-enabling a legacy PBX”</a> shows how you can use
Asterisk to VoIP-enable a legacy PBX.</p></dd></dl></div><div class="figure"><a id="asterisk-CHP-15-FIG-2"></a><p class="title"><b>Figure 15.2. Find-me-follow-me</b></p><div class="mediaobject"><a id="I_mediaobject15_tt1766"></a><img src="figs/web/ast2_1502.png" alt="Find-me-follow-me" /></div></div><div class="figure"><a id="asterisk-CHP-15-FIG-3"></a><p class="title"><b>Figure 15.3. VoIP-enabling a legacy PBX</b></p><div class="mediaobject"><a id="I_mediaobject15_tt1767"></a><img src="figs/web/ast2_1503.png" alt="VoIP-enabling a legacy PBX" /></div></div></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="asterisk-CHP-15-SECT-3.6.2"></a>Low-barrier IVR</h4></div></div></div><p>Many people confuse the term<a id="I_indexterm15_tt1768" class="indexterm"></a><a id="I_indexterm15_tt1769" class="indexterm"></a> “Interactive Voice Response,” or IVR, with the
Automated Attendant (AA). Since the Automated Attendant was the very
first thing IVR was used for, this is understandable. Nevertheless, to
the telecom industry, the term IVR represents far more than an AA. An
AA generally does little more than present a way for callers to be
transferred to extensions, and it is built into most proprietary
voicemail systems—but IVR can be so much more.</p><p>IVR systems are generally very expensive not only to purchase,
but also to configure. A custom IVR system will usually require
connectivity to an external database or application. Asterisk is
arguably the perfect IVR, as it embraces the concepts of connectivity
to databases and applications at its deepest level.</p><p>Here are a few examples of relatively simple IVRs that an
Asterisk system could be used to create:</p><div class="variablelist"><dl><dt><span class="term">
<span class="emphasis"><em>Weather reporting</em></span>
</span></dt><dd><p>Using the Internet, you can obtain text-based weather
reports from around the world in a myriad of ways. Capturing
these reports and running them through a purpose-built parser
(Perl would probably eat this up) would allow the information to
be available to the dialplan. Asterisk’s sound library already
contains all of the required prompts, so it would not be an
onerous task to produce an interactive menu to play current
forecasts for anywhere in the world.</p></dd><dt><span class="term">
<span class="emphasis"><em>Math programs</em></span>
</span></dt><dd><p>Ed Guy (the architect of Pulver’s FWD network) did a
presentation at AstriCon 2004 in which he talked about a little
math program he’d cooked up for his daughter to use. The program
took him no more than an hour to write. What it did was present
her with a number of math questions, the answers to which she
keyed into the telephone. When all the questions were tabulated,
the system presented her with her score. This extremely simple
Asterisk application would cost tens of thousands of dollars to
implement on any closed PBX platform, assuming it could be done
at all. See <a href="asterisk-CHP-9.html" title="Chapter 9. The Asterisk Gateway Interface (AGI)">Chapter 9, <i>The Asterisk Gateway Interface (AGI)</i></a> for further
details. As is so often the case, things that are simple for
Asterisk would be either impossible or massively expensive with
any other IVR system.</p></dd><dt><span class="term">
<span class="emphasis"><em>Distributed IVR</em></span>
</span></dt><dd><p>The cost of a proprietary IVR system is such that when a
company with many small retail locations wants to provide IVR,
it is forced to transfer callers to a central server to process
the transactions. With Asterisk, it becomes possible to
distribute the application to each node and, thus, handle the
requests locally. Literally thousands of little Asterisk systems
deployed at retail locations across the world could serve up IVR
functionality in a way that would be impossible to achieve with
any other system. No more long-distance transfers to a central
IVR server, no more huge trunking facility dedicated to the
task—more power with less expense.</p></dd></dl></div><p>These are three rather simple examples of the potential of
Asterisk.</p></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="asterisk-CHP-15-SECT-3.6.3"></a>Conference rooms</h4></div></div></div><p>This little gem is going to end up being one of the killer
functions of Asterisk. In the Asterisk community, everyone finds
themselves using conference rooms more and more, for purposes such as
these:</p><div class="itemizedlist"><ul type="disc"><li><p>Small companies need an easy way for business partners to
get together for a chat.</p></li><li><p>Sales teams have a meeting once per week where everyone can
dial in from wherever they are.</p></li><li><p>Development teams designate a common place and time to
update one another on progress.</p></li></ul></div></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="asterisk-CHP-15-SECT-3.6.4"></a>Home automation</h4></div></div></div><p>Asterisk is still too much of an über-geek’s tool to be able to
serve in the average home, but with no more than average Linux and
Asterisk skills, the following things become plausible:</p><div class="variablelist"><dl><dt><span class="term">
<span class="emphasis"><em>Monitoring the kids</em></span>
</span></dt><dd><p>Parents who want to check up on the babysitter (or the
kids home alone) could dial an extension context protected by a
password. Once authenticated, a two-way audio connection would
be created to all the IP phones in the house, allowing Mom and
Dad to listen for trouble. Creepy? Yes. But an interesting
concept nonetheless.</p></dd><dt><span class="term">
<span class="emphasis"><em>Locking down your phones</em></span>
</span></dt><dd><p>Going out for the night? Don’t want the babysitter tying
up the phone? No problem! A simple tweak to the dialplan, and
the only calls that can be made are to 911, your cell phone, and
the pizza parlor. Any other call attempt will get the recording
“We are paying you to babysit our kids, not make personal
calls.”</p><p>Pretty evil, huh?</p></dd><dt><span class="term">
<span class="emphasis"><em>Controlling the alarm system</em></span>
</span></dt><dd><p>You get a call while on vacation that your Mom wants to
borrow some cooking utensils. She forgot her key and is standing
in front of the house shivering. Piece of cake; a call to your
Asterisk system, a quick digit string into the context you
created for the purpose, and your alarm system is instructed to
disable the alarm for 15 minutes. Mom better get her stuff and
get out quick, though, or the cops’ll be showing up!</p></dd><dt><span class="term">
<span class="emphasis"><em>Managing teenagers’ calls</em></span>
</span></dt><dd><p>How about allocating a specific phone-time limit to your
teenagers? To use the phone, they have to enter their access
codes. They can earn extra minutes by doing chores, scoring all
As, dumping that annoying bum with the bad haircut—you get the
idea. Once they’ve used up their minutes... click... you get
your phone back.</p><p>Incoming calls can be managed as well, via Caller ID.
“Donny, this is Suzy’s father. She is no longer interested in
seeing you, as she has decided to raise her standards a bit.
Also, you should consider getting a haircut.”</p></dd></dl></div></div></div><div class="footnotes"><br /><hr width="100" align="left" /><div class="footnote"><p><sup>[<a id="ftn.asterisk-CHP-15-FN-5" href="#asterisk-CHP-15-FN-5">155</a>] </sup>From the perspective of the closed-source industry, this
attitude is understandable. In his book <span class="emphasis"><em>The Mythical
Man-Month: Essays on Software Engineering</em></span>
(Addison-Wesley), Fred Brooks opined that “the complexity and
communication costs of a project rise with the square of the number
of developers, while work done only rises linearly.” Without a
community-based development methodology, it is very difficult to
deliver products that at best are little more than incremental
improvements over their predecessors, and at worst are merely
collections of patches.</p></div><div class="footnote"><p><sup>[<a id="ftn.asterisk-CHP-15-FN-6" href="#asterisk-CHP-15-FN-6">156</a>] </sup>Eric S. Raymond, <span class="emphasis"><em>The Cathedral and the
Bazaar</em></span>.</p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="asterisk-CHP-15-SECT-2.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="asterisk-CHP-15.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="asterisk-CHP-15-SECT-4.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Paradigm Shift </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> The Future of Asterisk</td></tr></table></div><div xmlns="" id="svn-footer"><hr /><p>You are reading <em>Asterisk: The Future of Telephony</em> (2nd Edition for Asterisk 1.4), by Jim van Meggelen, Jared Smith, and Leif Madsen.<br />
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