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<channel>
	<title>Adam Sherman &#187; VoIP</title>
	<atom:link href="http://www.sherman.ca/archives/category/voip/feed/" rel="self" type="application/rss+xml" />
	<link>http://www.sherman.ca</link>
	<description>Mostly random thoughts on software, gear and the great outdoors.</description>
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		<title>iChat AV Updates</title>
		<link>http://www.sherman.ca/archives/2005/04/04/ichat-av-updates/</link>
		<comments>http://www.sherman.ca/archives/2005/04/04/ichat-av-updates/#comments</comments>
		<pubDate>Mon, 04 Apr 2005 12:24:13 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2005/04/04/ichat-av-updates/</guid>
		<description><![CDATA[I landed on Irwin Lazar&#8217;s blog, from a post on VoIP Watch, mentioning the updates to iChat AV coming in Mac OS X Tiger (10.4). All very interesting features, but I really want Apple to support generic SIP-based services. (As I&#8217;ve mentioned before.) I think Apple is in a unique position to be able to [...]]]></description>
			<content:encoded><![CDATA[<p>I landed on <a href="http://www.irwinlazar.com/">Irwin Lazar&#8217;s</a> blog, from a <a href="http://andyabramson.blogs.com/voipwatch/2005/04/mac_video_via_i.html">post</a> on VoIP Watch, <a href="http://www.irwinlazar.com/realtime/2005/03/apple_tiger_ich.html" title="Irwin Lazar's &quot;Real-Time&quot; Blog: Apple Tiger: iChat AV Updates">mentioning</a> the updates to iChat AV coming in Mac OS X Tiger (10.4). All very interesting features, but I really want Apple to support generic SIP-based services. (As I&#8217;ve <a href="http://www.sherman.ca/archives/2004/08/28/hacking-ichat-for-generic-sip-support/">mentioned</a> before.)</p>

<p>I think Apple is in a unique position to be able to make their platform the premier integrated communications and presence environment. Hey Steve, you listening?</p>

<p>A.</p>
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		<item>
		<title>Skype</title>
		<link>http://www.sherman.ca/archives/2005/02/21/skype/</link>
		<comments>http://www.sherman.ca/archives/2005/02/21/skype/#comments</comments>
		<pubDate>Mon, 21 Feb 2005 05:47:36 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2005/02/21/skype/</guid>
		<description><![CDATA[In a previous post, I discussed the important of integrated VoIP, IM and presence. Andy Abramson writes: [Adam Sherman] misses one key player in the presence space. Skype. It may be justified as he describes the benefits of IM, VoIP and Presence using SIP and SIMPLE, two elements that SKYPE lacks. I guess I better come [...]]]></description>
			<content:encoded><![CDATA[<p>In a <a href="http://www.sherman.ca/archives/2004/10/21/voip-and-presence/">previous post</a>, I discussed the important of integrated VoIP, IM and presence.</p>

<p><a href="http://andyabramson.blogs.com/voipwatch/">Andy Abramson</a> <a href="http://andyabramson.blogs.com/voipwatch/2005/02/adam_sherman_on.html">writes</a>:</p>

<blockquote>
  <p>[Adam Sherman] misses one key player in the presence space. Skype. It may be justified as he describes the benefits of IM, VoIP and Presence using SIP and SIMPLE, two elements that SKYPE lacks.</p>
</blockquote>

<p>I guess I better come out and say it: <em><a href="http://www.skype.com/">Skype</a> scares me</em>. There.</p>

<p><a href="http://www.skype.com/">Skype</a> has a solid product, backed by a solid service and is giving it away for free. They intend to charge for value-added services like calling the PSTN. The client works through all kinds of weird network configurations as is fully cross-platform. It has most (all?) of the requisite presence functionality.</p>

<p>So why am I scared? Two reasons: <em>central control</em> and <em>standards</em>.</p>

<p>If <a href="http://www.skype.com/">Skype</a> takes off and corners a piece of the market, users will be dependent on a central, <em>proprietary</em>, system. As I mentioned previously, I believe that this is a critical flaw and that we must adopt standards that are distributed in nature. The proof of this is in SMTP, which is extremely reliable and needs no central authority (Other than the root DNS system.) Which brings me to my second concern&#8230;</p>

<p><a href="http://www.skype.com/">Skype</a> uses no standards. Admittedly, this is probably a major reason for its success. While SIP struggles to become a fully functional protocol by extending with SIMPLE, we deal with poor audio codecs and terrible user agent implementations. <a href="http://www.skype.com/">Skype</a> doesn&#8217;t have to worry about this. But these protocols will mature and implementations will be tuned. We will then, hopefully, live in a wonderfully interconnected world where the limitations of the long-forgotten public switched telephone network will be a thing of the past.</p>

<p>Until then though, I hope <a href="http://www.skype.com/">Skype</a> does well enough to raise the profile of VoIP but not so well that it gets us into a technological dead-end.</p>

<p>Cheers.</p>

<p><strong>Update:</strong> I think that <a href="http://www.xten.com">XTen</a> understands where future communications should look like. Erik Lagerway <a href="http://sipthat.com/archives/000210.html">posted</a> about the IETF going into P2P VoIP land. I really want to try out eyeBeam!</p>
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		</item>
		<item>
		<title>A passable VoIP emergency solution</title>
		<link>http://www.sherman.ca/archives/2004/10/31/a-passable-voip-emergency-solution/</link>
		<comments>http://www.sherman.ca/archives/2004/10/31/a-passable-voip-emergency-solution/#comments</comments>
		<pubDate>Sun, 31 Oct 2004 13:45:20 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[Mobile]]></category>
		<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2004/10/31/a-passable-voip-emergency-solution/</guid>
		<description><![CDATA[This has some serious merit. If the SIP registrar can notice when an endpoint&#8217;s IP address changes and proactively query the user to reset the emergency services destination, we could have a workable solution.]]></description>
			<content:encoded><![CDATA[<p><a href="http://andyabramson.blogs.com/voipwatch/2004/10/more_e911_ideas.html">This</a> has some serious merit. If the SIP registrar can notice when an endpoint&#8217;s IP address changes and proactively query the user to reset the emergency services destination, we could have a workable solution.</p>
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		<item>
		<title>VoIP and Presence</title>
		<link>http://www.sherman.ca/archives/2004/10/21/voip-and-presence/</link>
		<comments>http://www.sherman.ca/archives/2004/10/21/voip-and-presence/#comments</comments>
		<pubDate>Thu, 21 Oct 2004 19:57:12 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[Networking]]></category>
		<category><![CDATA[Software]]></category>
		<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2004/10/21/voip-and-presence/</guid>
		<description><![CDATA[Corporate and personal communications is undergoing an obvious revolution right before our eyes. I won&#8217;t comment on this aspect of VoIP since there are so many doing so, particularly in the large news publications. However, we&#8217;re missing something: presence. Instant messaging has boomed and become an almost integral part of our society, with youth leading [...]]]></description>
			<content:encoded><![CDATA[<p>Corporate and personal communications is undergoing an obvious revolution right before our eyes. I won&#8217;t comment on this aspect of VoIP since there are so many doing so, particularly in the large news publications. However, we&#8217;re missing something: <em>presence</em>.</p>

<p><a href="http://en.wikipedia.org/wiki/Instant_messenger">Instant messaging</a> has boomed and become an almost integral part of our society, with youth leading this integration. Have we not noticed that this form of communication is almost entirely controlled by a select few corporations? To name a few:</p>

<ul>
<li><a href="http://www.aol.com">AOL</a> (AIM &#38; ICQ)</li>
<li><a href="http://www.msn.com">Microsoft</a> (MSN)</li>
<li><a href="http://www.yahoo.com">Yahoo</a></li>
</ul>

<p>This is all a <em>Bad Thing&trade;</em>! Lets reminisce for a moment about good, old fashioned, email service. This technology is completely decentralized and relies on each entity having their own SMTP system. If I want to send you mail, I simply do a DNS lookup to find your mail server and off I go. This server can either be provided by your ISP, out-sourced to another provider or you may have set it up internally.</p>

<p>Contrast this with IM, where your messages are being routed by a third-party who:</p>

<ul>
<li>Is not receiving money from you</li>
<li>Made you accept a disclaimer that basically guarantees less than nothing</li>
<li>Doesn&#8217;t really want to interface with the other IM providers</li>
</ul>

<p>To actually start discussing VoIP now, the above <em>prevents good presence for VoIP applications</em>.</p>

<p>Thankfully, the defacto VoIP protocol, <a href="http://www.softarmor.com/sipwg/">SIP</a>, has full support for an SMTP-like distrbuted model using <a href="http://www.voip-info.org/wiki-DNS+SRV">SRV</a> records in DNS. This allows the DNS system to be queries for the correct <a href="http://www.softarmor.com/sipwg/">SIP</a> server for a domain and therefore gives us nice, convenient addresses for voice communications using the familiar &#8220;user@domain&#8221; form.</p>

<p>Built on top of <a href="http://www.softarmor.com/sipwg/">SIP</a>, there is <a href="http://www.softarmor.com/simple/">SIMPLE</a> or the S I M P L E. This upgrades your SIP infrastructure to support full presence and <a href="http://en.wikipedia.org/wiki/Instant_messenger">instant messaging</a> capabilities. So far, I know of very few clients that have full SIMPLE support:</p>

<ul>
<li><a href="http://www.xten.com/">X-Ten</a>&#8216;s <a href="http://www.xten.com/index.php?menu=products&#38;smenu=eyebeam">eyeBeam</a> (Commercial, Win32 &#38; Mac OS X)</li>
<li><a href="http://www.pulver.com">Pulver</a>&#8216;s <a href="http://www.pulver.com/communicator/">pulver.Communicator</a> (Win32)</li>
</ul>

<p>Also, I believe that <a href="http://www.microsoft.com">Microsoft</a>&#8216;s Windows Messenger is available in a <a href="http://www.softarmor.com/sipwg/">SIP</a> edition.</p>

<p>A major open instant messaging protocol, <a href="http://www.jabber.org/">Jabber</a>, also has the above mentioned <a href="http://www.voip-info.org/wiki-DNS+SRV">SRV</a> capability. It seems to be under implemented in practice, however, with many people not even bothering. <a href="http://www.jabber.org/">Jabber</a> uses the <a href="http://www.xmpp.org/">XMPP</a> protocol and bridges exist to allow <a href="http://www.softarmor.com/simple/">SIMPLE</a> to interoperate with it.</p>

<p>I&#8217;m rambling here. To get to the point, it seems that integrating <a href="http://www.softarmor.com/sipwg/">SIP</a> hardware devices : Analog Telephone Adapters (ATAs), like those from <a href="http://www.sipura.com/">Sipura</a>, and desk phones like those from <a href="http://www.polycom.com">Polycom</a>; with presence provided either by <a href="http://www.softarmor.com/simple/">SIMPLE</a> or <a href="http://www.xmpp.org/">XMPP</a>, <em>is a problem</em>. See, when you are using a great hardware phone for actual calling, you can&#8217;t do decent presence. How will my <a href="http://www.jabber.org/">Jabber</a> client know that I&#8217;m on the phone in order to set my status to &#8220;On the phone&#8221;?</p>

<p>My conclusion is that we should really be using softphones. Why not? Don&#8217;t we all have laptops and <a href="http://www.bluetooth.com/">Bluetooth</a> headsets? <img src='http://www.sherman.ca/wp-includes/images/smilies/icon_smile.gif' alt=':-)' class='wp-smiley' />  Well, I intend to get myself fully setup this way. To heck with all the other ways of getting voice service. Also, <a href="http://www.jabber.org/">Jabber</a> isn&#8217;t a great candidate unless you use something like the <a href="http://www.myjabber.net/">myJabber</a> Instant Messaging Client for XMPP and myJabber AE Soft Phone combination, which is non-standard.</p>

<p>More to come on this topic once I get a copy of <a href="http://www.xten.com/index.php?menu=products&#38;smenu=eyebeam">eyeBeam</a> for Mac OS X to play with.</p>
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		<item>
		<title>Sipura Volume</title>
		<link>http://www.sherman.ca/archives/2004/10/19/sipura-volume/</link>
		<comments>http://www.sherman.ca/archives/2004/10/19/sipura-volume/#comments</comments>
		<pubDate>Tue, 19 Oct 2004 17:59:06 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2004/10/19/sipura-volume/</guid>
		<description><![CDATA[We had been noticing that incoming calls over the FXO port of our Sipura 3000 (SPA-3000) were a little too soft. Obviously, turning the volume up on our Polycom phones helped but I thought this should be adjustable using on of the SPA-3000s zillion options. From the user guide, I determined that &#8220;PSTN to SPA [...]]]></description>
			<content:encoded><![CDATA[<p>We had been noticing that incoming calls over the FXO port of our <a href="http://www.sipura.com/products/spa3000.htm">Sipura 3000</a> (<a href="http://www.sipura.com/products/spa3000.htm">SPA-3000</a>) were a little too soft. Obviously, turning the volume up on our Polycom phones helped but I thought this should be adjustable using on of the SPA-3000s zillion options.</p>

<p>From the <a href="http://www.sipura.com/Documents/SipuraSPAUserGuidev2.0.9.pdf">user guide</a>, I determined that &#8220;PSTN to SPA Gain&#8221;, on the PSTN Line tab, allows the gain to be adjusted from -15dB to 12dB. I set it to 1, and am very happy with the volume.</p>
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		<title>Aswath Rao on Apple and VoIP</title>
		<link>http://www.sherman.ca/archives/2004/09/30/aswath-rao-on-apple-and-voip/</link>
		<comments>http://www.sherman.ca/archives/2004/09/30/aswath-rao-on-apple-and-voip/#comments</comments>
		<pubDate>Thu, 30 Sep 2004 17:45:48 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[Software]]></category>
		<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2004/09/30/aswath-rao-on-apple-and-voip/</guid>
		<description><![CDATA[I was hoping to generate interest with my post about hacking iChat, and it seems that others share my view on the subject: A.]]></description>
			<content:encoded><![CDATA[<p>I was hoping to generate interest with my <a href="http://www.sherman.ca/archives/2004/08/28/hacking-ichat-for-generic-sip-support/">post</a> about hacking iChat, and it seems that <a href="http://www.gigaom.com/2004/09/open_letter_to_s.php">others</a> share my view on the subject:</p>

<p>A.</p>
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		<item>
		<title>Polycom Emergency Dialplan Setup</title>
		<link>http://www.sherman.ca/archives/2004/09/04/polycomemergencydialplan/</link>
		<comments>http://www.sherman.ca/archives/2004/09/04/polycomemergencydialplan/#comments</comments>
		<pubDate>Sat, 04 Sep 2004 14:28:14 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2004/09/04/polycomemergencydialplan/</guid>
		<description><![CDATA[Now that I&#8217;ve setup Polycoms SoundPoint IP500 phone system to talk to a local Asterisk system and everything is working as expected, the next step is to think of fault-tolerance. In my mind, a VoIP system has two distinct responsibilities regarding reliability: to provide business critical and life critical services. Obviously, the latter is more [...]]]></description>
			<content:encoded><![CDATA[<p>Now that I&#8217;ve setup Polycoms <a href="http://www.sherman.ca/archives/2004/09/02/soundpointip/">SoundPoint IP500</a> phone system to talk to a local Asterisk system and everything is working as expected, the next step is to think of fault-tolerance. In my mind, a VoIP system has two distinct responsibilities regarding reliability: to provide <em>business critical</em> and <em>life critical</em> services. Obviously, the latter is more important (If you have your priorities straight!), and is the topic of this article.</p>

<p>There are a few possibilities when looking to provide access to emergency services:</p>

<ul>
<li>local switch connected to the local PSTN,</li>
<li>termination provider that supports E911, including location information,</li>
<li>dedicated POTS phone connected to the local PSTN,</li>
<li>dedicated local SIP gateway such as a <a href="http://www.sipura.com/products/spa3000.htm">Sipura 3000</a>.</li>
</ul>

<p>The first solution, which would involve having a single port FXO card in your local PBX assumes that you actually <em>have</em> a local PBX which is not always the case. It also adds complexity to your infrastructure, which then must provide backup power to another server. Remember, when talking about <em>life critical</em> services, 2 or 3 hours of runtime is probably not enough.</p>

<p>The second solution appears very promising since it removes the burden of local systems however, since you must still provide power to the VoIP terminals themselves, you are not much farther ahead. In addition, the reliability of your connection to your provider must now be reexamined, something that is often very costly. Finally, since the majority of VoIP termination providers do not yet offer 911 access, this is a mout point.</p>

<p>Thirdly is what I term the <em>&#8220;Red Handset&#8221;</em> approach. A very simple and reliable solution: go out and buy the the most brightly colored POTS phone you can find, mount it on a prominent location, and connect it directly to the local PSTN. Label it, in your country&#8217;s official languages, <em>&#8220;Emergency Use Only&#8221;</em>, and you&#8217;re done. The only downside, as I see it, is that a distressed person may not have the presence of mind to use <em>this</em> phone when they are frantically pounding at the uncaring keys of your fancy IP desk phones.</p>

<p>Last, a very plausible solution comes in the form of an ATA device setup for the purposes of emergency access. For example, the <a href="http://www.sipura.com/products/spa3000.htm">Sipura 3000</a> has both an FXS and an FXO port; this allows you to use it simultaneously as an adapter for analog devices, such as that rather expensive conference room unit you bought during The Boom, and as a gateway to the local PSTN. You could, and probably should, implement solution three by connecting a handset to the ATAs FXS port since the <a href="http://www.sipura.com/products/spa3000.htm">Sipura 3000</a> has a relay that connects the FXS device to the FXO line in the event of power failure. Program the Sipura for open, unauthenticated access and then configure your IP phones to use it for emergency access.</p>

<h4>Configuring Polycom SoundPoint IP Phones for Emergency Services Access</h4>

<p>In section <code>4.6.2.1.4.2.2</code> of the &#8220;Administrator Guide for SoundPoint IP SIP&#8221;, version <code>1.3.0</code>, the configuration of emergency services access is described:</p>

<ol>
<li><p>create a server for your dedicated ATA (<code>4.6.2.1.2</code>)</p>

<p><code>&lt;server   voIpProt.server.2.address="1.1.1.1"
    voIpProt.server.2.transport="UDPonly"
    voIpProt.server.2.register="0" /&gt;</code></p></li>
<li><p>make sure your local dialplan ensures your locations emergency services access number is immediately dialed (<code>4.6.2.1.4.1</code>)</p>

<p><code>&lt;digitmap dialplan.digitmap="911|[2-9]xxxxx|1[2-9]xx[2-9]xxxxxx" /&gt;</code></p></li>
<li><p>add an emergency entry for the same number (<code>4.6.2.1.4.2.2</code>)</p>

<p><code>&lt;dialplan&gt;&lt;digitmap   dialplan.digitmap="911|[2-9]xxxxx|1[2-9]xx[2-9]xxxxxx" /&gt;&lt;routing&gt;&lt;emergency    dialplan.routing.emergency.1.value="911"
                dialplan.routing.emergency.1.server.1="2" /&gt;&lt;/routing&gt;&lt;/dialplan&gt;</code></p></li>
</ol>

<h4>General Fault-Tolerance</h4>

<p>You need a few more things to make this a truly fault-tolerant system:</p>

<ol>
<li>have your IP phones on a dedicated switch and make sure you are using <em>Power over Ethernet</em> (PoE),</li>
<li>put the above switch on a dedicated UPS,</li>
<li>put the ATA on the same dedicated UPS,</li>
<li>ensure that this UPS will provide a full-day of runtime with this load,</li>
</ol>

<p>One more, not so obvious, issue: check with your local PSTN access provider to verify that your lines will function during a power outage. Many business lines are actually digital and have local equipment that requires power. Usually, battery backup is installed but often is not sufficient. This would be an issue whether or not you are using VoIP.</p>

<p><em>Contributions to this article from Bill Street.</em></p>
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		<title>SoundPointIP</title>
		<link>http://www.sherman.ca/archives/2004/09/02/soundpointip/</link>
		<comments>http://www.sherman.ca/archives/2004/09/02/soundpointip/#comments</comments>
		<pubDate>Thu, 02 Sep 2004 12:57:15 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[Gear]]></category>
		<category><![CDATA[Networking]]></category>
		<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2004/09/02/soundpointip/</guid>
		<description><![CDATA[The Polycom SoundPoint IP are a line of very nice VoIP phones for business use. The current model line-up includes: SoundPoint IP300 SoundPoint IP500 SoundPoint IP600 SoundStation IP I setup five IP500s last week and hooked them up to an Asterisk system. Since Polycom doesn&#8217;t offer support to anyone not certified by them, more on [...]]]></description>
			<content:encoded><![CDATA[<p>The <a href="http://www.polycom.com/">Polycom</a> <a href="http://www.polycom.com/products_services/1,1443,pw-34-182,00.html">SoundPoint IP</a> are a line of very nice VoIP phones for business use. The current model line-up includes:</p>

<ul>
<li><a href="http://www.polycom.com/">SoundPoint IP300</a></li>
<li><a href="http://www.polycom.com/">SoundPoint IP500</a></li>
<li><a href="http://www.polycom.com/">SoundPoint IP600</a></li>
<li><a href="http://www.polycom.com/">SoundStation IP</a></li>
</ul>

<p>I setup five <a href="http://www.polycom.com/">IP500s</a> last week and hooked them up to an <a href="http://www.voip-info.org/wiki-Asterisk">Asterisk</a> system. Since <a href="http://www.polycom.com/">Polycom</a> doesn&#8217;t offer support to anyone not certified by them, more on that later, I relied on <a href="http://www.voip-info.org">VoIP-Info</a> and <a href="http://www.freenode.net">#asterisk</a> to figure things out. The IP phones are <em>extremely</em> configurable, allowing you to change everything from the sampled sounds they make to very low-level adjustments to the units handling of <a href="http://www.voip-info.org/wiki-RTP">RTP</a> packets.</p>

<p><img class="thumbnail" src="http://www.sherman.ca/content/polycom_soundpoint_ip500-tm.jpg" height="100" width="141" align="left" border="0" hspace="0" vspace="0"/>The sound quality of the <a href="http://www.polycom.com/">IP500</a> units that we have is terrific.  The built-in full duplex speakerphone is also very good, though not quite as perfect as the purpose built conference phone, also from <a href="http://www.polycom.com/">Polycom</a>, that is used in the boardroom.</p>

<p>The look and feel of these units is very professional, much more so than many of the other competing products we looked at. <a href="http://success.typepad.com/smallbizwiz/">Paul</a> thinks that this is an important aspect when selling to business clients. The units are also well-priced.</p>

<p>Something I am disappointed is the lack of <a href="http://www.openldap.org/">LDAP</a> directory support. While the phones have the ability to load an XML formatted directory from their boot server, they will not periodically update from it. It would be far more integrated to simply use an <a href="http://www.openldap.org/">LDAP</a> tree for this purpose as <a href="http://www.cisco.com/en/US/products/hw/phones/ps379/index.html">Cisco</a> does, I believe.</p>

<p>More information on these great IP phones is available on the <a href="http://www.voip-info.org/wiki-Polycom%20Phones">wiki</a> and at PolycomEmergencyDialplan.</p>
]]></content:encoded>
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		<item>
		<title>AsteriskiChat</title>
		<link>http://www.sherman.ca/archives/2004/08/29/asteriskichat/</link>
		<comments>http://www.sherman.ca/archives/2004/08/29/asteriskichat/#comments</comments>
		<pubDate>Sun, 29 Aug 2004 18:16:50 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2004/08/29/asteriskichat/</guid>
		<description><![CDATA[I will eventually keep a cross-reference of related content here.]]></description>
			<content:encoded><![CDATA[<p>I will eventually keep a cross-reference of related content here.</p>
]]></content:encoded>
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		<slash:comments>0</slash:comments>
		</item>
		<item>
		<title>Hacking iChat for Generic SIP Support</title>
		<link>http://www.sherman.ca/archives/2004/08/28/hacking-ichat-for-generic-sip-support/</link>
		<comments>http://www.sherman.ca/archives/2004/08/28/hacking-ichat-for-generic-sip-support/#comments</comments>
		<pubDate>Sun, 29 Aug 2004 03:43:35 +0000</pubDate>
		<dc:creator>adam</dc:creator>
				<category><![CDATA[Software]]></category>
		<category><![CDATA[VoIP]]></category>

		<guid isPermaLink="false">http://www.sherman.ca/2004/08/28/hacking-ichat-for-generic-sip-support/</guid>
		<description><![CDATA[The Setting At this week&#8217;s OJUG meeting, I mentioned to Patrick Linskey that I would really like to see iChat as a client to generic SIP servers. He said that it may be possible given Cocoa&#8217;s design, so I&#8217;ve been looking into it. Here is a set of related links: Apple iChat Technology Brief, Blog [...]]]></description>
			<content:encoded><![CDATA[<h4>The Setting</h4>

<p>At this week&#8217;s <a href="http://www.sherman.ca/archives/2004/08/28/ojug-on-august-26th-2004/">OJUG</a> meeting, I mentioned to <a href="http://jroller.com/page/pcl">Patrick Linskey</a> that I would <strong>really</strong> like to see <a href="http://www.apple.com/ichat/">iChat</a> as a client to generic <a href="http://www.voip-info.org/wiki-SIP" title="Session Initiation Protocol">SIP</a> servers. He said that it may be possible given Cocoa&#8217;s design, so I&#8217;ve been looking into it. Here is a set of related links:</p>

<ol>
<li><a href="http://images.apple.com/ichat/pdf/ChatAV_TB_02052004.pdf" title="Technology Brief, Mac OS X:iChat AV">Apple iChat Technology Brief</a>,</li>
<li><a href="http://zeitblog.zeitgeist.com/archives/000084.html" title="Apple Rocks even more!">Blog entry on the subject, gives some protocol details</a></li>
<li><a href="http://tim.geekheim.de/archive/000145.html" title="Troubleshooting iChat AV">Another entry discussing the protocols</a></li>
</ol>

<p>I also took a look around to see what iChat is doing under the covers. First, when iChat is running, it uses 2 pieces:</p>

<ul>
<li><code>/Applications/iChat.app/Contents/MacOS/iChat</code></li>
<li><code>/System/Library/PrivateFrameworks/InstantMessage.framework
/iChatAgent.app/Contents/MacOS/iChatAgent</code></li>
</ul>

<p>When you are doing audio or video communications, you will notice access another shared library:</p>

<ul>
<li><code>/System/Library/PrivateFrameworks/VideoConference.framework</code></li>
</ul>

<p>The above is where it gets interesting. I ran <a href="http://www.codethecode.com/Projects/class-dump/" title="This is a command-line utility for examining the Objective-C  segment of Mach-O files. It generates declarations for the classes, categories and protocols. This is the same information  provided by using 'otool -ov', but presented as normal Objective-C declarations.">class-dump</a> on it, output available <a href="http://www.sherman.ca/content/VideoConferenceFrameworkDump.txt">here</a>. Of particular interest is an interface called <code>SIPManager</code>. There is also a lot of <a href="http://www.voip-info.org/wiki-RTP" title="Real-time Transport Protocol">RTP</a> and <a href="http://www.voip-info.org/wiki-SDP" title="Session Description Protocol">SDP</a> related things in there, but I&#8217;m now over my head in regards to grokking Objective-C.</p>

<h4>Where Do We Go From Here?</h4>

<p>I believe it is very important to have a general <a href="http://www.voip-info.org/wiki-SIP" title="Session Initiation Protocol">SIP</a> client that has iChat&#8217;s audio quality and integration into the operating system. Can we hack it?</p>
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