Adam Sherman

I was hoping to generate interest with my post about hacking iChat, and it seems that others share my view on the subject:

A.

Now that I’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 important (If you have your priorities straight!), and is the topic of this article.

There are a few possibilities when looking to provide access to emergency services:

• local switch connected to the local PSTN,
• termination provider that supports E911, including location information,
• dedicated POTS phone connected to the local PSTN,
• dedicated local SIP gateway such as a Sipura 3000.

The first solution, which would involve having a single port FXO card in your local PBX assumes that you actually have 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 life critical services, 2 or 3 hours of runtime is probably not enough.

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.

Thirdly is what I term the “Red Handset” 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’s official languages, “Emergency Use Only”, and you’re done. The only downside, as I see it, is that a distressed person may not have the presence of mind to use this phone when they are frantically pounding at the uncaring keys of your fancy IP desk phones.

Last, a very plausible solution comes in the form of an ATA device setup for the purposes of emergency access. For example, the Sipura 3000 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 Sipura 3000 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.

Configuring Polycom SoundPoint IP Phones for Emergency Services Access

In section 4.6.2.1.4.2.2 of the “Administrator Guide for SoundPoint IP SIP”, version 1.3.0, the configuration of emergency services access is described:

1. create a server for your dedicated ATA (4.6.2.1.2)

   <server voIpProt.server.2.address="1.1.1.1" voIpProt.server.2.transport="UDPonly" voIpProt.server.2.register="0" />

2. make sure your local dialplan ensures your locations emergency services access number is immediately dialed (4.6.2.1.4.1)

   <digitmap dialplan.digitmap="911|[2-9]xxxxx|1[2-9]xx[2-9]xxxxxx" />

3. add an emergency entry for the same number (4.6.2.1.4.2.2)

   <dialplan><digitmap dialplan.digitmap="911|[2-9]xxxxx|1[2-9]xx[2-9]xxxxxx" /><routing><emergency dialplan.routing.emergency.1.value="911" dialplan.routing.emergency.1.server.1="2" /></routing></dialplan>

General Fault-Tolerance

You need a few more things to make this a truly fault-tolerant system:

1. have your IP phones on a dedicated switch and make sure you are using Power over Ethernet (PoE),
2. put the above switch on a dedicated UPS,
3. put the ATA on the same dedicated UPS,
4. ensure that this UPS will provide a full-day of runtime with this load,

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.

Contributions to this article from Bill Street.

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’t offer support to anyone not certified by them, more on that later, I relied on VoIP-Info and #asterisk to figure things out. The IP phones are extremely configurable, allowing you to change everything from the sampled sounds they make to very low-level adjustments to the units handling of RTP packets.

The sound quality of the IP500 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 Polycom, that is used in the boardroom.

The look and feel of these units is very professional, much more so than many of the other competing products we looked at. Paul thinks that this is an important aspect when selling to business clients. The units are also well-priced.

Something I am disappointed is the lack of LDAP 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 LDAP tree for this purpose as Cisco does, I believe.

More information on these great IP phones is available on the wiki and at PolycomEmergencyDialplan.