Open source PBXes: free flexibility

Capable IP PBXes from Pingtel, Digium are free for the downloading, but require admin expertise to use effectively

One great thing about the open source movement is that if there’s a feature of any kind that someone somewhere needs, it will be made available for everyone. As a result, the open source PBXes tested here are feature-filled Swiss Army knives of communications solutions.

Like other open source products, these PBXes don’t necessarily cost anything to obtain. That doesn’t mean, however, there aren’t costs involved with getting these phone systems running. Phone hardware is still required, and the expertise to turn the software into something you can use in your enterprise doesn’t come cheap. Open source product support comes from the community itself, so you’ll need to know where to look and who to ask to get what you need.

If that doesn’t work for your company, both Pingtel and Digium will provide support and services for a reasonable cost. If you’re willing to invest some time and thought in picking the right product, getting the right plug-ins and options, and training someone on your staff to manage the PBX, you can save a lot of money and very likely get a solution that exactly fits your needs.

Asterisk V1.0.3

Digium calls Asterisk the first open source PBX. In reality, it’s a lot more than a PBX: It also takes on the functions of a media server, a protocol gateway, and a conference bridge. It goes beyond VoIP, too, supporting other types of digital communications and even POTS systems.

Asterisk can be installed on anything that will run Linux with kernel Version 2.4 or later. It will also run on FreeBSD Unix and on Mac OS X, and another version will run on coLinux under Microsoft Windows, although its functionality is limited.

As you’d expect for a product that supports such a wide variety of hardware, you can add a lot to the Asterisk system in terms of infrastructure and software. Because it’s open source, there’s also a wealth of applications that add functions to Asterisk, such as support for a variety of phone interfaces or concentrators and media gateway services such as outboard conferencing.

You’ll probably need to add at least some of those functions. Although Asterisk is fully functional when you download it, the base product doesn’t include many of the interfaces and capabilities — such as graphical management interfaces — available from third parties.

This observation is not to suggest that Asterisk is missing features — far from it. Most of the features are present in basic form, so you’ll be making management changes, adds, moves, and the like by editing a text file. As long as you can use a Linux text editor, follow some basic instructions, and deal with a set of configuration files that are reasonably intuitive, there’s little else you’ll need.

Although management via text-file editing is far from sexy, it is effective, fast, and reduces mouse-related carpal tunnel exposure. Dealing directly with configuration files, though, requires more admin expertise than using a GUI, and that may limit Asterisk’s usefulness at some companies.

For the test, the Digium engineers and I created a somewhat atypical phone network. It included a series of SIP-based phones, along with analog phones, MGCP (Media Gateway Control Protocol) and H.323 phones, SCCP (Signaling Connection Control Part) phones, and phones using several other digital protocols.

We installed the PBX software on a pair of mismatched, low-end Pentium desktop computers, each equipped with Ethernet adapters and a four-way T1 adapter. Two of the T1 lines linked the PBXes; two of the other T1 lines from one of the PBXes went to the analog phones.

The low-end desktop PCs were used to test Digium’s claim that you don’t need anything special to bring up its PBX. In reality, you’d be out of your mind to do this, because phone service is critical for most companies. Your phone system should be installed on some nicely redundant, server-quality platforms. The Asterisk installation proved its point, though — it requires no fancy hardware.

With this setup, I could call any phone on the network from any other phone. Call quality remained good, and all PBX features (including standards such as automatic call distribution, voice mail services, and call queuing) were available. Some features were phone-dependent — you won’t suddenly get advanced calling features on plain analog phones — but the basics were there for every phone.

Asterisk worked fine, but consider the amount of open source familiarity necessary to reach its full potential and integrate all the pieces you might want in an enterprise deployment. There are plenty of options to add more bells, whistles, and interfaces, but you’ll need to know what you’re doing in order to implement them.

SIPxchange V.2.4

Unlike Asterisk’s purely open source approach, Pingtel’s SIPxchange has a more commercial flavor. It’s still an open source product — the base PBX, sipX, can be downloaded from the SIPfoundry Web site for free — but if you pay Pingtel’s modest price, you get additional support, plus plug-ins and tools such as media gateway services.

Most companies will opt for a dual-processor platform with power and disk redundancy for their IP PBX, but even here, the cost of moving to SIPxchange is very low compared to other commercial competitors we reviewed.

Pingtel’s distribution of SIPxchange runs on Red Hat Linux and is compatible with most commercially available SIP-based IP phones. The 2.4 distribution includes Web-based graphical management interfaces, an automated attendant, and voice mail, among other features.

I tested the Pingtel software on a 1U server provided by the company. Most of the phones we used were Cisco 7912, 7940, and 7960 SIP, but we also included Pingtel’s sipX softphone, which could be useful for traveling employees. All phones were connected to an Ethernet switch on a dedicated, closed network.

Initial installation of the sipX and Pingtel software required a considerable amount of manual intervention. Luckily, after the software was installed, the graphical interfaces eased the configuration burden, and there are scripts for many tasks.

However, adding phones to the network isn’t always easy. You have to enter each phone’s MAC (media access control) address individually before you can use the phone. This means either typing that address in or using a bar-code scanner, because the Pingtel software has no way to query the phones for this information. Plus, you’ll have to repeat this process each time you add a new phone to the network. Unless you have a very small phone network, this could rapidly become a burden on the IT staff.

On the other hand, once you add the phones, managing them is made easier by a well-designed interface that allows you to control the phones’ features and functions. You can, for example, assign specific functions to specific buttons on the phones cen-trally, and Pingtel includes graphical interfaces for user inboxes and for control of voice mail.

After the initial setup, I found SIPxchange to be very effective and easy to use. The user interfaces are convenient, and the graphical management interfaces are well-designed and intuitive, so you won’t have to hire multiple sipX experts to run your phone system (although you will still need at least one). This is a solution that should fit in well with your enterprise, especially if you have experience with commercial distributions of open source software.

Ringing Up Open Source

Basic call services, such as voice mail, transfer, and call waiting, can all be done with any phone supported by these products. Advanced features, such as outboard conferencing, depend on what the administrator wants to allow, and, of course, what the phone will support.

Both of these phone systems seem to have a nearly limitless ability to be expanded and customized, no matter what it is you wish to accomplish. That’s the beauty of open source software, and it certainly holds true with PBXes.

Asterisk, of course, is just that — open source. It runs on a variety of platforms and supports several types of digital communications. Although it includes fewer management features as standard equipment, similar features are available from the open source community. Adding them, or almost anything else, is reasonably easy to accomplish if you’re familiar with the workings of open source technology.

With Pingtel’s version of sipX, you get more but you also pay more. It’s easier to manage, thanks to the included graphical interfaces, so you’ll need to spend less time training staff. If you’re looking for just a PBX, then Pingtel is well worth the modest cost. If you’re looking for something more, you’re going to need to look to the open source community and add it yourself — and it will only cost you a bit of time and installation effort.

InfoWorld Scorecard
Implementation (10.0%)
Scalability (20.0%)
Management (30.0%)
Features (30.0%)
Value (10.0%)
Overall Score (100%)
Digium Asterisk V1.0.3 6.0 8.0 7.0 8.0 7.0 7.4
Pingtel SIPxchange v. 2.4 7.0 8.0 8.0 8.0 8.0 7.9

Copyright © 2005 IDG Communications, Inc.

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