Sizing up VoIP servers

3Com, Avaya, Siemens, and Zultys offer rich telephony features, excellent voice quality, and more or less scalability

See correction at end of review

Voice over IP has reached the point where it's good enough to be taken seriously in the enterprise. The poor voice quality and dropped calls are things of the past, and the current technology delivers features and voice quality as good as, if not better, than what's available with POTS (plain old telephone service) or enterprise digital phone services. In addition, today's IP-based PBXes are reasonably priced, efficient, and flexible. But that doesn't mean they're all alike.

One of the things that struck us as we began testing these products is just how different they are. Two products, from Siemens and Avaya, stem from manufacturers with deep roots in legacy telephone systems. Another, from 3Com, clearly originates from the world of networking and the fourth, from Zultys, began as an IP telephone solution.

Also, while all four of these products are aimed at the enterprise, they target different segments. The 3Com and Zultys products are designed for smaller enterprises, while the gear from Avaya and Siemens are built to handle nearly anything, no matter how big.

What is common among all of these products is that they work on a standard Ethernet network, using standard infrastructure and cabling, but there are some special requirements. Network infrastructure hardware must be VoIP aware so that signaling protocols such as H.323 and SIP can make their way across the network, for example. Likewise, firewalls and other security products must be VoIP aware or calls won't get through.

Further, IP PBX vendors typically advise against deploying their products on your production data network. While it is possible to run your phone and data traffic on the same LAN, it can be very complex to manage the prioritization required to keep voice quality acceptable. Most manufacturers suggest a dedicated network.

We tested the 3Com, Avaya, Siemens, and Zultys IP PBXes at the Advanced Network Computing Laboratory at the University of Hawaii (for details on test procedures, see "How We Tested"). We created a dedicated network of VoIP-aware switches and infrastructure with ties to the public telephone network and the Internet. We conducted performance testing where possible with Spirent Communications' Abacus 5000, and we tested usability and features by making a lot of phone calls to see how they worked.

What we found is that these products are feature-rich. Each provides all the familiar telephony functions, from putting people on hold with insipid music, to transferring calls and recording voice mail. But each has capabilities that go far beyond the basics.

Even better, these PBXes can send phone settings out to the telephone sets attached to the network, providing great control over how the phones work, which features are available to which users, what locations the phones can call, and how the phones can be used. In each case, settings can be changed on the fly.

In most cases, the vendor's IP phones attach to the PBX from outside the network as well as inside. This means that you could take your phone on the road with you, if you were so inclined, and use it from the high-speed Internet connection in your hotel room. While toting a desk phone might not be very practical, software phones, or “softphones,” available for these products accomplish the same thing, as long as you don't mind using your computer to make phone calls while you look at an onscreen picture of a real phone.

All of the phones we tested with these PBXes were provided by the company providing the PBX. All were those big phones you see on executive desks these days. Some even let you surf the Web from your phone, just in case you love your phone more than the computer sitting on the desk next to it. All were reasonably easy to use, given the number of features they had.

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Most importantly, all of the products we tested met the primary goal: providing good telephone service. Voice quality (as measured by Abacus) was high -- possibly better than the POTS phone sitting on your desk. We wouldn't mind using any of these phone systems every day, although in a couple of cases, their beauty was very much in the eye of the beholder.

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3Com VCX V7000

The first thing you notice about the 3Com VCX V7000 is that it looks like it was made by IBM. Granted, the IBM logo on the front of the box has something to do with this impression. IBM only makes the hardware, however, in the form of a 1U Intel-based server running Red Hat Linux. But it's the software, not the hardware, that makes up this PBX.

Because the V7000 stems from the networking world and runs on Linux, it's likely that IT managers will find this product easier to use than products that resemble the PBXes of yore. Most of the management process takes place through well-designed and configurable Web pages. You can add users one at a time, or you can import lists from an external database.

PBXes being what they are, you can only expect so much when it comes to cool interfaces. While 3Com's is Web-based, it still consists of lists of phone numbers and users, pull-down menus, and the like. You won't find any cool drag 'n drop stuff here or elsewhere in PBX land. But, having said that, the 3Com management interfaces work just fine, they're easy to figure out, and they're consistent. You can do a lot worse.

You're not limited to the Web interface on the V7000. As you'd expect, there's a command line interface for hard-core geeks who don't have the patience for GUIs, and there's an X Windows interface available if the Web interface isn't working for some reason.

3Com also provides a Web-based interface for phone users, allowing them to set various parameters for their phones. This means that they can use the Web interface to set up button assignments, forwarding rules, speed dial numbers, and so on. After the settings are entered into the Web form, the V7000 downloads them to the phone almost instantly. Of course, phone administrators can also set up the phone to meet a corporate standard and they can limit the things users can do with their phones.

For users that travel, 3Com provides a softphone application that users can run on their laptops. It presents a detailed image of the 3Com phone on the screen and you can use

it just as you would the phone on your desk. 3Com also supports softphones from X10 and other companies.

The V7000 is a SIP PBX -- you'll need to make sure your firewall is SIP-aware if you plan to contact other PBXes or phones on the other side. Despite SIP's status as a standard, the V7000 has proprietary extensions that kept us from running performance tests using the Abacus tester. We were able to confirm that an earlier version of this PBX, based on Solaris, met all performance requirements.

Avaya S8300 and S8700

Avaya's S8700 is scalable enough to handle nearly any enterprise. Properly configured, this PBX (Avaya calls it a media server) can support up to 36,000 users per server and up to 1 million by networking multiple servers together. The S8300 is much smaller, limited to 450 users per server or 28,800 per network. We tested both PBXes in a networked setting, as though the S8300 were part of a larger enterprise based on the S8700. From an operations standpoint, these boxes are nearly identical, but one important difference is that the smaller S8300 includes integrated voice mail, which is an add-on for the S8700. Both products support the H.323 standard.

The other key difference between these products is that the S8700 is designed to be a high-availability PBX. It includes dual processors and other redundancy features. Because of this, Avaya says that this PBX, normally aimed at the large enterprise market, is also appearing in smaller settings that require high reliability.

In either case, these Avaya PBXes support their users securely. Avaya encrypts both the call setup protocols and the voice stream by default. While this made it difficult to test the Avaya gear (Abacus couldn't understand the encrypted packets) it worked just fine and showed no signs of any operational issues related to the encryption.

What we did notice is the very complete feature set for these products. While some of what we tested is optional, the Avaya PBXes sport features that we didn't find in the competing solutions, such as the ability to extend VoIP connections to cell phones (or any other phone for that matter). This means that it can seamlessly move calls between your IP phone and your cell phone without having to re-establish the call. The S8700 and S8300 also support a six-user conference bridge, so you can make those dreaded, interminable conference calls for less money than if you had to use an external service.

Avaya includes a number of very useful management tools, some of which are optional. You get Avaya's VoIP Monitoring Manager, an easy-to-use graphical tool for managing your phone system, free for 90 days. Then, once you're hooked on it, you have to pay for it. This tool is so intuitive that you're going to buy it; it's worth every nickel of its $5,000 price tag.

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But even if you don't buy the VoIP Monitor, managing the Avaya products isn't particularly difficult. Administrators will encounter either a plain Web-based interface that's mostly text fields and forms, or a command line interface. Either will give you complete control over the operations of the PBX and the phones. You can change button assignments on the fly and the changes show up on the phone immediately.

One nice feature of the management tool is the ability to monitor environmental conditions in the room in which the PBX is installed. That way, you can take steps to cool down the server room before it gets too hot and   the PBX shuts itself down.

Once networked, the Avaya PBXes acted as a single unit. Although we performed this test within the lab at the University of Hawaii, it's clear that you can network these products over far greater distances, preferably using a leased line rather than the open Internet. Avaya says that both the S8300 and the S8700 have the ability to work with virtually any legacy PBX currently in the marketplace, which means that you don't have to replace your phone system to start using VoIP and can instead hook up the Avaya and slowly migrate.

Siemens HiPath 4000

The HiPath 4000 is another mega-PBX that can be configured to support as many as 100,000 users if several of the units are networked together. The individual HiPath 4000 that we tested can support up to 12,000 users. The HiPath 4000 can also be used in conjunction with the smaller HiPath 3000, but we did not test this arrangement. Both models use the H.323 protocol to transmit calls, but they don't support SIP.

The Siemens product is larger than the other PBXes in this test. It's a pedestal design that sits on the floor of your server room rather than in a rack. The larger chassis gives the HiPath 4000 the ability to hold more add-on cards, which means, among other things, that it can support non-IP telephones easily. If you have existing Siemens digital phones, you can still use them with the HiPath and they'll work in the same way the IP phones do.

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Because the HiPath 4000 uses some proprietary extensions to the H.323 standard, we couldn't run most of the Abacus performance tests. However, we were able to test voice quality, which proved to be excellent. The HiPath 4000 supports standard QoS so you can share your voice and data infrastructure, as long as your switches are set to work with standard 802.1p and 802.1Q prioritization. Of course, such operation isn't recommended because voice traffic can be very sensitive to bandwidth restrictions, but it's nice to know you can do it if necessary.

While the Siemens management utilities aren't the sexiest on the planet, they are perhaps the best documented. Help files and tutorials abound, they're easy to access, and they're complete. You can interact with the HiPath in German, as you'd expect, and also in English. In a recent improvement, even the command line interface now works in English. One quibble: Some pop-up messages still appear in German.

You set up the HiPath 4000 by following a well-designed wizard that leads you through the steps. The management interface consists of a straightforward Web-based GUI; you select options from lists and drop-down menus. Help is available everywhere and you get confirmation boxes where necessary. Training IT staff to manage the HiPath should be a piece of cake.

You are limited to using Siemens telephones with the HiPath, a limitation some may not like. But you can use either IP phones or standard digital phones. If you already have a Siemens PBX, this can make upgrading a lot less intrusive. Through the management tools, you can designate who is authorized to make changes to the phones.

One nice feature is a backup utility that supports a magneto-optical disk. If something bad happens to your PBX, at least you won't have to start again from scratch. In addition, you can network the HiPath 4000 to other Siemens units for redundancy. Likewise, the HiPath 4000 itself can carry redundant processors and power supplies for those mission-critical applications (aren't nearly all phone systems mission critical?). Networked HiPaths can be administered centrally.

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