How to choose VoIP for SMBs - Part Two

Richard Chirgwin continues his advisory series on selecting SME VoIP with a look at how to choose an in-house VoIP system.

Last week, we looked at choosing a broadband service that can support SME VoIP requirements. The next question for the prospective VoIP user is how to select a suitable in-house VoIP system.

The first question for the SME is how much time and effort you can devote to setting up a VoIP system.

The advantage of having a system installed by a professional integrator is straightforward: you completely don't have to learn how the system operates to get it up and running. The downside is that the consultant's time is going to cost money.

You'll save some of that time and money if you have a clear idea of the "must haves" of your VoIP setup. Build a checklist - and make sure it includes everything you want the phone system to do. A few items that you can't overlook:

  • How many extensions will you have?
  • How many direct indial numbers will you have?
  • How do you want the system to handle voicemail?
  • Which extensions should ring for incoming calls?
  • Do you want number-dependent rings? For example, should a call to the reception number behave differently to a call to someone's extension?
  • Will you be using auto-attendant during office hours, or only when the office is closed?
  • What is your office-hours schedule? (Don't forget to include public holidays)
  • What are your outbound call rules? (For example, will you be restricting calls such as international destinations and premium numbers?)
  • You'll need a checklist like this regardless of who is setting up your system - and you should keep it copied and backed up, in case anything goes wrong.

Complexity Versus Cost

Probably the cheapest way to set up an office VoIP system is to set up a business-class server with a copy of the open-source Asterisk telephony server ( The software is free - but in spite of a great many articles saying otherwise, it's not for the faint-hearted.

The problem with Asterisk is that while it provides easy access to a host of telephony functions, you need to know a lot about business telephone systems to take full advantage of the system. Asterisk is a real IP-based PABX, and even though it has a GUI to cushion users from the demands of a text-based interface, you still need to understand PABXs to set up and use Asterisk.

However, it's worth remembering that you'll save a considerable amount of capital spend, which might compensate for the need for a professional to configure the system for you. At its simplest, an Asterisk system only needs a machine to run the software and an IP connection. It can now run on all major operating systems (Windows, Mac and Linux). Mac users, however, will find it harder to find PSTN line cards: the most common line cards are designed for Intel PC buses.

The alternative is to use a VoIP system from a commercial vendor - many of which have developed SME-targeted systems.

Other SME VoIP systems come from the more traditional PABX and networking suppliers -  Alacatel-Lucent, Siemens, 3Com, NEC, Avaya, Netcomm, Linksys, D-Link, Trixbox, Zultys, Panasonic, Mitel, Digium and a host of other vendors are now playing in the SME VoIP market.

Some of these are, in fact, pre-packaged Asterisk systems designed to hide the complexity from users, while taking advantage of the low cost of the open source system (Digium, which first wrote Asterisk, as well as Trixbox and 3Com, all have Asterisk "appliances" suitable for SMEs).

So what do you need to consider in choosing a VoIP system vendor?

PSTN Connectivity

The first question is whether you want to run VoIP and PSTN connectivity at the same time. There are good reasons for the business to maintain at least one PSTN line, not least because if the VoIP system fails, you'll still want to make outbound calls.

If you want to maintain a PSTN service, you'll need to choise a VoIP system that supports at least one PSTN port (usually referred to as an FXO, or "Foreign eXchange Office", port). If you're going to run a "pure VoIP" system with no PSTN connection, you don't need an FXO port.


Most of the VoIP systems designed for SMEs are highly integrated "single box" solutions. The question of integration is still important, however.

For example, some such systems are designed to work in particular environments (such as Microsoft's Response Point). This gives you the benefit of easy integration with capabilities on your office LAN, but only if that suits your business's IT strategy.

All of the VoIP vendors named above have at least basic configuration, management and operational functions built-in, with bundled applications for features like voicemail, reception, call analysis and so on. But if there are requirements specific to your business - for example, if you want to place calls directly out of your existing sales team's address books - then you'll need to make sure you can integrate the voice system with your software.


The flipside of integration is openness. Sure, VoIP is VoIP, backed by a suite of open standards - but there's still plenty of room for vendors to tie up customers with proprietary technologies and extensions.

A good example is in telephone setup. Business VoIP phones aren't trivial to set up; at the very least, from the moment you plug the telephone in, you'll need to tell the phone the address of its VoIP server, its own extension number, and the address of the server assigning IP addresses in your network.

Most vendors help speed the setup by letting phones download their config from the server - but only if the phone comes from the same vendor as the system. This can constrain what you're able to do. Inconvenience in the choice of desktop phones might not matter, but an excessively-closed system will make a big difference if you want to run softphones. For example, if your vendor only ships Windows softphones and you have Mac users, you'll want to know whether you can use a third-party softphone with your chosen VoIP system.

Size and Scaleability

Phone systems offered to SMEs don't have a great reputation for scalability, and that's something which changes profoundly in VoIP. While you can only plug in as many extensions as you have LAN ports available, Ethernet switches are cheap compared to old-fashioned PABX line cards.

VoIP system scalability instead depends on a mix of real limitations and artificial ones. The biggest real limitation is processing power - how many simultaneous conversations can the system's processor, memory and I/O handle?

For most SMEs, this may never be an issue. Even a midrange server can easily run Asterisk for 50 to 100 extensions, since it's very unlikely that all your extensions will be in use at the same time. So for a small company of 20 staff, most VoIP systems might almost be considered infinitely scalable: you're never going to run out of headroom on the system as it came off-the-shelf. Expansion costs are easily predicted: how much do I pay for an extra handset?

Buyers of "packaged" office VoIP systems are much more likely to run into what might be considered "artificial" constraints on system scalability - the number of extensions the vendor has decided a particular system should support. Once you've reached the limit of a base system, you'll either have to buy extra client licenses (if the system offers extra licenses as an expansion option) or buy a new system (if not).

There are systems even at entry level prices (around $1,500) that can support 100 extensions, so scalability may not an issue for many SMEs, but you need to know what constraints you'll be working under.


Investigate warranties carefully before you choose a system - and in particular, take a look at how different vendors treat firmware upgrades.

Compared to a PABX, a VoIP system is primarily a computer, and that means it's going to be checking for upgrades with the vendor's system from time to time. That's fine - except that some warranties (the author is speaking from personal experience here) explicitly exclude firmware upgrades undertaken by customers.

This can put the user in a bind: if the system wasn't installed by a reseller, then you'll be responsible for undertaking your own firmware upgrades. In that case, you'll want to know that your vendor doesn't walk away from a warranty after firmware upgrades. If you've purchased the system from a reseller, make sure you know whether you're allowed to undertake firmware upgrades, or whether you have to call on the reseller to install new firmware for you.


Last of all, don't forget: systems break. VoIP systems aren't just subject to hardware failures: for the ordinary user, it's hard to tell whether a system needs a reboot, or a new hard drive, or if there's something wrong with the network rather than the system.

At the very least, make sure that your system has good enough support that you can get new components quickly if there is a hardware break.

If you're implementing the VoIP system on a D-I-Y basis, you should also look for a vendor with a support line you can call in Australia - because there's no guarantee that an international support number from a minor vendor will operate to Australian business hours.

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