Chapter 2. Network Considerations when Implementing Asterisk

The reasons for choosing a Voice over IP (VoIP) telephone system in preference to a traditional PBX are many, as evidenced by the growth of IP-capable PBXs in larger businesses for some years now. One of the reasons is the opportunity it affords a business to maximize the investment it has made in its IT infrastructure. Rather than create and maintain one mechanism for transporting computer communications traffic, and another for transporting voice communications traffic, a company can simplify matters by carrying all communication traffic on a single, IP-based network.

However, putting all such traffic through one channel means that it is more important than ever to ensure it is up to the task. The irony is that, should you have to choose between an IP data network and an analog voice network based on stability, then the likely choice would be the voice channel. After all, most people have higher expectations of telephone infrastructure than of computer networks—they expect the phone to work, every time. Therefore, over time, pure voice communication transport mechanisms (initially analog but for some time now digital in nature) have developed with the emphasis very much on stability and availability above all else. This has meant that simplicity is preferable, and change is slow to occur. Of course, when designing a network with stability as the prime goal, having only one type of traffic to carry helps enormously.

But the voice channel is not suitable for network traffic, unless you hanker for a return to modems on every desk. The IP-based Ethernet network, on the other hand, is now eminently capable of being used for voice traffic. Indeed, some of the features of IP networks, such as the ability to choose between multiple routes on the fly, introduce elements of redundancy that have previously been difficult and/or expensive to add to voice networks.

In this chapter, we will look at the considerations you need to bear in mind when introducing a Voice over IP system to a company. We will discover what makes the difference between giving your customer a telephone setup that rivals a good circuit switched system for call clarity and uptime, while improving the features and capabilities many fold. After all, most people will not judge your shiny new phone system a success if they cannot simply pick up the phone, dial a number, and have a conversation.