If you are looking to deploy IP trunking to your IP PBX, you face an array of challenging decisions. So much for the idea that things in IP are simpler than they were in the world of TDM voice. It is the benefits of IP that also create some of its biggest challenges.
The open nature of IP gives a tremendous amount of flexibility – we use IP technology to read web pages such as this one, watch YouTube videos, exchange instant messages, and make VoIP calls, among many other things. Each of these uses employs many different protocols and standards that ride atop IP. The longer those standards have been around, the more robust and defined they are. Even though the hypertext transfer protocol (better known as HTTP, a foundational protocol for web pages) has been around for many years, there are still variances in the way web browsers such as Firefox, Apple’s Safari, or Microsoft’s Internet Explorer display web sites. VoIP is a younger technology, so there are various competing standards, some more robust than others.
For IP trunking, you have a plethora of protocols to choose from. For signaling, do you use H.323 or SIP? What voice codec is best: G.711, G.729 or a wideband codec such as AMR-WB? Do you use TCP or UDP as the transport layer protocol? Do you want to implement secure protocols such as TLS and SRTP? These are just a few of the many choices, and as is typical with many engineering problems, there is no “right” answer to these questions. Rather, they all involve tradeoffs between price, performance, security and quality. For example, a high-compression codec like G.729 will not have the high quality voice of a low-compression codec like G.711; it will require more processing power and will drive up the cost and/or reduce the capacity of hardware, but it reduces the amount of network bandwidth needed.
To start, talk with your IP PBX supplier about how to optimize the investment you’ve already made, and whether a software upgrade might give you more options to better meet your needs. That said, there are a number of trends in IP trunking you should think about. SIP is clearly a preference over H.323, wideband codecs give end users a clearly audible benefit, and given the increasing security threats in IP, there is a strong trend towards improved security protocols like TLS.
IP trunking offers so many benefits that it’s hard to resist jumping right in. However, without careful planning and informed decisions, implementing IP trunking could be a very painful experience. Make sure you work closely with your equipment and service providers who have the expertise to make the transition as smooth as possible.