Technologies: SIP | QOS | XML | POE | Asterisk | Shoretel
VOIP is a a technology that makes the convergence of voice and data onto one network possible. More and more organizations (and consumers) are adopting one or another form of this wonderful evolution of communication. There are plenty of off the shelf options on the market and depending on your budget, patience and functional need the "right" fit can be a relative choice.
In my experience as a Network & Information Technology Manager I have been given the opportunity to review and implement a few different options both commercial and open sourced.
From the commercial angle I have implemented multi-site solutions using products from Shoretel. Shoretel makes a very robust product that can scale with an organization to almost limitless numbers - all while never making equipment non-compatible. This feature alone makes Shortel a clear winner in many conversations. An easy to use administration UI, a nice desktop call presence application, global directories and a full set of call handling options have made Shoretel a very serious competitor in this space.
The downside to any commercial solution is an almost never ending license discussion and of course the problem of proprietary hardware. While most of these problems are eliminated by going the open source direction a new set of problems can arise (support, junky interfaces, limited understanding, etc). When we made considerations of evaluating Asterisk as an alternative voice solution we were careful to evaluate only options for wich we could get support. Asterisk is a very popular solution that has a proven track record in this space, but that does not mean it is right for everyone.
Our implementations consit of a handful of Digium appliances and a larger network of appliances based on Elastix (a commonly deployed package). The installations are trunked together (including Shoretel) using SIP trunks which results in lower toll based calling and better utilization (reduced) of PSTN interfaces. The handsets we most commonly elected to deploy are Polycom due to their XML based auto-provisioning functionality and wide support of POE. Analog interfaces were most commonly provided by Sangoma due to their ease of use and proven performance.
As you can imagine, making these projects work well relies upon proper configuration of all equipment in the call path. All of the proper bandwidth management (QOS) techniques were employed using a selection of network gear from Cisco, HP, Watchguard, Netgear and a few others. A semi-diverse set of analog and digital endpoints were used in implementations around the country. Wifi handsets, EnGenius long range wireless handsets, SIP paging gateways and analog telephone adapters were employed when the circumstances required.
In summary, my experiences with VOIP have given me a grasp on what is needed to make a deployment work and an understanding of the solutions I have implemented. If you have any questions regarding this or any other project please feel free to contact me.