Our current topic is the design and implementation of a VoIP network. In our previous tutorial, we discussed the design phase, and the requirement to be able to estimate the amount of additional traffic load that voice and video traffic would place on an existing Internet Protocol (IP)-based internetwork. We also discussed how traffic analysis and modeling software, such as the tools from Westbay Engineers, Ltd. could assist in that effort. This tutorial continues that discussion, and examines some of the network implementation issues that should be considered as you are getting your VoIP network up and running.
Understand Intranet vs. Internet: Voice over your corporate intranet and voice over the worldwide Internet are not the same thing. In the case of your intranet, you, as the network manager, can exert some control over the number of hops between two pointsand the ensuing latencies. In contrast (as we have discussed extensively in earlier tutorials), the Internet was not designed for time-sensitive traffic that demands low delays. As a result, traffic that traverses the Internet must take whatever capacity is available at the time. Therefore, get a good handle on your objectives. Are you willing to spend the effort to reconfigure your intranet as required to support voice, or are you simply looking for a lower-cost alternative for voice transport? Understand the various tradeoffs between intranet and Internet transport, as each may take a separate implementation path, affecting the scope of your project.
Do your homework: For most network managers, the voice world, with its own applications and standards, is new territory. For example, are you familiar with analog and digital trunk circuits, dialing plans, and other implementation-related issues? If not, start learning. Many VoIP vendors and trade groups have Web sites with a wealth of information, including white papers, case studies, primers on standards, newsletters, evaluation copies of client software, and so on.
Tap your enterprise experts: Do you have colleagues, perhaps in other divisions, which have already undertaken a VoIP rollout at their location? Pay them a visit, and see what they've learned. It is quite likely that they will have vendors to suggest (or avoid), know of software patches that are required, memory upgrades that are necessary, and the like. Their network may be quite similar to yours, so see if you can get a jumpstart by leveraging their experience.
Check your local resources: In many cases, the voice communication and data/networking responsibilities are handled by separate departments. Each may have a separate budget, and an empire to match. But there are likely two areas of expertise as well: circuit switching and traffic analysis for the voice side, and packet switching and IP knowledge on the networking side. Both of these skill sets are required for a successful VoIP implementation, so encourage these two groups to collaborate, and tap into your existing resources.
Inventory your toolbox: Your end users will likely judge the success or failure of the converged network implementation based, in part, on their current perception of the telephone industry, which is known for high-quality, reliable service. (Recall that the number of 99.999 percentor "five nines"of reliability is an often quoted statistic.) Thus, in addition to managing the hardware and the software elements of the network, the net manager must also consider the end users' expectations of service and reliability. To do this effectively, performance details regarding the various VoIP network elements should be measured, such as packet delay and packet loss, signal/noise ratios, and other statistics that affect voice and data transmission quality. The ability to baseline the network and identify service-affecting trends as they develop are also key ingredients for optimum performance tuning. Do you have performance tools, such as network monitors, analyzers, and management consoles available that can give you an objective window into the operation of your converged network? If not, get some tools on order, so that you will be in a position to test the VoIP network once all the piece parts start coming together.
Our next two tutorials will continue the discussion of various aspects of VoIP network implementation.
Copyright Acknowledgement: © 2005 DigiNet ® Corporation, All Rights Reserved
Mark A. Miller, P.E. is President of DigiNet ® Corporation, a Denver-based consulting engineering firm. He is the author of many books on networking technologies, including Voice over IP Technologies, and Internet Technologies Handbook, both published by John Wiley & Sons.