Our previous two series of tutorialswhich lasted over a yearlooked at switching systems and session border controllers from a variety of vendors. So assuming that at least one of those vendors had a system that met your enterprise's requirements, you may be reading this as you plan the implementation phase of your VoIP rollout. Or if your VoIP network is already up and running, you may have other issues that are nagging at you, such as multi-vendor system interoperability, quality of service, or network capacity.
The common thread with all of these issues is network management, and the question of "how wellor how poorlyis your VoIP network performing?" Are the results as you anticipated (or were promised) when you signed the contract? How can you know for sure? We will explore these, and many other are concerns in the course of this next series of tutorials.
Let's jump in with a review of network management theory, and some guiding principles from an industry standard that is considered a classic.
We are all familiar with the Open Systems Interconnection (OSI) Reference Model, defined by the International Organization for Standardization (ISO), which divided the tasks of computer-to-computer communications into seven well-defined layers. This model is specified in ISO 7498-1, with the first edition published in 1984, and revised in 1994 (see http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=20269&ICS1=35&ICS2=100&ICS3=1).
An accompanying (and perhaps much less frequently read) part of that standard defines a Management Framework for computer networks, and is specified in ISO 7498-4, published in 1989 (see http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=14258). Much as the OSI Model divides a complex computer communications task into seven distinct elements, this Framework places the processes of network management into five Specific Management Functional Areas. Let's look at these areas individually, and in doing so, apply them to the management of VoIP enterprise networks.
The standard says that fault management "encompasses fault detection, isolation and correction of abnormal operation of the OSI environment." The operative word here is abnormal, derived from the Latin prefix a (not) plus normalis (normal), or in other words, not normal. But in order to determine what is not normal, you need to have a good handle on what is normal, so that when your network management system flags a problem on your VoIP network, such as an unusually high communication link utilization, you are better prepared to react.
The standard states that "accounting management enables charges to be established for the use of resources in the OSI environment, and for costs to be identified for the user of those resources." A good portion of marketing hyperbole is spent discussing the financial benefits of VoIP networks, and the promise that a single (or converged) voice-and-data network will be more economical to operate than two separate and distinct networks. Does your network management strategy include a way to measure these claims?
The standard says that "configuration management identifies, exercises control over, collects data from and provides data to open systems for the purpose of preparing for, initializing, starting, providing for the continuous operation of, and terminating interconnection services." Most enterprise managers are all too familiar with the term MAC, which stands for Moves, Adds and Changes. One of the benefits of the converged network is that a central point for network administration should result in a lower administrative overhead. Has this been your experience? Would a system that eased some of these administrative burdens be beneficial?
The standard states that "performance management enables the behavior of resources in the OSI environment and the effectiveness of communication activities to be evaluated." The key word here is effectiveness: Are the systems that you have put in place performing as well as they should? Is the quality of your voice calls equal or better to the Time Division Multiplexing (TDM) system that you just replaced? Would the choice of a different codec option improve your end user's experience?
The standard says that "the purpose of security management is to support the application of security policies by means of functions which include the creation, deletion and control of security services and mechanisms; the distribution of security-relevant information; and the reporting of security-relevant events." Quite a mouthful here, but it might boil down to an easier question: Now that voice and data are sharing a common infrastructure, how hacker-proof is your voice network? Have you assured a reasonable level of security without placing unnecessary burdens on your end users?
One parting question: Have you given some thought to each of the network management areas detailed above? If you are like most enterprise managers, you may be strong in a couple of areas, acceptable in one or two more, and weak in the rest.
So that brings us to your homework assignment: Evaluate how your VoIP enterprise would rate in each of these areas, and make a mental note to look for network management systems and tools that can help fill in those gaps.
Our next tutorial will consider these five areas in greater detail, and look at some of the network management architectures that have been successfully deployed for both voice and data network applications.
Copyright Acknowledgement: © 2007 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.