Healthy VoIP Nets�Part II�Network Management Architectures

Our previous tutorial began our series on VoIP network management, and looked at the five functional areas of network management that are defined by the International Organization for Standardization (ISO) as part of their research into the seven-layer Open Systems Interconnection (OSI) model. In review, these five areas are: fault management, accounting management, configuration management, performance management and security management.

But let’s take a step back for a moment, and assume that voice communications is only one element of your enterprise communications responsibilities. You are likely dealing with some type of centralized or distributed computing system, local and wide area data networks (LANs and WANs), Internet access, and possibly a video conferencing network. You many also have deployed integrated applications, such as call centers or unified messaging, which depend on a mix of voice and data elements. So when we consider these five network management areas, we need to discuss them in the context of the integrated enterprise network, not merely a singular function.

If we look at this enterprise challenge from a historical perspective, the network management business of a decade or two ago was dominated by two industries: the mainframe computer vendors and the telecommunications providers.

You may have heard of IBM’s NetView, Digital Equipment Corporation’s Enterprise Management Architecture (EMA), and AT&T’s Unified Network Management Architecture (UNMA), that fit the mold of a centralized management system that would allow input from distributed elements such as a minicomputer (in DEC’s case) or a PBX (in AT&T’s case).

But as networking architectures became more distributed, network management systems had to evolve as well. Instead of a centralized system, where all system performance information was associated with a large system—such as the mainframe or a PBX—distributed models, based upon client/server networking were developed.

With this shift toward distributed computing, the 1990s also brought about the development of two different architectures and protocols for distributed systems management.

First, the ITU-T furthered the ISO’s network management efforts, publishing a network management framework defined in ITU-T document X.700 (see

Also defined was a network management protocol that would facilitate communication between the managed elements and the management console, called the Common Management Information Protocol, or CMIP, which is defined in other X.700-series recommendations (of which there are many).

Management of telecommunications networks in particular is addressed in an architecture called the Telecommunications Management Network, or TMN, which is defined in the M.3000-series of recommendations, and specifically detailed in M.3010 (see This architecture provides a framework for connecting dissimilar systems and networks, and allows managed elements from different manufacturers to be incorporated into a single management system. This architecture has been most popular with the telcos, likely owing to their allegiance to the ITU-T, and its emphasis on telephony-related research and standards.

The 1990s also brought about the Internet surge, and with that came a friendly rivalry between some of the incumbent standards bodies (such as the ISO and ITU-T) that many considered slow and bureaucratic, and the Internet Engineering Task Force (IETF), that was more likely to be on the cutting edge and therefore quicker to respond to new innovations.

Also at that time, the networking community was patiently waiting for computing and communications vendors to embrace the seven-layer OSI model in their products, and after a few years, grew impatient. That environment gave rise to the development of the IETF’s own network management architecture, called the Internet Network Management Framework, and an accompanying protocol, the Simple Network Management Protocol, or SNMP, first documented in RFC 1157 (see This network management system embeds simple agents inside networking devices, such as IP PBXs, gateways, and servers, which report operational status and exception conditions to the network manager, which provides oversight for the enterprise or a portion of that enterprise. Communication between agents and manager is handled by the SNMP.

But no matter how large your enterprise, and the breadth of existing network management systems that you have deployed to support mainframe, WAN, or LAN environments, it’s not likely that those existing systems can adequately manage a VoIP networking infrastructure. And the reason is pretty simple—traditional networking management focuses on the systems, making sure that disk storage is adequate, the CPU is not over-utilized, a WAN link has sufficient capacity, or the number of collisions on the Ethernet LAN is not excessive. By contrast, VoIP networks must focus on the real-time conditions of the end users. In other words, the performance management, since it must be measured in real time, is a crucial factor.

Our next tutorial will consider this real time performance challenge in more detail, examining the end user perceptions of voice quality that make the management of a VoIP environment more challenging than that of traditional LANs or WANs.

Copyright Acknowledgement: © 2007 DigiNet Corporation ®, All Rights Reserved

Author’s Biography
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.

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