Handbook of Local Area Networks, 1998 Edition:LAN Management










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Many LAN management tools are designed to interoperate with other LAN management tools, relying upon standardized network management protocols to do so. In a distributed environment typical of most LAN installations, this is particularly important. One of the more recent advances in standardization of network management protocols is the focus of Chapter 7-1, “The Remote Network Monitoring (RMON) Protocol: The Perfect Complement to SNMP.” While network management has been a challenge since the earliest days of LANs, technology continues to evolve. A subtle, but pervasive paradigm shift is taking place as switching becomes a more integral part of network design. As switching technology, discussed in several sections throughout this Handbook, continues to make its way into LAN installations, management of switched networks will become increasingly important to LAN managers. Such is the focus of Chapter 7-2, “Managing Switched Internetworks.” An often-overlooked, and largely hidden, characteristic of LAN management systems is their use of object identifiers. Also known as the global naming tree, an understanding of the object identifier tree structure and the addressing method used to locate network devices can make it easier for LAN administrators to effectively support different management systems. Chapter 7-3, “Managing Networks with the Global Naming Tree,” provides an examination of this topic. Not all uses of LAN technology are as immensely popular as electronic mail or the World Wide Web. Some are nearly taken for granted despite the immense value they bring to an organization. An example of this is a function often provided by a LAN support department: networked data storage management. A number of tools and pieces of equipment can aid in this task, yet one element that is all too often overlooked is the definition of backup procedures. Chapter 7-4, Network Data and Storage Management Techniques,” discusses a number of backup strategies, along with their pros and cons. Finally, no matter what set of tools and practices an organization employs for the purpose of LAN management, the support provided will be no better than the human beings put in place to provide the support. Chapter 7-5, “Structuring a LAN Support Department,” deals with the human side of LAN support. While each organization has its own needs, culture, and style, certain basic support services are required of every LAN support department. This chapter address issues that should be taken into account. 7-1The Remote Network Monitoring (RMON) Protocol: The Perfect Complement to SNMP FRANK HENDERSON The simple network management protocol (SNMP) has become the de facto standard in the US for network management. SNMP users network and systems polling devices to query the status of network elements (see Exhibit 7-1-1). The management workstation queries network elements for data — contained in their management information bases (MIBs) — and the MIBs send a response. The only exception to this passive polling is the trap command. The trap command allows network elements to send unsolicited responses to the management console in case of emergencies. Unfortunately, the trap messages are not standardized among vendors, which diminishes their usefulness. Exhibit 7-1-1.  Simple Network Management Protocol (SNMP v1) When SNMP is used for small networks (less than 100 network devices), the amount of overhead for polling is acceptable. However, as networks increase in size, the polling interval must increase to provide a granularity of MIB-variable elements. Unfortunately, this increases overhead, and it wastes polling cycles because there is only the trap mechanism for management by exception. The increase in size of the average network has created the need for remote monitoring of network segments on an exceptions-only basis. This need is being met today by the remote monitoring (RMON) protocol. RMON AND AGENT TECHNOLOGY RMON is an important subtype of intelligent agents. Intelligent agents act at the direction of the SMNP manager and provide data and filtered information only when it is required. The questions asked within network management concerning error packets, broadcasts, and other network elements have not changed, and information is traveling shorter distances. These agents can be positioned between SNMP managers, network devices, and LAN segments to reduce the polling overhead in an enterprise network. RMON: The Beginning The data communications industry has relied on the protocol analyzer for many years. There are several effective analyzers on the market, however, they each collect data in their own particular format. It is difficult to integrate that data with SNMP management consoles. Therefore, LAN analysis has been costly and not as comprehensive as network administrators would like. In late 1989 and 1990, several protocol analyzer vendors joined Steve Waldbusser of Carnegie Mellon University to develop an extension of SNMP. The fist standard addressed only Ethernet LANs, and the group defined nine categories — or functions — to provide interoperability between the software and hardware offerings of heterogeneous vendors. The remote network monitoring protocol was integrated with SNMP’s structure of management information (SMI). (See Exhibit 7-1-2). Exhibit 7-1-2.  RMON Structure of Management Information (SMI) Tree Structure The RMON MIB for Ethernet, RFC 1271, was published in November 1991. SNMP has been extended to the systems environment (most directly in the host MIB). Exhibit 7-1-3 delineates the capabilities of RMON compared with other MIB standards. Exhibit 7-1-3.  MIB Comparisons Previous Table of Contents Next Use of this site is subject certain Terms & Conditions. Copyright (c) 1996-1999 EarthWeb, Inc.. All rights reserved. Reproduction in whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Please read our privacy policy for details.