Future Network Considerations

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RMON Overview

Remote Monitoring (RMON) standards provide distributed management architecture for performing traffic analysis, troubleshooting, trend reporting, and proactive network management. Normally, a RMON probe is attached to each segment; however, with the increasing high-performance of switched internetworks, a new standard needed to be developed to handle these technologies such as Virtual LANs (VLANs) and fast Ethernet inter-switch networks. RMON2 adds several key enhancements to the already manager-friendly RMON standard. The main feature is that it extends its reach to the third layer in the OSI reference model—the Network Layer. It provides network-layer host and matrix tables for monitoring layer three traffic by host, or by conversations for various network protocols. Furthermore, it provides this new layer connectivity without sacrificing the standard RMON attributes such as: bandwidth utilization, packet rate, and rate errors. Application Layer host and matrix tables are also included in this second version, for monitoring layer seven traffic, by host or conversation for various applications. Figure 12-2 shows the coverage provided by RMON.

Figure 12-2  RMON coverage.

RMON also provides address mapping for aggregating the statistics by network address as well as MAC addresses for Ethernet and Token Ring networks.

It adds protocol directory and distribution groups for displaying selected protocols and their distribution for each LAN segment. Finally, it provides a user-defined history, which now extends beyond the Link-Layer statistics to include any RMON1&2, or MIB I or II statistics.


The RMON standard was originally created for a distributed computing architecture, in which the agents and probes communicate using a central station, normally the manager, via the SNMP protocol. The RMON standard provides a powerful management tool for performing traffic analysis, troubleshooting, trend reporting, and proactive network management. An RMON probe, or agent, is generally attached to each network segment, thus providing visibility into all network activities. The main benefit when utilizing RMON technology is increased network availability for users and high productivity for network managers.

A basic RMON system can provide the following:

  Information enabling administrators to perform analysis of network utilization, including data and error statistics
  Historical information of network trends and statistical analysis
  Matrix information describing communications between systems and the quantity of data exchanged

RMON is an extension of the reach of the network manager’s operation to other networks under his/her control. As probes, or RMON agents, monitor the flow of data on the remote network, they organize that information into a coherent format that the network manager can easily interpret and use to better manipulate the network. Figure 12-3 illustrates the function and routing of information from an RMON probe to the network manager’s workstation.

Figure 12-3  Deployment of an RMON probe.

The RMON probe monitors and organizes data flow on the remote network, reducing the amount of bandwidth required to transmit the information to the manager’s station. In doing so, this alleviates the problem associated with SNMP—the significant degradation of lower bandwidth when operating geographically separated networks. The WAN circuit used to connect the separate networks operates at a fraction of the operating rate of a LAN circuit—by reducing the potential of saturation on a WAN circuit, the overall network performance is increased.

Every RMON probe includes a MIB that defines each attribute of the object/device being monitored. RFC 1271, published in November 1991, was the first RMON MIB standard. It dealt strictly with Ethernet LANs. It provided network managers with comprehensive network fault tolerance, diagnosis, planning, and performance information. It delivered this information in nine groups of monitored elements. Each group provided specific data sets to meet common monitoring requirements. Following that, RFC 1513, published in September 1993, extended the RMON MIB to include Token Ring networks. Although RMON MIBs define the attributes of objects on the monitored networks, the value and usefulness of this information is dependent on the application the manager is using, and the extent he/she uses that information. The list that follows shows the various groups found within RMON and what they bring to your network.

  Statistics. Provides counters for packets, octets, broadcasts, errors, and offers, on segment or port
  History. Periodically samples and saves statistics group counters for later retrieval
  Hosts. Maintains statistics on each host device on the segment of port
  Host Top N. A user-defined subset report of the Hosts group, sorted by a statistical counter. By returning only the results, management traffic is minimized
  Traffic Matrix. Maintains conversation statistics between hosts and networks
  Alarms. A threshold that can be set on critical RMON variables for proactive network management
  Events. Generates SNMP traps when an Alarm group threshold is exceeded; also logs these events
  Filters. A filter engine that generates a packet stream from frames that match a specified pattern
  Packet Capture. Manages buffers for packets captured by the Filter group for uploading to the management console
  Token Ring. More specific information is as follows:
  Ring station. Provides detailed statistics on individual stations
  Ring station order. Provides an ordered list of stations currently on the ring
  Ring station configuration. Provides configuration and insertion/removal per station
  Source routing. Provides statistics on source routing, such as hop counts, and others

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OSPF Network Design Solutions
OSPF Network Design Solutions
ISBN: 1578700469
EAN: 2147483647
Year: 1998
Pages: 200
Authors: Tom Thomas

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