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 TCP/IP Remote Network Monitoring (RMON)
 (Page 2 of 3)
 RMON MIB Hierarchy and Object Groups Since RMON is a MIB module, it consists 
almost entirely of descriptions for MIB objects, with each having the 
standard characteristics belonging to all such objects. All the objects 
within RMON are arranged into the SNMP object name hierarchy within 
the rmon group, which is group number 16 within the SNMP mib 
(mib-2) object tree, 1.3.6.1.2.1. So, all RMON objects have identifiers 
starting with 1.3.6.1.2.1.16. This single RMON group is broken down 
into several lower-level groups that provide more structure for the 
RMON objects defined by the specification. Figure 286 
shows this structure. 
 Figure 286: SNMP Remote Network Monitoring (RMON) MIB Hierarchy RMON uses a special MIB module, rmon(16), which fits into the overall SNMP object hierarchy tree under mib/mib-2(1) within mgmt(2)just like other MIB object groups such as sys(1) and if(2); see Figure 273. Within this group, which has the group identifier 1.3.6.1.2.1.16, are 9 subgroups of RMON objects. 
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 Table 222 
describes each of the RMON groups, showing for each its name, its group 
code (which is used as the prefix for object 
descriptors in the group), and its RMON 
group number and SNMP object hierarchy identifier: 
 Table 222: SNMP RMON MIB Object Groups  
| RMON Group 
Name | RMON Group 
Code | RMON Group 
Number | Full Group 
Identifier | Description |  
| statistics | etherStats | 1 | 1.3.6.1.2.1.16.1 | Objects that keep track of network 
statistics measured by the device. Example statistics include network 
traffic load, average packet size, number of broadcasts observed, counts 
of errors that have occurred, the number of packets in various size 
ranges and so forth. |  
| history | history, 
etherHistory | 2 | 1.3.6.1.2.1.16.2 | The history 
group contains a single table object that controls how often statistical 
data is sampled by the probe. The additional etherHistory group 
is optional and contains extra Ethernet-specific information; it is 
contained logically within the history group. |  
| alarm | alarm | 3 | 1.3.6.1.2.1.16.3 | This group defines the parameters 
under which an alarm may be generated to inform an administrator of 
an occurrence of import. The alarm group contains a table that 
describes the thresholds that will cause an event to be triggered (see 
the event group below). |  
| hosts | host | 4 | 1.3.6.1.2.1.16.4 | Contains objects 
that keep track of information for each host on a network. |  
| hostsTopN | hostTopN | 5 | 1.3.6.1.2.1.16.5 | This group contains objects that 
facilitate reporting of hosts sorted in a particular way. The administrator 
determines how these ordered statistics are tracked. For example, an 
administrator could generate a report listing hosts sorted by the number 
of packets transmitted, showing the most active devices. |  
| matrix | matrix | 6 | 1.3.6.1.2.1.16.6 | This group 
keeps track of statistics for data exchanges between particular pairs 
of hosts. So, the amount of data sent between any two devices on the 
network could be tracked here. Since a large network could have thousands 
of such device pairs, to conserve resources on the probe, often only 
the most recent conversations between device pairs are kept 
in the management information base. |  
| filter | filter | 7 | 1.3.6.1.2.1.16.7 | This RMON group allows an administrator 
to set up filters that control what sorts of network packets the probe 
will capture. |  
| capture | buffer, 
capture | 8 | 1.3.6.1.2.1.16.8 | This group 
is used to allow a probe to capture packets based on particular parameters 
set up in the filter group. |  
| event | event | 9 | 1.3.6.1.2.1.16.9 | When a particular alarm is triggered 
based on the parameters in the objects in the alarm group, an 
event is generated. This group controls how these events are processed, 
including creating and sending an SNMP trap message to a network monitoring 
station. | 
 The original RMON standard 
was heavily oriented around Ethernet LANs, and you can see some of that 
in the table above. Probes can also gather and report information related 
to other networking technologies, by using other RMON groups created 
for that purpose. The best example of this was the definition of a set 
of groups specifically for Token Ring, which was defined in RFC 1513 
in 1993. 
 
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