IBM 8260 manual Statistics Group, Drop Events

Table 32. MIB Structure for RFC 1271 - RMON MIB for Ethernet

Group	Description
Statistics	The Statistics group provides an overview of the current segment network
	activity at any given moment. It collects segment statistics like octets, packets,
	collisions, broadcast, various error counters and packet size.
History	The History group records periodic statistical samples from a segment and stores
	them for later retrieval.
Alarm	The Alarm group periodically takes statistical samples from variables in the
	RMON agent and compares them to defined thresholds. When a threshold is
	crossed, an event will be generated. It is useful to track unusual activity or
	problems.
Host	The Host group maintains host tables by keeping a list of source and destination
	MAC addresses seen in good packets. In addition, statistics like octets and
	packets transmitted and received, errors transmitted, broadcast and multicast
	packets are kept on a per host basis. In problem determination, it is extremely
	useful for isolating the culprit by its interface address that, for instance, is
	causing the error count to rise sharply.
Host Top ″N″	The Host Top ″N″ group provides lists of a given number of hosts that meet a
	particular criteria ordered by one of their statistics. For instance, you can list the
	top 5 packet sending hosts. This helps in isolating the hosts that are creating
	network problems.
Matrix	The Matrix group monitors and stores information about conversations between
	two hosts in the network.
Filter	The Filter group allows packets of particular interest to be filtered and isolated.
	These packets can then be directed into capture buffers or used to trigger
	events. It is useful for monitoring traffic flow and setting alarm conditions.
Packet Capture	The Packet Capture group allows packets to be captured upon a filter match and
	stored for later retrieval. It can be used to view the history of packet activity in
	the event of a failure.
Event	The Event group controls the generation and notification of events from the
	RMON agent. It contains a log table that associates logged entries with a
	specific event.

10.4.1.1 Statistics Group

The Statistics group contains very useful statistical information gathered by the network probe through its Ethernet interface. The information provided by this group gives a view of the total Ethernet LAN segment activity at any given moment. It samples data and provides information by octets, packets, various error counters and packet size. The statistics take the form of free running counters that start from zero. Here is the list of statistics available under this group:

Drop Events	The number of events in which packets were dropped
	by the probe due to unavailability of resources on the
	probe itself. It doesn′t represent the number of
	packets dropped but the number of times this
	condition was detected. If the drop events counter
	constantly increments, it is an indication that there is
	more activity on the segment than can be captured by
	the network probe. You may want to consider
	increasing the resources on your network probe. For
	instance, if you are running the RMON application on
	a workstation, you may want to allocate more real

196 8260 Multiprotocol Intelligent Switching Hub