With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
tokenRingMLStatsDroppedFrames
token Ring ML Stats Dropped Frames
1.3.6.1.2.1.16.1.5.1.1
The total number of frames which were received by the probe and therefore not accounted for in the *StatsDropEvents, but for which the probe chose not to count for this entry for whatever reason. Most often, this event occurs when the probe is out of some resources and decides to shed load from this collection. This count does not include packets that were not counted because they had MAC-layer errors. Note that, unlike the dropEvents counter, this number is the exact number of frames dropped.
Back to RMON2-MIB MIB page.
IPHost Network monitor allows you to monitor tokenRingMLStatsDroppedFrames on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco optical switches right now.