Ethernet loss measurement counter for each class in a multiclass environment

You can monitor physical link degradation (indicated by bit error rate (BER) threshold levels) on Ethernet interfaces and take corrective actions if the BER threshold value drops to a value in the range of 10-13 to 10-5. 

Layer 2 and Layer 3 protocols support the monitoring of physical link degradation. An Ethernet link also supports monitoring of physical link degradation through the Link Fault Signaling (LFS) protocol. However, for both of these monitoring mechanisms, the BER threshold value range of 10-13 to 10-5 is very low. Because of the low BER threshold value, the physical link degradation goes undetected, causing disruption and packet loss on an Ethernet link.

Junos OS supports Ethernet loss measurement (ETH-LM) for multiclass services. The ETH-LM feature is used by operators to collect frame loss counter values for ingress and egress service frames. The ETH-LM feature is extended to support the frame loss measurement counters for each class of packets in a multiclass environment. Counters for each class of packets are supported for point-to-point services only. 

ETH-LM maintains counters based on the forwarding class and loss priority of a packet. The loss priority determines the color of a packet-green indicates loss priority low for committed information rate (CIR) and yellow indicates loss priority medium-high for excess information rate (EIR). The color (green and yellow) counters are maintained for each class of packets.