This read-write BITS object selects which performance variables, such as vRSL, vBER, or vUAS, are included in the periodic keep-alive trap. An admin configures this to enrich the routine heartbeat trap with the specific link-health metrics they want visibility into without polling for them separately. For example, enabling the vRSL and vBER bits means every keep-alive trap will carry the current receive signal level and bit error rate alongside the standard heartbeat, letting the NMS trend link health passively.