Refer to the exhibit. A network engineer observed congestion between routers R1 and R4, which are connected on a point-to-point link. Two servers that reside on networks on R1 and R4 generate heavy…

Traffic policing is the appropriate QoS mechanism for immediately dropping packets that exceed a defined rate threshold, especially when applied inbound on an interface. This directly addresses the requirement to 'drop inbound packets that exceed a configured threshold' on the congested R4-R1 link, where traffic from R4 to R1 is heavy.

FIFO queuing simply processes packets in the order they arrive and does not actively drop traffic that exceeds a threshold; instead, it queues it, which is contrary to the requirement of dropping excess packets.

Traffic shaping typically buffers excess packets for later transmission to smooth out traffic bursts, rather than immediately dropping them as requested.

Implementing a service policy to tag traffic is a classification and marking mechanism for QoS, not a congestion management technique that drops excess packets.