This read-only object returns the interface index number (ifIndex) of the port on which rate limiting is being applied or monitored, serving as a key identifier to link rate-limit statistics and configuration to specific physical or logical interfaces. Network operators use this value to correlate rate-limit data with other interface-based management information and to verify that traffic shaping policies are applied to the correct ports. This object is essential for mapping between different MIB tables that describe interface behavior.