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What is the proc_ base_reachable_time entry (associated with ARP)

According to arp (7) - Linux man page:

base_reachable_time (since Linux 2.2) Once a neighbor is found, the entry is considered valid for at least a random value between base_reachable_time / 2 and 3 * base_reachable_time / 2. The validity period of the application will be extended if it receives positive feedback from protocols of a higher level. The default is 30 seconds. This file is now deprecated in favor of base_reachable_time_ms. base_reachable_time_ms (since Linux 2.6.12) As for base_reachable_time, it measures the time in milliseconds. The default is 30,000 milliseconds.

I did not understand this explanation - especially the expression of positive feedback from higher-level protocols. Someone please clarify?

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On the arp page (7) ,

When there is no positive feedback for an existing mapping after some (see below), the neighbor cache entry is considered obsolete. Positive feedback can be obtained from a higher level; , for example, from a successful TCP ACK. Other protocols can signal forward using the MSG_CONFIRM flag for sendmsg (2). When not moving forward, ARP tries to reproduce.

, - TCP- ACK, , IP/MAC, , ARP, .

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IPv6 ndisc_router_discovery base_reachable_time.
IPv6 ( ARP) .

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