Answer: If the timeout value is too small, we clutter the networ k with unneces-
sar y re-requests, and halt transmission until the re-request is answered. When
a hosts Ether net address changes, eg because of a card replacement, then that host is unreachable to others that still have the old Ether net address in
their ARP cache. 10-15 minutes is a plausible minimal amount of time required
to shut down a host, swap its Ether net card, and reboot.