Closing the IPv6 First-Packet Gap with Grand

IPv6 has an asymmetry in Neighbour Discovery where hosts can immediately reach routers after configuring a new address, but routers may not yet know how to reach the host, causing the first return packets to experience latency or be dropped while address resolution occurs. GRAND (a mechanism implemented in FreeBSD) fixes this by having hosts proactively advertise their addresses to routers, eliminating the "first-packet gap" and making the address resolution process transparent to applications.