PMTUD
Path MTU Discovery (PMTUD) is a networking technique used to determine the maximum transmission unit (MTU) size that can be used on the path between a source and destination without requiring fragmentation. By learning the smallest MTU along the route, hosts can send packets large enough to maximize efficiency while avoiding fragmentation at routers.
In IPv4 PMTUD, the sender marks packets with the Don't Fragment (DF) bit set. If a router
In IPv6, routers do not fragment packets. PMTUD relies on ICMPv6 "Packet Too Big" messages to inform
Limitations and risks include dependence on unblocked ICMP traffic, potential black holes when ICMP is filtered,