IPv6 routers report oversized packets; sources decide how to fit the path
An IPv6 router does not fragment a packet while forwarding it toward its destination. If the packet is too large for the next link, the router discards it and sends ICMPv6 Packet Too Big feedback. The source can then adjust its packet size or, where appropriate, send fragments using the IPv6 Fragment header. Reassembly of those fragments takes place at the destination. ...