routers only need to know the address spaces out each port, it's not source routing

this is why DHT can only do so much, at best a mechanism for matchmaking, the transport still needs ARP tables and whatnot

ipv4 or ipv6 the architecture is the same, there is backbones, then there is network zones and then subnets and then LANs at the edge

the biggest difference with ipv6 is the LANs have got enough addresses to not need NAT

traffic still travels the same way, you just pipe it out the interface that has the matching netmask