It's actually very similar to v4, just with more bits. It has an identical network model to v4: routing and address assignment work the same way. It works over

It's actually very similar to v4, just with more bits. It has an identical network model to v4: routing and address assignment work the same way. It works over the same L2 links as v4, and L4 protocols like TCP and UDP all work the same. DNS is the same. The socket API is the same. Link-local addresses exist in v4 too, and v4 even had router advertisements already before v6 was even out. If they intended v6 to be as different as possible to v4, they wouldn't have designed it to work mostly like v4 with bigger addresses. They could've given it variable length addresses, or a locator/identifier split, or any number of other useful features that would've made it different to v4... but they didn't.