Internet Protocol version 6 (IPv6) changes many of the operating details of IP, but most of the basics are the same. In particular, devices still need to deliver datagrams over an internetwork that may use different underlying network technologies. This means that we must be concerned here, as we were in IPv4, with the mechanics of datagram sizing, handling fragmentation and reassembly, and dealing with issues related to routing.

In this chapter, I complete the discussion of IPv6 by examining these matters, with an eye toward contrasting how they work in IPv6. This includes a look at IPv6 datagram sizing, changes to the maximum transmission unit (MTU), and fragmentation and reassembly. I also briefly discuss areas where IPv6 routing is performed in the same way as in IPv4, as well as where routing has changed.