TABLE OF CONTENTS The IPv6 Specification (RFC 2460) and the IPv6 Addressing Architecture (RFC 2373) provide the base architecture and design of IPv6; we covered some of these key concepts in earlier sections. Sections 7.7 and 7.8 look at basic IPv6 network constructs, specifically routing processes. Because there are differences on some of the details of how these IPv6 processes operate compared with IPv4, it is worth looking at some of these issues. Related work in IPv6 that needs to be mastered by implementers and network designers includes the IPv6 Stateless Address Autoconfiguration (RFC 2462); the IPv6 Neighbor Discovery Processing (RFC 2461); the Dynamic Host Configuration Protocol for IPv6 (DHCPv6) (RFC 3315); and, the Dynamic Updates to DNS (RFC 2136). Some portions of this discussion are based on [MSD200401].
As we discussed earlier, an IPv6 Protocol Data Unit (PDU) consists of an IPv6 header and an IPv6 payload, as depicted in Figure 7.10. The IPv6 header consists of two parts: the IPv6 base header and optional extension headers. The optional extension headers are considered part of the IPv6 payload, as are the TCP/UDP/RTP PDUs. Obviously, IPv4 headers and IPv6 headers are not automatically interoperable; hence, a router operating in a mixed environment must support an implementation of both IPv4 and IPv6 to deal with both header formats. Figure 7.11 shows for illustration purposes the flows of IPv6 PDUs in a VoIP environment.
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