2 - IPv6 Addressing Architecture

Abstract

The most well-known and important enhancement introduced by Internet Protocol Version 6 (IPv6) is the expansion of the address space as the result of increased bit allocation for an IPv6 address—that is, from 32 bits in Internet Protocol Version 4 (IPv4) to 128 bits in IPv6. The IPv6 address architecture also introduces several remarkable characteristics along with the enlarged address space, mainly from operational experience with IPv4. This chapter discusses the specification details of IPv6 address architecture and shows how KAME implements the specification in the Berkeley Software Distribution (BSD) kernel. It then provides operational examples of configuring and managing IPv6 addresses on a BSD system. It helps understand the implementation in a more solid way. The primary reference in this chapter is [RFC3513], which defines the protocol specification about IPv6 addresses. The IETF has updated the specification to [RFC4291], but the chapter mainly refers to the previous version because the implementation is based on that version. However, it tries to follow the latest standardization status with explicit notes when the implementation is different from the latest specifications. Significant changes include the deprecation of one type of limited-scope unicast addresses and updates to address format of multicast addresses.