ress for more than one network interface at a time. The inter-access mobility problem could be solved by adding explicit support capabilities to host operating systems. Several proposals for that have been proposed in the IETF, but none has yet to become a standard. The proposals are essentially proposing means to hide inter-access mobility from an IPv6 stack by introducing an additional layer between IPv6 and access network interfaces. This layer is often called a 'logical interface', whose purpose is to hide changes and details of real physical interfaces, thus hiding possible breaks during access switching and thereby avoiding issues with the current stacks' assumptions. The work in IETF has not been completed due to various issues related to such schemes: how are MTU differences and changes handled, how will Neighbor Discovery be managed, how can point-to-point links and shared links combined seamlessly, how are multicast transmissions handled, and SO on? It remains to be seen if PMIPv6-based inter-access mobility happens. IP Security In the early days of IPv6, support for IPsec was designed to be mandatory for all IPv6 implementations. The mandatory security support requirement was one justification for why IPv6 ought to be superior to IPv4. However, as the years passed, IPsec and especially deployment of shared Public Key Infrastructure (PKI) system, which would have been needed to get the envisioned security properties, proved to be too complex to deploy. With IPv6 implementations emerging, it soon became clear that the market decided that IPsec should be an optional feature for the stack and usually supported only when needed for Virtual Private Network (VPN) uses. Furthermore, since the 1990s, other options, such as TLS and secure shell, had become popular and diminished the need for IPsec. These facts are nowadays acknowledged even by the latest revision of the 'IPv6 Node Requirements' RFC 6434 [1], which states that nodes should - not anymore 'must' - support IPsec [125]. IPsec is described only superf