d on and published the 'IPv6 Node Requirements' document that lists the main requirements for the IPv6 enabled nodes - be they hosts or routers [1]. IETF RFC 6204 defines further requirements for customer edge routers (but does not cover core Internet routers) [2]. Also other organizations have defined sets of required RFCs, for example, RIPE has published 'Requirements for IPv6 in ICT Equipment', RIPE-554 available athttp://www.ripe.net/ripe/docs/current-ripe-documents/ripe-554. In the end, despite the requirements list or profiles, each individual implementation needs to choose the exact set of protocol features deemed necessary for the use cases of each implementation. IETF has also documented the basic IPv6 components needed on 3GPP accesses in RFC 3316 [3], which is rather old but is being updated. In this book, we list 3GPP User Equipment (UE) specific requirements in more detail in Section 4.7. When IPv6 was designed, it was planned to be deployed in parallel with its predecessor Internet Protocol version 4 (IPv4) and therefore is not directly compatible with IPv4. A set of tools has been developed to provide interoperability between IPv4 and IPv6, which Deploying IPv6 in 3GPP Networks: Evolving Mobile Broadband from 2G to LTE and Beyond, First Edition. Jouni Korhonen, Teemu Savolainen and Jonne Soininen. © 2013 John Wiley & Sons, Ltd. Published 2013 by John Wiley & Sons, Ltd. Deploying IPv6 in 3GPP Networks are described in Section 5.3.1 of this book. In this section we will solely focus on the IPv6 core protocol features. 3.1 IPv6 Addressing Architecture An important benefit of the large IPv6 address space is that it allows versatile addressing architecture. The 'IP Version 6 Addressing Architecture' RFC 4291 [4] and 'IPv6 Scoped Address Architecture' RFC 4007 [5] describe the main architecture, which is then further defined in various documents that make smart use of the bits provided by the IPv6 address. In this section we will provide an overview of the addressing architecture. 3.1.1 IPv6 Address Form