and capabilities in the UE and the network side have to be met. The flowchart only includes those transition tools that are either part of the 3GPP system architecture or otherwise seen useful in this problem space. Transition tools defined in IETF that aim to transport IPv6 over IPv4 are all excluded. Here we also consider dual- stack [2] as a transition tool. It should be noted that several of the flowchart's transitions reflect the UE capabilities for activating a specific type of a PDN Connection or supporting a specific transition solution. 5.3.1 Transition Solutions Not Included Effectively all tunneling based tools that would be terminated on a UE, be that IPv6- over-IPv4 or IPv4-over-IPv6, are effectively considered irrelevant for the 3GPP access for the reasons listed in Section 5.2.2. That said, it is certainly possible for the UEs to implement tunneling solutions if, for example, they need to always have access to IPv6 IPv6 Transition Mechanisms for 3GPP Networks or they utilize IP mobility solution not provided by the access network operators. For example, UE can have Dual-Stack Mobile IPv6 (DSMIPv6) Mobile Node (MN) software installed [22, 23] and access to a Home Agent (HA) somewhere. It is thus recognized that for special cases and needs, the benefits of tunneling can outweigh the drawbacks. In addition, the increase of sharing, tethering, the Internet connection via a broadband mobile network over for instance Wireless Local Area Network (WLAN) means that the operating system might not even know that its Internet connectivity is provided by a 3GPP network. Some operating systems automatically try to get access to IPv6 using a multitude of transition tools. Additionally, we do not pay attention to various (some very ingenious) solutions that are designed to prolong the lifetime of IPv4. On the other hand, any means of keeping IPv4 alive and functional would be in the scope of dual-stack. As we know, dual-stack does not solve the IPv4 exhaustion problem in a short term or actually ever. The only lon