ndor but details ought to be verified. Unpleasant surprises and feature imparity compared to IPv4 functionality is still a reality. 4.6.2 IPv6 in Information Element Level At the information element level, the IPv6 support has been there from the beginning of GPRS, more or less throughout all signaling and control plane interfaces. This was Deploying IPv6 in 3GPP Networks actually the requirement to enable IPv6 support on the user plane, which has also been there, at least in the specification level, from the beginning of GPRS. We want to highlight one detail regarding the IPv6 and signaling protocols' information elements. For some reason, there is no consistency in IPv6 address representation within 3GPP. It is somehow expected that there would be discrepancy between, for example, 3GPP and IETF defined protocols. However, 3GPP has achieved multiple encoding for- mats even within the same protocol. User Equipment Specific Considerations In this section, we discuss some of the key considerations related to IPv6 support on 3GPP enabled UEs. These UEs can range from typical mobile handsets to router-class devices to Machine-to-Machine (M2M) devices. We start the considerations by listing and categorizing the required RFCs for generic IPv6 protocol support on 3GPP UEs. Due to the properties and peculiarities of 3GPP network architecture, the list of RFCs is somewhat different from what is listed by IETF in the generic 'IPv6 Node Requirements' RFC 6434 [33]. After listing the RFCs, we describe other UE functionalities for which IPv6 support has implications. 4.7.1 IPv6 and Impacted Layers The introduction of IPv6 support to UEs has profound implications to the used operating system and to a lesser extent to the applications and used chipsets. Figure 4.28 provides a high-level abstraction of these impacted layers and software modules, which we will discuss in more depth soon. The number of entities that IPv6 impacts is one of the main reasons why the introduction of IPv6 into UEs has been generally slow. Applications 