there could be only one instance of the PDP Address field. Since Release-9, the PDP Context information element header has an additional flag, the Extended End User Address flag, which indicates that a second instance of the PDP Address field can be found in the PDP Context information element. The second PDP Address was added for dual-stack purposes. The IPv6 address is a complete /128 IPv6 address, not just a prefix. MBMS End User Address The MBMS End User Address information element is the same as the 'normal' End User Address information element used throughout GTPv1 signaling and shown in Figure 4.12. The only difference is that the IPv6 address is now a multicast address [21]. Note that in case of IPv6 multicast addresses, the comment on the IID part of the address and its usefulness does not apply. The format of IPv6 multicast address is different from IPv6 unicast addresses - see Section 3.1 for further descriptions of unicast and multicast address format differences. The MBMS End User Address information element may appear in the following MBMS related GTPv1 messages: the MBMS Registration Request, the MBMS De-registration Request, the MBMS Session Start Request, the MBMS Session Stop Request, and the MBMS Session Update Request [9, 49]. MBMS UE Context The MBMS UE Context information element may be present in both SGSN Context Response and Forward Relocation Request GTPv1 messages that are used during the inter-SGSN RAU, inter-RAT handover and the related context transfer. The MBMS UE Context information element contains user plane IP multicast address information within the PDP Address field. Either IPv4 or IPv6 address can be included in the PDP Address field. Only a single IP family is supported and 3GPP Release-9 like dual-stack operations is not allowed for MBMS Bearers. 4.3.2 GTP Control Plane Version 2 This section goes through most, if not all, GTPv2 messages and their information elements that contain user plane IPv6 addressing information. We provide a lot of information element figures and th