 Once the UE becomes active the SGW should send an Router Advertisement immediately to the UE, otherwise the default router in the UE might timeout before the SGW would otherwise send its periodic unsolicited Router Advertisement. Renumbering the IPv6 prefixes on the link without re-establishing the PDN Connection is not supported. According to the Internet Engineering Task Force (IETF) Proxy Mobile IPv6 (PMIPv6) specification [6, 7] a Mobile Access Gateway (MAG) is the first-hop router for the mobile node. This implies that the MAG, which in 3GPP architecture is located in a SGW, decrements the Hop-Limit/Time To Live (TTL) value of each IP packet that it forwards. Similarly, the Local Mobility Anchor (LMA), which in 3GPP architecture is located in a PGW, decrements the Hop-Limit/TTL value of each IP packet it forwards. Whether the SGW should decrement the Hop-Limit/TTL value is (purposely) left unspecified in the pre- Release-11 3GPP specifications [5], and therefore, there are two different interpretations and implementations around. Figure 4.4 illustrates the PMIP-based S5/S8-interfaces. The dashed lines in the SGW show the controversial part of the 3GPP defined PMIP link-model. Deploying IPv6 in 3GPP Networks On the other hand, 3GPP specifications [25] are clear that the SGW, for example, originates Router Advertisements. The 3GPP specifications [16] are also clear that the SGW has to implement a Dynamic Host Configuration Protocol version 6 (DHCPv6) relay [26] function and the PGW then implements the DHCPv6 server function, which again makes it clear that the SGW is a router when PMIP-based S5/S8-interface is used. The end result is rather unfortunate functional disparity between the PMIP-based and GTP- based EPC networking nodes, which has already caused potential interoperability issues when integrating other non-3GPP access technologies into the EPC (such as - Wireless Local Area Network (WLAN)) [18] or deploying DHCPv6 Prefix Delegation (PD) [27, 28] over PMIP-based S5/S8-interface. The 3GPP Release-11 f