elegated to the UE: 2001:db8:0:40::/58 Prefix 3 delegated to the UE: 2001:db8:0:20::/59 Prefix 4 delegated to the UE: 2001:db8:0:10::/60 Prefix 5 delegated to the UE: 2001:db8:0:8::/61 Prefix 6 delegated to the UE: 2001:db8:0:4::/62 Prefix 7 delegated to the UE: 2001:db8:0:2::/63 Prefix 8 delegated to the UE: 2001:db8:0:1::/64 The third alternative would be using 'unnumbered link model' [117], where the Requesting Router and the Delegating Router use only link-local addresses on the link they share. However, this model does not apply to the 3GPP link model at all and therefore is ruled out of possible solutions. Due to the link model differences between PMIPv6- and GTP-based packet core, the PMIPv6 requires a slightly different handling of delegation in a SGW/MAG after a han- dover. The solution described in [28] makes sure that the required forwarding state for delegated prefixes is updated in a target SGW/MAG. A notable achievement of DHCPv6 PD was introducing a stateful DHCPv6 server into the 3GPP packet core architecture and the PGW. Prefix Management using External DHCP and AAA Servers Delegated prefixes can be managed using the same methods that have been described earlier for /64 IPv6 prefix management. These include internal prefix pools within a PGW, external DHCPv6 server prefix pools (when the PGW implements a DHCPv6 relay or a DHCPv6 server+client combination), and external AAA server pools. Current 3GPP Release-11 specifications [8, 15, 25] implicitly assume that either PGW internal pools or external AAA servers are used for the delegated prefix management. If the DHCPv6 were used to interface external DHCPv6 servers, both the UE /64 IPv6 address (prefix) and the delegated prefix should be assigned in one DHCPv6 protocol exchange, otherwise the handling of the excluded prefix becomes even more complicated than it already is. There are few issues regarding this in the 3GPP architecture, such a procedure not even being described in the 3GPP standards. First, the UE is explicitly prohibited from perform