 with UE requested IP addressing information. When a UE supports DSMIPv6 (i.e. the S2c-interface) it may include a request for an IPv6 HNP at an NAS level. This is done including specific PCOs in the NAS signaling requests. The UE would request the IPv6 HNP only if the UE also requests the Home Agent (HA) IPv6 address. This feature is available for both GPRS and EPS since Release- 8. Section 4.4.7 will discuss the aforementioned NAS protocol information elements in more detail. 4.4.6 IPv6 Prefix Delegation IPv6 Prefix Delegation is a part of 3GPP Release-10 and is not covered by any earlier releases. However, the /64 prefix allocated for each default bearer (and to the UE) may be shared to the local area network by the UE implementing Neighbor Discovery (ND) proxy [23] or some similar functionality. The Release-10 Prefix Delegation uses the DHCPv6-based PD [27]. The model defined for Release-10 requires aggregatable prefixes, which means the /64 prefix allocated for the default bearer (and to the UE) must be part of the shorter delegated prefix. This was mainly a requirement originating from the PCC architecture, where it was desirable and feasible to treat all prefixes belonging to a single PDN Connection as one shorter aggregate prefix. It is worth noting that the lifetime of the delegated prefixes fate-share the lifetime of the PDN Connection that they are associated with regardless of the lifetime values received during the DHCPv6 PD exchange. This stems from the fact that the delegated prefix and the excluded /64 prefix must aggregate. Unless the subscriber is also provisioned with a static /64 IPv6 address, there is no guarantee that the delegated prefix would remain the same across disconnections of the PDN Connection. IPv6 in 3GPP Networks DHCPv6 prefix delegation has an explicit limitation, described in Section 12.1 of [27], that a prefix delegated to Requesting Routers (RRs) cannot be used by the Delegating Routers (DRs) (i.e. the PGW in this case). This implies that the shorter 'delegated prefix' canno