ibutes in the case where the address/prefix allocation is entirely delegated to an external AAA server. The attributes are mandatory in Access-Request according to the specification, but the PGW would have nothing meaningful to put into the attributes. In practice, these details are left for vendor product specifications. Similarly, as of Release-10, the Delegated-IPv6-Prefix attribute can be used to assign a static delegated IPv6 prefix to a UE. From the AAA server point of view, the UE and the requested APN identification are trivial. The AAA request messages from the PGW always contains the APN in the Called-Station-Id attribute, the Calling-Station-Id attribute contains the Mobile Station International Subscriber Directory Number (MSISDN) of the UE, the 3GPP-IMEISV contains the International Mobile Equipment Identity (IMEI) of the UE, and the 3GPP-IMSI contains the International Mobile Subscriber Identity (IMSI) of the UE. DHCP Infrastructure In a similar manner, a PGW may act as a DHCPv6 client and request an IPv6 prefix for a UE from an external DHCPv6 server. Interestingly, the stateful DHCPv6 procedure as defined in [26] is used and not the DHCPv6 PD procedure [27] as one might expect. The 3GPP specifications are unclear how to populate for example the IAID that would be required to identify each IPv6 address requested for a specific UE. The DUID for the PGW should obviously be the same for all DHCPv6 messages it exchanges. There is some discussion regarding the IAID and 3GPP networks in the context of DHCPv6 PD in [114]. However, there is no unambiguous 3GPP standard about it, thus enabling static IPv6 addressing using DHCPv6 would be more or less vendor specific from the DHCPv6 server provisioning point of view. Furthermore, the 3GPP specifications are silent whether the IID gets conveyed over to the UE in the case of DHCPv6. It is also known that the UE is not mandated to use the received IID for the IPv6 Global Unicast Addresss GUAs it configures. The use of DHCPv6 for static IPv6 addressing falls int