 IID, as that IID is known to be unique on the link. The current IPv6 over 3GPP system is described in depth in 'IPv6 in 3GPP Evolved Packet System (EPS)' RFC 6459 [101]. In 3GPP access to the IID is negotiated during the bearer establishment phase very similarly to PPP, but also other information such as RDNSS addresses and P-CSCF addresses can be negotiated. As the PPP type of PDP context has been dropped from the 3GPP specifications, we will not look in any more depth in this book at how IPv6 is transported over PPP. 3.6.2 IPv6 over Shared Media The cellular link used in 3GPP networks is always a non-shared point-to-point link. Of course, it is very common for mobile handsets to have a shared link type available, when the handsets are attached to non-3GPP accesses, such as home or hotspot WLAN networks. It is also fairly common to have a shared local area link, for example in tethering scenerios, or when a shared medium is used for peer-to-peer communications. The majority of the shared types of links are based on Ethernet technology, for which the IPv6 usage model is defined in RFC 2464 'Transmission of IPv6 Packets over Ethernet Networks' [99]. The most common forms of Ethernet technology are wired and wireless LANs, defined by IEEE 802.3 and 802.11, respectively. The same Ethernet technology, with slight adaptations, is also used by other link layers, such as IEEE 802.15.4 [108] and possibly in Bluetooth Low-Energy as well, for which standardization work is cur- rently ongoing in IETF [116]. The link-layer addresses in Ethernet are 48-bit IEEE 802 addresses. For transmitting IPv6 packets over Ethernet networks, nodes need to find out a link-layer address corresponding to a destination IPv6 address. Please see Section 3.4 for details about how a link-layer address for an IPv6 address is resolved. In the case of multicast addresses, a special Ethernet multicast address of 33 : 33 : XX XX : XX reserved. A function that maps IPv6 multicast addresses to Ethernet multicast addresses works by appending the last 32