ted many more addresses for various protocols than those listed here, and it is not feasible to include a full list here. The list of IANA's allocations is available at http://www.iana.org/assignments/ipv6-multicast-addresses/ipv6-multicast-addresses.xml. Multicast Router Discovery In some network deployments, layer two multicast-aware switches need to know link-layer addresses of multicast routers. They can find them via utilization of layer-two Multicast Router Solicitation and Multicast Router Advertisement messages [55]. This technology is not relevant in 3GPP networks and hence we do not look into that in any more detail. Solicited-node Multicast Address Formation Solicited-node multicast address is used when a node performs Duplicate Address Detection (DAD) (see Section 3.4.7) and link-layer address resolution (see Section 3.4.4). Figure 3.13 illustrates how a Solicited-node multicast address is created from a 128-bit IPv6 address by picking the 24 lowest bits and appending them to the ff02 1: ff00 : /104 prefix. 3.3 Internet Control Message Protocol Version 6 One of the most important components of the IPv6 protocol suite is ICMPv6 [56]. The ICMPv6 protocol is maybe best known for its use for 'pinging' other nodes for reachability by using ICMPv6 Echo Request and Reply messages, and for its ability to indicate failures in packet delivery to the originating node, such as 'destination unreachable'. 104 bits 24 bits ff02:0:0:0:0:1:ff0o::/104 XX:XXXX lower 24 bits prefix Interface Identifier (IID) 128 bits Figure 3.13 Solicited-Node IPv6 multicast address format. Deploying IPv6 in 3GPP Networks However, in IPv6 ICMPv6 plays a much more significant role than Internet Control Message Protocol version 4 (ICMPv4) does in IPv4. This is mostly due to the use of ICMPv6 for the IPv6 Neighbor Discovery protocol (see Section 3.4). ICMPv6 does not have any automated retransmission mechanisms in case of lost packets, and hence, for example, ICMPv6 errors may not always be received even if they are sent. The protocols that