KP) is a special reserved prefix: 64: ff9b: : /96. It can be used within an operator's own network instead of the NSP. The WKP has certain limitations such as that it cannot be advertised into the global Internet routing system. The NSP is a 'normal' IPv6 prefix that the operator has reserved for NAT64 translation purposes. Whether the NSP is a Unique Local Address (ULA) or a globally routable prefix is for the operator to decide. Deploying IPv6 in 3GPP Networks DNS64 NAT64 Internet 'AAAA' RR query for 'www.nsn.com' 'AAAA' RR query for 'www.nsn.com' No 'AAAA' provisioned Response without 'AAAA' RR in answer 'A' RR query for "www.nsn.com" 'A' Response: 50.19.98.143 Synthesize 'AAAA' RR using NSP-based Pref64::/96 2001:1bc8:101:f190:200:5e00::/96 'AAAA' Response: 2001:1bc8:101:f190:200:5e00:3213:628f ICMPv6 Echo Request: src: 2001:1bc8:101:f192:ba27:ebff:fecc:a78e dst: 2001:1bc8:101:f190:200:5e00:3213:628f Pref64::/96 gets routed towards NAT64 NAT IPv6 -> IPv4: src to public IPv4:192.0.2.2, dst to public IPv4: 50.19.98.143 ICMPv4 Echo Request src: 192.0.2.2, dst: 50.19.98.143 ICMPv4 Echo Reply src: 50.19.98.143, dst: 192.0.2.2 NAT back IPv4 -> IPv6: src to IPv6: 2001:1bc8:101:f190:200:5e00:3213:628f dst to IPv6: 2001:1bc8:101:f192:ba27:ebff:fecc:a78e ICMPv6 Echo Reply: src: :001:1bc8:101:f190:200:5e00:3213:628f dst: 2001:1bc8:101:f192:ba27:ebff:fecc:a78e Figure 5.2 An example of DNS64 and a NAT64 operation. IPv4-mapped IPv6 addresses are further divided into two categories: IPv4-converted IPv6 addresses: IPv6 addresses used to represent IPv4 nodes in an IPv6 network. These would, for example, be the synthesized IPv6 addresses received from DNS64. IPv4-translatable IPv6 addresses: IPv6 addresses assigned to IPv6 nodes for use with stateless translation. Nodes with IPv4-translatable IPv6 addresses are reachable from the IPv4 internet side (at least in theory). For each IPv4-translatable IPv6 address IPv6 Transition Mechanisms for 3GPP Networks 128 bits Pref64/32 v4 (32) suffix Pref64/40 v4 (24) suffix Pref64/48 v4 (1