- the access to the DNS server, and the DNS records. Obviously, if the network is transitioned to IPv6 the network elements will contact the DNS server on IPv6 as well. Hence, the DNS server needs to be IPv6 capable. In addition, when network elements are configured with IPv6 addresses, the DNS records pointing to those nodes have to have the related AAAA records added. Operator Service Network Here we call the network that connects the UE to the operator services, and to the Internet, the operator service network. Sometimes there may actually be different networks, and hence different APNs, for the operator's own services and for the Internet connectivity. The transition process does not really change even if there are one or multiple networks, or network segments. The only difference is that if some services are in their own networks behind a separate APN, the networks can be transitioned at different times. This may be useful if the operator's own services are difficult to transition when they have been built perhaps on platforms that are not upgradable. However, this also means that multiple networks have to be upgraded instead of just one. The upgrading of the network itself, including the switches and routers, the DNS, and the operations and management infrastructure, follows the same lines as the transition of the operator's infrastructure network, or any other IP network. The switches and routers have to be IPv6 capable to transport IPv6 packets. The IPv6 access to the DNS servers has to be added - and it has to be ensured that the DNS servers do support queries over IPv6, configuring the infrastructure providing the protocol configuration options to the UE to include the IPv6 address of the DNS servers, and obviously connecting the DNS server to the operator's IPv6 network. As in the operator's internal network, the operation and management infrastructure has to be upgraded to support configuring and monitoring of the IPv6 network and its nodes. In Section 4.4, we described the address allocation support