e Network (PLMN)). When an operator turns IPv6 on as an end user service, it does not only expose its own network to IPv6, but also possibly all its roaming partners' networks. The subscribers expect that the services they are getting in their home network will also be available when they are roaming in different networks. If nothing else, they will try to use the same service also when roaming. This can cause surprises both for the user and for the network in which the user is roaming. If the service is not available, the user experience may be disappointing, which by itself is already undesirable. However, the user may also call the operator's support line causing additional costs or, depending the level of disappointment, may even cause them to change operators. On the other hand, the visiting network might be a little surprised at the IPv6 traffic running on their network. This causes IPv6 addresses to be present in the visiting operator's logs, billing records, and other records that the operator might collect for different purposes. This traffic can either cause warning bells to ring as the IPv6 traffic may be considered to be an anomaly, or make the unsuspecting backend software such as billing and charging software behave in an undefined way, or even fail completely. Obviously, it is every operator's own responsibility to make sure the network is well prepared and protected when IPv6 is turned on by the operator itself or by a roaming partner, even if the operator itself has not yet turned IPv6 services on. With roaming, the situation is similar on the transport plane. When an operator turns on IPv6 in its transport plane network, the change can be visible to the roaming partners as well. The DNS queries for the network elements resolve to both A and AAAA records, and the GTP signaling may start to contain IPv6 addresses. The operators will have to be ready for this, and make sure that at least a roaming partner's transition does not cause adverse effects on the operator's own network, or vice versa. Surp