w suit during 2013. The only way for operators to get additional IPv4 address space is to purchase it from somebody that is willing to sell it. The oper- ators depend on IP addresses to be able to grow the number of subscribers they serve. A new risk for an operator's business is that the is growth becomes, at least partially, dependent on somebody else being willing to sell their IPv4 addresses. In addition, it is expected that the purchased address blocks will be smaller than the address blocks pro- vided by the Regional Internet Registrys (RIRs). This adds cost to the operator's address management. One strategy for reducing the dependency on the globally routable IPv4 addresses is NAT. Most operators, if not all, already provide private IPv4 addresses to their subscribers, and thus 'NAT' the Internet access. The ratio of connections NATted to a single public, globally routable IPv4 address will only grow in the near future. Using NAT in a big operator's network means that the NAT equipment must be highly scalable and have high capacity. This kind of equipment is not cheap, and thus it adds cost to the operator - both the capital cost of the equipment, and the operational cost of the management of the additional equipment. And all this at the time when the data volumes are increasing. In addition, the increasing ratio of multiplexing of connections will eventually cause some of the connections to fail, and thus may add random failures to the subscribers' service. Many of the major Internet content providers have turned IPv6 on in their services, and most, if not all, modern computing platforms can now use IPv6. This means that when operators turn on IPv6 services, they have to be of at least the same quality as the IPv4 service. Thus, there is little space to train or trial IPv6 anymore. As time goes by, even more traffic will be moving to IPv6 and its importance will only grow. We have explained that the transition to IPv6 is difficult, and needs quite a bit of work. Hence, there is also a lot that can go wron