 is an example of mesh topology. 5.2.4 Scalability Concerns The transition/migration technology selection should pay close attention to various scalability concerns. We have already mentioned possible unwanted core network side translation state increase in Section 5.2.1 as one of the scalability concerns. However, scalability is not only about the processing and maintaining the translation state. The following other scalability affecting concerns should also be considered: Does the transition/migration solution have wasteful requirements on the address space? It is common that transition/migration solutions make use of embedding all kinds of transition specific information into the IPv6 address. For example, a typical 6RD deploy- ment requires at minimum /32 IPv6 prefix to be dedicated just for transition purposes for each 6RD domain that the operator deploys. It is SO much easier, from a management and rollout point of view, to embed the whole IPv4 address into the 6RD delegated prefix rather than starting to design prefixes and routing based on the scattered IPv4 subnets. The popularity of 6RD even affected the IPv6 initial allocation and assign- ment size policies at Regional Internet Registry (RIR) level [18]. Another example is 464XLAT [19], which basically promotes assignment of two /64 IPv6 prefixes for each UE (one for native IPv6 traffic and the other for the translated IPv6 traffic, though it can also work with a single /64 prefix). While one can argue that there are enough IPv6 addresses for all possible imaginable uses, the wasteful IPv6 address use might come back to haunt us in few years' time. Does the transition/migration solution have an impact on the external and/or internal routing infrastructure? For example, a transition solution might require advertising anycast routes or host routes in the Interior Gateway Protocol (IGP). What kind of logging impact does the transition/migration solution have? The solution might not have a good way to deterministically build, for example, the translation s