 The last method implies assigning a special country code ("878," defining a "world wide UPT community") to UPT users who want to roam world wide. The network accepting a call to an UPT number must translate this number to the terminal identity, called UPT global title (UPTGT), where the UPT user will take the call. The choice of the term "global title" may seem odd when the terminal is connected to a fixed access, because, in that case, it is used by the network as an NA. However, UPT also works over mobile terminals, in which case the UPTGT is actually a global title. The fact that the UPT user can access the network from a large number of accesses, as if using one's own fixed access, requires certain new procedures, to be used by UPT users and to be realized in the network. The basic procedures are: To be reachable, the UPT user's location must always be registered in the net- work. If the user wants to take and make his call from a fixed access, he must exercise a registration procedure, telling his UPT operator the network address of the access he will use. If the user wants to take and make his call from, e.g., a GSM mobile, he must give the MSISDN of that terminal. These procedures are equivalent to the location update procedures in mobile networks, only that they are not made automatically. 3 Node Structures Whether the UPT user receives a call, makes a call, want to register his wherea- bouts or change his service profile, he must exercise an authentication procedure to avoid frauds, i.e., somebody else using his UPT number for getting services from the network. Charging an UPT user who makes a call to a non-UPT user is as any other call. However, when somebody makes a call to an UPT user, the same problem as in mobile networks arises: if I call somebody in my own cellular network I do not expect to have to pay extra for the fact that he might take the call on the other side of the earth. At least I want to be made aware of that fact, before I decide to go through with the call. Thus, UPT requires more a