d by different names and structures of identifiers for this kind of networks. For example, in GSM, the correspondence to a GT is called mobile station ISDN number (MSISDN), while an NA (for routing purposes) is assigned temporarily to a termi- nal (when involved in a call) as a mobile station roaming number (MSRN). Both identifiers are however part of the same general numbering system for telephony systems (according to ITU-T E. 164). Thus, the independence between numbering system for GTs and NAs that we assumed for packet-switching network systems is not entirely implemented. Personal mobility. In fixed access networks (PSTN/ISDN), terminals are fixed, but users are roaming around. Thus, a global route (if the network supports something like that) exists between users of network terminals (normally persons). Persons are inherently mobile. Traditionally, however, PSTN/ISDN operators are not concerned with who uses a terminal (i.e., a telephone). They only see the person who subscribes to the fixed access, which is the one who pays the bill, no matter who used the telephone. In that sense, PSTN/ISDN has always supported mobility without using any GT (for persons). This way of providing services has, however, some awkward consequences as well: Since the network only handles NAs (i.e., telephone numbers), it implies that if I move my telephone to another access, I must normally accept another NA, since otherwise the routing strategy (reflected by the number structure) would break down. It may take some time before all my friends find me again. A user who is not close to the access subscribed to cannot be reached. Fixed access telephony networks try to overcome this problem by diverse redirect and voice mail box services. Services are bound to accesses, i.e., to the person who subscribes to the access. Within the network, every access is associated to a particular service profile, which defines which services are subscribed to over that access. Thus, if I use an access other than my own, I am constrained to the serv