user perception is therefore obvious. In Europe the EC sees interconnection as a key element in the future competitive environment, allowing new market entrants access to existing end users, on a basis that will encourage increased investment and market growth in the telecommunications sector. Among the main interconnection/interworking success factors are roaming or 'remote service access' including virtual home environment (VHE), representing a wider service access, e2e QoS, e2e security, and a concept that can be called 'always best connected'. Roaming will therefore include roaming between different technologies. The access net- work fragmentation regarding transport technique is counteracted by multi-technology terminals, moving through and between various technological islands. This is a condition for good utilization of the access network. The user services may be identical provided VHE is available. In the good old monopoly days the interconnection issue stressed routing and hierar- chical matters, such as position of international gateways, and mutual accounting between countries. See Figure 15.2. Among important quality matters the distribution of end-to- end loss was most important when the networks were analogue. The transmission plan catered for suitable values, also for national distribution. In the deregulated telecom world the number of actors has increased tremendously. Further, the horizontalization creates possibilities to split the actor network into layers, for example to use the home service environment in a visited area (virtual home envi- ronment, see Section 15.6.1). Also the actors themselves can be split into layers, and/or interconnected in series. As mentioned, QoS and security have become crucial issues. See Figure 15.3. PSTN interwork, between countries Country B Country C Operator B Country A Operator C Operator A International exchange Figure 15.2 The classical interconnect in the monopoly days Interconnection The heterogeneous new telecom tnvironment Interconnected operators SLA*