ISITED Network Network Network Network Services Services Services Services Session Session Session Session control control control control Mobility Mobility Mobility Mobility Connectivity Connectivity Connectivity Connectivity Figure 15.10 Fetching and returning services The services are offered by the home environment service provider or an associated 'HE-VASP' (home environment-value-added service provider). Figure 15.9 shows how the home environment services are reached schematically. To a significant extent VHE provides visited network independence. The relationship between visited and home network can be more basic (network oriented). This approach minimizes the restrictions on service deployment in the home network. The end user depends only on the own service provider, not the 'foreign' (visited network) one, regarding service profiles, pin codes etc. Global credit card service is also solved by VHE. VHE will protect privacy issues. The session also includes the return communication. Figure 15.10 provides both direc- tions for a mobile subscriber. 15.7 QoS INTERWORKING See Figure 15.11 that illustrates the situation. Many enablers for QoS are available (see Chapter 7). In the connectivity part. RSVP, Diffserv, MPLS and over-dimensioning are common. In the terminals and servers protocols for QoS such as CC/TP, RTP, RTSP and RTCP are available. What will the end-to-end QoS look like? Understanding Changing Telecommunications - Building a Successful Telecom Business End-to-end connectivity? I use IP I use | use over ATM! DiffServ! MPLS! RSVP! Access Access domain domain domain domain Inter-domain Inter-domain Inter-domain border signalling border signalling border signalling There is no shortage of possible approaches-and they are all in use! The problem - How to guarantee end-to-end service with the required QoS across multiple networks using incompatible implementations [a subject of international work] Figure 15.11 QoS elements and some alternatives What is required is obviously an end-to-end operation con