, X.25, frame relay and ATM to IP-VPN tunnels. The IP-VPN tariff is based on IP with no distance dependent fee, as opposed to frame relay and leased lines. The solution will be cheaper, global and flexible. VPN is mainly presented in Chapter 7. The FR/ATM/IP-VPN operators could expand their business and incorporate telephony. A traditional PBX could be replaced by an IP-PBX or an IP-Centrex solution (Case 7). See Figure 8.13. Service Implementation Operator located IP- PBX or IP Centrex Figure 8.13 IP-PBX is located at the CPE (not shown) or outsourced as operator located and managed, or as an IP-Centrex Another IP voice solution is related to the backbone network: voice trunking, defined in Appendix 3, Objectives. The operator might also take care of modem traffic in the PLMN/PSTN/ISDN by means of NAS connections (Case 8). This is called Internet offload or data offload and is also defined in Appendix 3, Objectives. WLAN traffic (Case 2) and xDSL IP traffic (Case 4 and 6) might be connected with or without IP telephony. The expansion into voice traffic requires equipment such as gatekeepers and voice gateways. In fact, the development could end up in the target network with IP multimedia. See Figure 8.14. The WLAN operation for Internet and intranet access (Case 2) can also expand or integrate with other networks, such as 3 G. See Chapter 15. The incumbent (fixed) operator (Case 3) has clear ambitions and possibilities to offer all types of services in the list. It is true that for example MMS is seen as a mobile service, but the fixed network has a long tradition in messaging. The incumbent operator has for some time been in the forefront regarding migration of the backbone to packet mode (IP, ATM, MPLS). Considering that voice is the main service, a telephony server (TeS in Figure 8.14) is a key component in the network. An example of a migration scenario is given in Appendix The xDSL solutions (Case 4) may be based on ATM or IP as transfer mode. They will be connected to the packet backbone accordingly. The m