m, a content provider role, a network operator role, and a role in between, to connect the end user to the content; the Internet service provider (ISP) or the wireless Internet service provider (WISP) using the WLAN technique (explained in Chapter 13). See Figures 4.18 and 4.19. Charging and security are important ISP tasks. The connectivity or communication part of the chain can be split for example according to the reference model in Figure 4.16. The number of competing actors in the access role increases. In other parts mergers are expected. Apart from the access part the reference network shows three networks with associ- ated roles: a backbone connectivity network, operated by carriers, in its turn carrying; core networks (such as a GPRS or UMTS core network, a national PSTN/ISDN core network, or a network of a regional or global operator) and IP service networks; the service network provider role connects a large number of servers to an IP network to link the content residing in servers to the clients in a client-server or peer-to-peer relationship (application servers, application support servers, service capability servers, IP infrastructure servers). Understanding Changing Telecommunications - Building a Successful Telecom Business Authentication server Access server PSTN/ Modem Modem Firewall Modem Terminal server server (x2) Modem Ethernet Mail, news www, FTP Ethernet servers, etc. Router Company access router and firewall Internet Figure 4.18 The initial role of the ISP illustrated by an example of point-of-presence configuration (the access server is sometimes denoted NAS, network access server) Wireless Internet service provider (WISP) WISP service - fast Internet access in public place Office Hotel & Conference Mobility Shopping malls Airport Figure 4.19 A WISP offers Internet access at hot spots In networks with network-centric intelligence there are normally supplementary ser- vices, which include IN services, and information-type value-added services ('Telephone Bank'). These information-type se