s in fact fairly tricky. One reason is that the service explosion requires multimedia and multi-service traffic with different requirements regarding QoS and security. Another reason is a considerable possible layering in the BD area. 4.4.1 EXAMPLES OF INDIVIDUAL ROLES A number of possible value chains have been presented in the literature. The area of roles including terminology and business relationships is not yet stable. Some common features are: the convergence between media industry and telecom demands, as a minimum, 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 