ce network is today. Casual e-mail is considered less risky, but at least business e-mail should be protected. Voice over IP may introduce risks for other services and needs protection against reavesdropping/wiretapping. In today's workplace there is a need to provide access to employees even when they are outside the office. This need arises first for the 'road-warrior' employees such as a sales persons or installation teams, but also for accommodating home workers and 'day- extenders'. Traditionally, such access has been provided with dial-in connections to a corporate network access server (NAS). See for example Figures 6.15 and 6.16. This approach has, however, several drawbacks: The corporation has to invest in the installation and management of the NAS. While easy and inexpensive from the same geographical area as the corporate offices dial-in access from overseas locations may be prohibitively expensive. The introduction of new access technologies such as digital subscriber line (DSL or xDSL, such as ADSL) with higher bandwidth but shorter distances is making the corporate-owned NAS approach no longer possible or necessary. For these reasons corporations are moving towards the model where local access is provided by for example the DSL provider and connectivity to the corporate Intranet is provided through IP networks. This provides substantial benefits to corporations in terms of how fast, easily and flexibly they can provide remote access. The solution for secure applications has initially been building a private network, but with the wide-spread use and availability of the Internet it is of large economic interest Security Modem Modem Home PC Modem Internet Modem Company network RADIUS' Figure 6.15 RADIUS dial-in Network access servers RADIUS Users server Figure 6.16 A RADIUS connection. The RADIUS position can be seen in Figure 6.16 to introduce security there. The main secured Internet service is called virtual private network (VPN). It is tailored for wide area enterprise networking and remote access