onger 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 to enterprises. No precise definition of VPN exists. A rough definition is: 'Private (mostly data) traffic utilizing a public network'. Another alternative is 'An encrypted tunnel over unreliable networks'. A third definition is: 'A Virtual Private Network is a private net- work that makes use of the public telecommunications infrastructure, maintaining privacy through the use of tunnelling protocols and security procedures'. The main idea is to create a secure path through the insecure Internet environment by using tunnelling, encryption, keys and other security enablers. Also company-customer information flow should be secure, based on suitable routines. Certainly the customer does not wish that anyone could read his conversation with the company. Yet, high security levels with cumbersome routines might scare off a company's customers. The solution is informing people of the consequences of intruders. By knowing risks, people may better accept security routines. Understanding Changing Telecommunications - Building a Successful Telecom Business 6.7 INTEGRITY AND CONFIDENTIALITY BY ACCESS CONTROL - AUTH