rivacy, see also Section 6.9.1) at the application level and link layer encryption. Link layer encryption could for example be used for leased lines and frame relay or ATM WANs. Terminal Security layering, example Server Other network(s) Browsers encryption Applications proxy filtering Content Attack Network user Authentication, authorization, name resolution, charging Attack Communication control Session establishment with e2e security Attack Connectivity Filtering, tunneling Attack User information flow Figure 6.12 A two-dimensional view Understanding Changing Telecommunications - Building a Successful Telecom Business (Remote access) HTTP, etc. WSP, etc. Term, etc. HTTP, FTP etc. See tunneling TLS/SSL See integrity IP security Figure 6.13 A layered view with four protection methods indicated Encryption, in order to achieve confidentiality protection, can be used at all layers. Regarding protection at the link and physical layers, solutions are normally not continuous end to end, because of the link-by-link architecture. In GSM, for example, the physical layer is encrypted between the mobile and the base station. In WLAN according to IEEE 802.11 layers 1 and 2 are used for encryption in a standard called wired equivalent privacy (WEP). Since the IP protocol is normally used end to end an IP layer encryption can/should be maintained all the way. A common layer 3 encryption is part of IPsec, commonly used for IP-VPN. Encryption at higher layers increases the security even further, but has the drawback that the applications need individual encryption. An example is secure socket layer (SSL) at layer 4 that can protect HTTP web traffic. The layered view is applicable to many standards in the new network. 'Ordinary' standards for content to user communication are covered in Chapter 3. Service and business-oriented standards are explained in Chapter 5, security standards in Chapter 6, QoS standards in Chapter 7 and specific enabler standards in Chapter 8. 6.6.3 THE FUNCTIONAL (FP) VIEW Security for Network Management