ution does not provide any form of encryp- tion for data privacy, then this solution is more appropriately called a Vir- tual Network (VN) because nothing is private about the network. Roaming and Wireless VPNs Wireline roaming services and organizations currently provide worldwide gateway-to-gateway voice over IP services, worldwide local-rate corporate dial-up, and PPP-based network access via their clearinghouse services, enabling dynamic VPN setup across a number of providers. Figure 10-6 is a representation of roaming and W-VPN services. Likewise, it will be natural for wireless operators to extend their roaming agreements to include VPN and corporate network access service over the GPRS network. In the future, global roaming and WWW infrastructure could be deployed, together with a widespread availability of mobile IP services. The same infrastructure could eventually be used for both wireline and wireless services. Figure 10-6 Roaming and Wireless VPNs. IPsec Clients IPsec Gateway Server Carrier's Packet Internet Data Network Intranet (any ISP) GTP Connection Security Server IPsec Tunnel, end-to-end Virtual Private Network (VPN) Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. SGSN-to-GGSN (Gn) and GGSN-to-PDN (Gi) Interface Chapter 10 What Makes GPRS VPNs Different? A GPRS VPN shares many requirements with other VPNs. The remote user needs network access comparable to that of on-premise corporate comput- ers. The remote user must be authenticated, possibly by both the access net- work and by the corporation. No eavesdropping should occur on data flowing between the remote user and the corporation, nor should it be pos- sible for the data to be altered by a third party. The presence of VPN users and the infrastructure to support them should not provide a conduit for an intruder to breach the corporate firewall. When a GPRS VPN is being