 data that is independent of the key generation technique, encryption algorithm, and authentication mechanism. One of the major benefits of the IPSec efforts is that the standardized packet structure and SA within the IPSec standard will facilitate third- party VPN solutions that interoperate at the data transmission level. How- ever, it does not provide an automatic mechanism to exchange the encryption and data authentication keys needed to establish the encrypted 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 SGSN-to-GGSN (G) and GGSN-to-PDN (G) Interface session, which introduces the second major benefit of the IPSec standard: key management infrastructure or Public Key Infrastructure (PKI). The IPSec working group is in the development and adoption stages of a standardized key management mechanism that enables safe and secure negotiation, distribution, and storage of encryption and authentication keys. A standardized packet structure and key management mechanism will facilitate fully interoperable third-party VPN solutions. Other VPN technologies that are being proposed or implemented as alternatives to the IPSec standard are not true IPSec standards at all. Instead, they are encapsulation protocols that tunnel higher-level protocols into link-layer protocols. Security The key technologies that comprise the security component of a VPN are Access control to guarantee the security of network connections Encryption to protect the privacy of data Authentication to verify the user's identity as well as the integrity of the data Network security is an extremely important issue for network adminis- trators and one that must be addressed in remote access services. Integrated at the VPN point of access, user authentication establishes the identity of the person using the VPN node. This is because 