The current Internet has a number of security problems. The Internet lacks effective privacy and effective authentication mechanisms below the application layer. IPv6 remedies these shortcomings by having two integrated options that provide security services. You can use these two options either individually or together to provide differing levels of security to different users. Different user communities have different security needs.
The first option, an extension header called the IPv6 Authentication Header (AH), provides authentication and integrity (without confidentiality) to IPv6 datagrams. The extension is algorithm independent. The extension supports many different authentication techniques. The use of AH is proposed to help ensure interoperability within the worldwide Internet. The use of AH eliminates a significant class of network attacks, including host masquerading attacks. When using source routing with IPv6, the IPv6 authentication header becomes important because of the known risks in IP source routing. Upper-layer protocols and upper-layer services currently lack meaningful protections. However, the placement of the header at the Internet layer helps provide host origin authentication.
The second option, an extension header that is called the IPv6 Encapsulating Security Payload (ESP), provides integrity and confidentiality to IPv6 datagrams. Though simpler than some similar security protocols (for example, SP3D, ISO NLSP), ESP remains flexible and is algorithm independent.
IPv6 Authentication Header and IPv6 Encapsulating Security Payload are features of the new Internet Protocol Security (IPsec). For an overview of IPsec, see Chapter 19, IPsec (Overview). For a description of how you implement IPsec, see Chapter 20, Administering IPsec (Task).