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ZyWALL 2 Series User’s Guide
VPN Screens
14-1
Chapter 14
VPN Screens
This chapter introduces the VPN Web configurator. See the Logs chapter for information on
viewing logs and the appendix for IPSec log descriptions.
14.1 VPN/IPSec Overview
Use the screens documented in this chapter to configuring and managing a VPN connection.
14.2 IPSec Algorithms
The
ESP
and
AH
protocols are necessary to create a Security Association (SA), the foundation of an IPSec
VPN. An SA is built from the authentication provided by the
AH
and
ESP
protocols. The primary function
of key management is to establish and maintain the SA between systems. Once the SA is established, the
transport of data may commence.
14.2.1 AH (Authentication Header) Protocol
AH
protocol (RFC 2402) was designed for integrity, authentication, sequence integrity (replay resistance),
and non-repudiation but not for confidentiality, for which the
ESP
was designed.
In applications where confidentiality is not required or not sanctioned by government encryption restrictions,
an
AH
can be employed to ensure integrity. This type of implementation does not protect the information
from dissemination but will allow for verification of the integrity of the information and authentication of the
originator.
14.2.2 ESP (Encapsulating Security Payload) Protocol
The
ESP
protocol (RFC 2406) provides encryption as well as some of the services offered by
AH
.
ESP
authenticating properties are limited compared to the
AH
due to the non-inclusion of the IP header
information during the authentication process. However,
ESP
is sufficient if only the upper layer protocols
need to be authenticated.
An added feature of the
ESP
is payload padding, which further protects communications by concealing the
size of the packet being transmitted.