Ipsec Architecture; Ipsec And Nat - ZyXEL Communications P-2612HW-F1 User Manual

Chapter 14 VPN

14.9.1 IPSec Architecture

The overall IPSec architecture is shown as follows.
Figure 153 IPSec Architecture
IPSec Algorithms
The ESP (Encapsulating Security Payload) Protocol (RFC 2406) and AH
(Authentication Header) protocol (RFC 2402) describe the packet formats and the
default standards for packet structure (including implementation algorithms).
The Encryption Algorithm describes the use of encryption techniques such as DES
(Data Encryption Standard) and Triple DES algorithms.
The Authentication Algorithms, HMAC-MD5 (RFC 2403) and HMAC-SHA-1 (RFC
2404, provide an authentication mechanism for the AH and ESP protocols.
Key Management
Key management allows you to determine whether to use IKE (ISAKMP) or
manual key configuration in order to set up a VPN.

14.9.2 IPSec and NAT

Read this section if you are running IPSec on a host computer behind the ZyXEL
Device.
NAT is incompatible with the AH protocol in both Transport and Tunnel mode.
An IPSec VPN using the AH protocol digitally signs the outbound packet, both data
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P-2612HW-F1 User's Guide