ZyXEL P-202H User Guide - Page 117
VPN Screens
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P-202H Plus v2 User's Guide CHAPTER 11 VPN Screens This chapter introduces the VPN web configurator. See the section on logs for information on viewing logs and the appendices for IPSec log descriptions. 11.1 VPN/IPSec Overview Use the screens documented in this chapter to configure rules for VPN connections and manage VPN connections. 11.2 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. 11.2.1 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. 11.2.2 ESP (Encapsulating Security Payload) Protocol The ESP protocol (RFC 2406) provides encryption as well as 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. Chapter 11 VPN Screens 116