Administrator Guide

190 Web Tools Administrator’s Guide
53-1002756-01
IPsec concepts
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FIGURE 41 Transport mode and tunnel mode comparison
IPsec header options
IPsec adds headers to an IP datagram to enable authentication and privacy. There are two options:
• Authentication Header (AH)
• Encapsulating Security Payload (ESP)
Authentication Header
AH can be used to authenticate a data stream, but does not provide encryption needed for privacy.
The AH contains a message authentication code (MAC). The MAC is created by a hash algorithm
calculation. The MAC is transmitted in an IP datagram. The same hash algorithm is then used by
the receiver to verify the integrity of the packet. AH can be used in either transport mode or tunnel
mode, as shown in Figure 42.
FIGURE 42 AH header in transport mode and tunnel mode