Draytek Vigor2920 Series User Manual page 250

Phase 2: negotiation IPSec security methods including Authentication Header (AH) or
Encapsulating Security Payload (ESP) for the following IKE exchange and mutual
examination of the secure tunnel establishment.
There are two encapsulation methods used in IPSec, Transport and Tunnel. The Transport
mode will add the AH/ESP payload and use original IP header to encapsulate the data payload
only. It can just apply to local packet, e.g., L2TP over IPSec. The Tunnel mode will not only
add the AH/ESP payload but also use a new IP header (Tunneled IP header) to encapsulate the
whole original IP packet.
Authentication Header (AH) provides data authentication and integrity for IP packets passed
between VPN peers. This is achieved by a keyed one-way hash function to the packet to create
a message digest. This digest will be put in the AH and transmitted along with packets. On the
receiving side, the peer will perform the same one-way hash on the packet and compare the
value with the one in the AH it receives.
Encapsulating Security Payload (ESP) is a security protocol that provides data confidentiality
and protection with optional authentication and replay detection service.
Available settings are explained as follows:
Item
IKE Authentication
Method
IPSec Security Method
After finishing all the settings here, please click OK to save the configuration.
Vigor2920 Series User's Guide
Description
This usually applies to those are remote dial-in user or node
(LAN-to-LAN) which uses dynamic IP address and
IPSec-related VPN connections such as L2TP over IPSec and
IPSec tunnel.
Pre-Shared Key -Currently only support Pre-Shared Key
authentication.
Pre-Shared Key- Specify a key for IKE authentication
Confirm Pre-Shared Key- Retype the characters to confirm
the pre-shared key.
Medium - Authentication Header (AH) means data will be
authenticated, but not be encrypted. By default, this option is
active.
High - Encapsulating Security Payload (ESP) means payload
(data) will be encrypted and authenticated. You may select
encryption algorithm from Data Encryption Standard (DES),
Triple DES (3DES), and AES.
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