ZyXEL ISG50-PSTN User Guide - Page 385
AES128, AES192, AES256
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Chapter 24 IPSec VPN Table 126 Configuration > VPN > IPSec VPN > VPN Gateway > Edit (continued) LABEL # Encryption DESCRIPTION This field is a sequential value, and it is not associated with a specific proposal. The sequence of proposals should not affect performance significantly. Select which key size and encryption algorithm to use in the IKE SA. Choices are: DES - a 56-bit key with the DES encryption algorithm 3DES - a 168-bit key with the DES encryption algorithm AES128 - a 128-bit key with the AES encryption algorithm AES192 - a 192-bit key with the AES encryption algorithm AES256 - a 256-bit key with the AES encryption algorithm Authentication The ISG50 and the remote IPSec router must use the same key size and encryption algorithm. Longer keys require more processing power, resulting in increased latency and decreased throughput. Select which hash algorithm to use to authenticate packet data in the IPSec SA. Choices are SHA1 and MD5. SHA1 is generally considered stronger than MD5, but it is also slower. Key Group The remote IPSec router must use the same authentication algorithm. Select which Diffie-Hellman key group (DHx) you want to use for encryption keys. Choices are: DH1 - use a 768-bit random number DH2 - use a 1024-bit random number DH5 - use a 1536-bit random number NAT Traversal The longer the key, the more secure the encryption, but also the longer it takes to encrypt and decrypt information. Both routers must use the same DH key group. Select this if any of these conditions are satisfied. Dead Peer Detection (DPD) • This IKE SA might be used to negotiate IPSec SAs that use ESP as the active protocol. • There are one or more NAT routers between the ISG50 and remote IPSec router, and these routers do not support IPSec pass-thru or a similar feature. The remote IPSec router must also enable NAT traversal, and the NAT routers have to forward packets with UDP port 500 and UDP 4500 headers unchanged. Select this check box if you want the ISG50 to make sure the remote IPSec router is there before it transmits data through the IKE SA. The remote IPSec router must support DPD. If there has been no traffic for at least 15 seconds, the ISG50 sends a message to the remote IPSec router. If the remote IPSec router responds, the ISG50 transmits the data. If the remote IPSec router does not respond, the ISG50 shuts down the IKE SA. Extended Authentication If the remote IPSec router does not support DPD, see if you can use the VPN connection connectivity check (see Section 24.2.1 on page 371). When multiple IPSec routers use the same VPN tunnel to connect to a single VPN tunnel (telecommuters sharing a tunnel for example), use extended authentication to enforce a user name and password check. This way even though they all know the VPN tunnel's security settings, each still has to provide a unique user name and password. ISG50 User's Guide 385