KLIPS
KLIPS: "kernel IPsec support". This is the kernel portion of FreeS/WAN, Openswan and Strongswan. Not to be confused with NETKEY (aka 26sec), the kernel IPsec implementation included with kernel 2.6, which is also supported by recent versions of FreeS/WAN, Openswan and Strongswan.
KLIPS:"kernel IPsec support".这是FreeS/WAN, Openswan and Strongswan的核心部分。不要和NETKEY混淆，kernel IPsec implementation被包含在LINUX内核2.6里，它被最新版本的FreeS/WAN, Openswan 和 Strongswan支持。
PS：KLIPS是在LINUX内核里，是对IPSEC的支持，要在内核里开启该选项。