防御Dos攻击

按照之前看过的一篇文章我对tcpip协议管理进行了一点设置，希望能对缓解网站的访问压力有效。

该文章我已经拷贝下来了，就在以下链接：
http://www.cfaq.com.cn/html/64/n-64.html

我的详细操作如下：

一，使用ssh登录linux as4后：
# sysctl -a | grep syn
net.ipv6.conf.default.max_desync_factor = 600
net.ipv6.conf.all.max_desync_factor = 600
net.ipv6.conf.eth0.max_desync_factor = 600
net.ipv6.conf.lo.max_desync_factor = 600
net.ipv4.tcp_max_syn_backlog = 1024
net.ipv4.tcp_syncookies = 0
net.ipv4.tcp_synack_retries = 5
net.ipv4.tcp_syn_retries = 5
fs.quota.syncs = 18

# sysctl -w net.ipv4.tcp_max_syn_backlog=2048
net.ipv4.tcp_max_syn_backlog = 2048
# sysctl -w net.ipv4.tcp_syncookies=1
net.ipv4.tcp_syncookies = 1
# sysctl -w net.ipv4.tcp_synack_retries=3
net.ipv4.tcp_synack_retries = 3
# sysctl -w net.ipv4.tcp_syn_retries=3
net.ipv4.tcp_syn_retries = 3

二、在/etc/rc.d/rc.loacl文件中添加下面四行

sysctl -w net.ipv4.tcp_max_syn_backlog=2048
sysctl -w net.ipv4.tcp_syncookies=1
sysctl -w net.ipv4.tcp_synack_retries=3
sysctl -w net.ipv4.tcp_syn_retries=3