关于Slow HTTP Denial of Service Attack slowhttptest的几种慢攻击DOS原理
http://www.myhack58.com/Article/60/sort096/2012/35008.htm
How To Mitigate Slow HTTP DoS Attacks in Apache HTTP Server
http://www.acunetix.com/blog/web-security-zone/articles/slow-http-dos-attacks-mitigate-apache-http-server/
Apache Module mod_reqtimeout
http://httpd.apache.org/docs/2.2/mod/mod_reqtimeout.html