参考：
[1] http://bbs.chinaunix.net/thread-2318039-1-1.html
net.core.netdev_max_backlog = 1000
TCP KeepAlive
net.ipv4.tcp_keepalive_time = 7200
net.ipv4.tcp_keepalive_probes = 9
net.ipv4.tcp_keepalive_intvl = 75
Linux 网络（连接）相关参数作用,布布扣,bubuko.com
Linux 网络（连接）相关参数作用
原文：http://www.cnblogs.com/lailailai/p/3911245.html
