net.ipv4.tcp_tw_recycle
nezapínat!tcp_tw_recycle (Boolean; default: disabled; since Linux 2.4)
Enable fast recycling of TIME_WAIT sockets. Enabling this option is not recommended for devices communicating with the general Internet or using NAT (Network Address Translation). Since some NAT gateways pass through IP timestamp values, one IP can appear to have non-increasing timestamps. See RFC 1323 (PAWS), RFC 6191.
(http://man7.org/linux/man-pages/man7/tcp.7.html)