This article shows you how to change the TCP established value in Linux systems

The default value for the “TCP Established timeout” on a Linux server is 5 days. To bring down this value (in this example, we are changing the value to 5 hours), do the following steps:

Enter the command: echo 18000 > /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_timeout_established

To have this be persistent during reboots do the following:
1. vi /etc/sysctl.conf
2. Enter the line
net.ipv4.netfilter.ip_conntrack_tcp_timeout_established = 18000
The number 18000 represents the number of seconds to change the value to. In this example, we changed the timeout to 5 hours:

60 seconds X 60 minutes x 5 hours = 18000