Maximum segment lifetime or MSL is the time a TCP segment can exist in the internetwork system. It was defined in 1981 to be . The specification calls for this value to be used for the "time-wait" interval, the minimum time a system must keep the socket in the state before designating the socket closed, thus preventing the socket from being re-used before that interval. Values in various operating systems The command that can be used on Solaris systems (prior to v11) to determine the time-wait interval is: ndd -get /dev/tcp tcp_time_wait_interval 60000 (60 seconds) is a common value. On FreeBSD systems this description and value can be checked by the command sysctl: sysctl -d net.inet.tcp.msl sysctl net.inet.tcp.msl which gets the result: net.inet.tcp.msl: Maximum segment lifetime net.inet.tcp.msl: 30000 In Linux, the time-wait interval is defined by the , hard-coded as 60 seconds. Linux implements several possible optimizations to shorten the state through recycling, down to a minimum of 3.5s in recent kernels. References Transmission Control Protocol