The TIME-WAIT state is a state that all TCP connections enter into when the connection has been closed. The length of time for this state is 240 seconds, which is to allow for any duplicate segments still in the network from the previous connection to expire. The introduction of the CC option in T/TCP allows for the truncation of the TIME-WAIT state. The CC option provides protection against old duplicates being delivered to the wrong incarnation of a given connection.
There are time constraints on this however. Because the CC value from the host is monotonically increasing, there is a possibility that the numbers may wrap around from the client host. A CC value that is the same as some duplicate segments from the previous incarnation may be encountered. As a rule, the truncation can only be performed whenever the duration of the connection is less than the maximum segment lifetime (MSL). The recommended value for the MSL is 120 seconds. As with the original TCP, the host that sends the first FIN is required to remain in the TIME-WAIT state for twice the MSL once the connection is completely closed at both ends. This implies that the TIME-WAIT state with the original TCP is 240 seconds, even though some implementations of TCP have the TIME-WAIT set to 60 seconds. Stevens [18] shows how the TIME-WAIT state for T/TCP may be shortened to 12 seconds.
CC options do have problems when used on networks with high speed connections. This is rarely a problem on older networks, but with FDDI and Gigabit Ethernets becoming more mainstream, the wrapping of the CC value will become more frequent. In this situation, there is a possibility that the CC value may wrap around fast enough for problems to occur [7]. Whereas CC options are not sufficient in certain conditions, the PAWS (Protection Against Wrapped Sequences) [6] option add another layer of security against this problem.