The value of tIPsecTnlTempPublicTcpMssAdjust specifies the Maximum Segment Size (MSS) for the TCP traffic in an IPsec tunnel which is sent from the public network to the private network. The system may use this value to adjust or insert the MSS option in TCP SYN packet. The TCP MSS adjustment functionality on the public side network is disabled when the following conditions are met. 1) The value of tIPsecTnlTempPublicTcpMssAdjust is '-1' or 2) The values of tIPsecTnlTempPublicTcpMssAdjust and tIPsecTnlTempEncapIpMtu are both '0'. When the system receives a TCP SYN packet from the public network and this packet contains an MSS option, the system replaces the MSS option value with a new MSS when the new MSS is smaller than the MSS option value. When the system receives a TCP SYN packet from the public network and this packet does not contain an MSS option, the system inserts one with a new MSS. The new MSS is calculated based on the following rules. 1) When the value of tIPsecTnlTempPublicTcpMssAdjust is '0' and tIPsecTnlTempEncapIpMtu has a non-zero value, New MSS = tIPsecTnlTempEncapIpMtu - total header size (e.g., encryption, encapsulation, TCP and IP headers) 2) When the value of tIPsecTnlTempPublicTcpMssAdjust is in the range of (512..9000) New MSS = tIPsecTnlTempPublicTcpMssAdjust