gw/so_keepalive is a SAP Parameter attribute which is used to control Enable/disable socket option SO_KEEPALIVE information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
Parameter to activate the socket option KEEPALIVE for the network
connections. Only new connections are affected when this option is
activated or deactivated. You can activate or deactivate this option for
existing connections using the gateway monitor (SMGW).
See SAP Parameter Documentation for full SAP documentation for this profile parameter.