Size of the Acct-Session-Id to be sent to the RADIUS
server. The 32-bit version contains a session serial
number that is incremented by one for each session
number, and is reset to zero upon system reboot. The
64-bit version contains the same session serial
number, but is prefixed with a 32-bit BootEra that is
different each time this system is rebooted. The
combined 64-bit value will be unique for all time for
this system.