This read-write value, in seconds, is the guestVlanPeriod timer the switch uses before assigning a port to its Guest VLAN following an unauthenticated state. An admin cares because it controls how quickly a client without a supplicant gets shifted to guest access versus how long a legitimate client is given to complete 802.1x authentication first. For example, the default of 90 seconds gives a PC 90 seconds to authenticate before its port is placed into the Guest VLAN.