System clock mode, which range from 1 to 3, stands for default mode, timestamp mode and auxiliary clock mode respectively. It allows network administrator to change system clock mechanism by setting this variable. For instance, if administrator intend to use auxiliary clock as system timer, whom is required to set this variable's value as 3, i.e SYSCLK_AUX. All supported values of this variable are listed as follows: 1: SYSCLK_DFLT default mode 2: SYSCLK_TS timestamp mode 3: SYSCLK_AUX auxiliary clock mode.