System time is maintained by the software. When a switch is initialized, the system time is set from a hardware time clock (system calendar) in the switch.
An accurate system clock is important to maintain, especially when you need to compare the output of logging and debugging features. A switch timestamps these messages, giving you a frame of reference.
System time is maintained as coordinated universal time (UTC, also known as Greenwich mean time,GMT). The format of time as it is displayed can be configured with operating system commands.
System time can be set manually or by Network Time Protocol (NTP). In addition, the hardware time clock in a switch can be updated by NTP if desired.
NTP uses a concept of stratum to determine ...