Allied Telesis AT-S63 - Manual (Page 59)

AT-S63 Management Software Menus Interface User’s Guide
Section I: Basic Features 59
Caution
The switch does not forward traffic while it reloads its operating
software, a process that takes approximately 20 seconds to
complete. Some packet traffic may be lost. After the switch finishes
rebooting, you must reestablish your management session if you
want to continue managing the unit.