Restoring Stock Firmware via TFTP

Eventually I plan to give this a try myself and attempt a write up of the process. Personally I prefer to use Restoring Stock Firmware without TFTP whenever possible.

In the meantime you can get the required boot files for this process using the process described in Extract Boot Files from Stock Firmware

This post appears to give a good overview of the process: https://www.reddit.com/r/sysadmin/comments/74xoju/how_to_fix_a_buffalo_terastation_tsxel_in_tftp/