South Korea Rail offers wifi access points for each two carts, but they block users very quickly, after around 5 minutes of 360p streaming video.

Their blocking mechanism is implemented as MAC address filtering and they pass your MAC address in as a url parameter at the 'login' page.

So to get unlimited wifi on Korea Rail, every time they block you simply login again with a modified MAC address parameter in the URL, eg:

http://ems.ktxinternet.net/login/?gw_address=192.168.17.1&gw_port=3553&gw_id=08-13-14&url=http%3A//google.com/&mac=XX:XX:XX:XX:XX:XX