For FTP ... this was disussed just the other day for another member.
Look here: http://computerforums.org/showthread.php?t=76011
About the YouTube video. He's created a bat file that tells him what the non-authortative ip address(s) are for a blocked site. YouTube has their front IP Address but has several servers that host their video files. If a school only knows the DNS name of www.youtube.com
... they're going to point directly to the main host server / main host ip address. It might not be aware of all the additional servers behind that main host server/ip address. Therefore ... all the other IP addresses will be available to connect to, but you'd need to know the numbered IP addresses, because the dns address of www.youtube.com/
.... is blocked. Make sense? Most school admins worth their salt ... will have all command.exe access blocked. And I'm not criticizing the small town school districts that can't afford a true network admin, but they're at the most risk.
BTW ... what is described in the youtube video as proxy is not right. It's just a tool to "lookup" additional (non-authoritative) IP addresses of a website ... thus the nslookup command.