In order to limit unwanted Internet usages (games, videos, chats), many employers only allow web browsing in office, that is technically speaking, they only open 80 and 443 on TCP.
But you still can use openVPN to unblock all blocked sites, AND… blocked usages! That means if you normally cannot use your favorite IM to chat with your girlfriends or watch TV shows online in office now you can do these with openVPN:-)
If openVPN uses 443 TCP, it cannot be blocked since all secured sites starting with https (like all banks) use the same port and protocol.
That means if ISPs, employers or schools try to shut down 443 on TCP, they will also block all secured sites.
Breakwall VPN offers best openVPN solution: 4 ports on both TCP and UDP (faster) with 12 servers in Japan, US and UK.