ICMPTX (IP-over-ICMP) HOWTO. See the current ICMPTX project home page.
Problem You're sitting in an airport or in a cafe, and people want your money for Internet access. They do allow ICMP traffic, though (i.e., you can ping machines on the Internet). NSTX (IP-over-DNS) HOWTO. Problem The information presented here is obsolete.
Take a look at Iodine. You're sitting in an airport or in a cafe, and people want your money for Internet access.