DIA is more about the business terms of the Internet connection and not the technology or delivery method (fiber optic, DSL, Cable, wireless, etc.). Dedicated Internet Access means that the specified amount of bandwidth sold has been carved out and dedicated for your use.
DIA service performs consistently day in and day out, and has guaranteed minimums and uptime. DIA service is sold as a rated speed, not an up to speed. Dedicated internet access is like having your own personal lane on the Information Superhighway as opposed to sharing the same traffic lanes as everyone else.