This report is one of the best at explaining what open access is and why it is important.

At a high level, everyone understands what it means for a network to be open: (1) whatever else it might do, the network offers a pure “transmission” service, so that users can freely communicate with each other; (2) users can connect any devices they want, as long as they don’t harm the network; (3) the network connects to other networks; and (4) the network doesn’t discriminate among users or among the services, information, and applications users want to provide to each other. None of these points should be controversial. The concept of open networks is at least 40 years old in the US. The FCC’s seminal 1968 Carterphone decision held that a network operator may not forbid the use of devices on the network that benefit the user and do not harm the network itself. A decade later the FCC established its equipment registration program requiring interfaces to the telephone network to be standardized and fully disclosed.