This is a sub-dimension and not a major one, because it can be derived out of Technology of Education and Goals of education. If the goal of education is imparting information then one-way communication is adequate. But if the goal of education is to enable the learner to collect information appropriate to the problem that he faces (not necessarily in the classroom but later in life), then it is much better to have Multiple way communication.
It may be noted here that the multiple way in the classroom gets defined as communication between peers or co-students. But the multiple way which is now getting common in the last decade and which will be getting much more prevalent in the coming century not only with peers in the classroom but with a variety of other sources of learning.
These also include persons that a student has never met, but s/he can interact with them on the Electronic Mail. And such persons may be living in any part of this Earth, which may even be physically inaccessible for our students. All this and more have been made possible by computers, telecommunication, teleconferencing and such other new technology in Education that is emerging.