"Đại Việt" or "Great Viet" is the former name Vietnam today.
"Kinh" or "Viet" is ethnic majority in Vietnam.
I think you don't know the Battle of Bach Dang River in 938, because if you know it you did not say that.
Battle of Bach Dang River (938) - Wikipedia, the free encyclopedia
http://www.defence.pk/forums/world-affairs/164062-india-enhancing-ties-vietnam-energy-infra.html#post2678521
Seriously, if Vietnam was still part of China, Vietnam people would live a much better life now. Consider the good geographic condition of Vietnam. Hanoi might be another Shanghai. And the towns along the coast must be super rich.
And there are no racial problems, you cannot tell a Vietnam people from Chinese. And China has a very good minorities benefitted policy.
I see the only losers are a few Vietnam politicians who are obssessed with power.