The Sino-Indian border dispute has a lot to do with Tibet's past.
It is common knowledge that one of the most contentious issues that has bedevilled the bilateral relationship between India and China is the matter of their common boundary. What is not generally known is that the dispute is complicated by the fact that, prior to 1950, Tibet was a ´suzerain´ entity with the power to enter into treaties on its own. In short, the Sino-Indian boundary dispute is embedded in the disputed status of Tibet. What follows is a table that encapsulates various dimensions of the dispute vis-a-vis the Himalayan rimland.
Clues used by early colonial officials to roughly indicate Indo-Tibetan borders included an enthnocultural criterion of whether an area was under "Tibetan influence" or not. This, in practice, meant the presence of Tibetan-speaking villages showing some sort of loyalty to Lhasa and/or the presence of a gompa (monastery) in the said locality connected with one of the major monasteries in Tibet, or simply mountain ranges and passes with Tibetan names. This procedure was followed particularly in the extreme Eastern sector where there were various tribes such as Tawangs, Charduars, Thengla Bhutias, Akas, Daflas, Miris, Abors and Mishmis.
Therefore, if an area was not under "Tibetan influence", it was largely the question of boundary engineering based on such criteria as strategic considerations and topographical suitability: "secure, suitable, strategic borders". In such cases bereft of documentation, it was a question of whose expedition got "there" first, Indian or Chinese, and who put their flag up first. This has implications on the two extremities of the Western and Eastern sectors where Tibetan evidence was lacking.