The eastern border with Vietnam extends for 2,130 kilometers, mostly along the crest of the Annamite Chain, and serves as a physical barrier between the Chinese-influenced culture of Vietnam and the Indianized states of Laos and Thailand. These mountains are sparsely populated by tribal minorities who traditionally have not acknowledged the border with Vietnam any more than lowland Lao have been constrained by the 1,754-kilometer Mekong River border with Thailand. Thus, ethnic minority populations are found on both the Laotian and Vietnamese sides of the frontier. Because of their relative isolation, contact between these groups and lowland Lao has been mostly confined to trading.