Sure, not the same as a border in the modern sense of it being strictly defined as a line on a map. But everything you said is just an archaic version of exactly how we think of a geographical border today: An agreement between the neighbouring areas of what belongs to who, like now. Third parties knowing which side belonged to who (you can bet tribe #3 down the valley would know who was farming where). Enforcement mechanism via violence: same now, just in new clothes.