Nomads keep dogs to protect yaks from wolves, so you can imagine the temperament and physique of these pets. 'Keep' implies that they are domesticated, but this is a fairly limited use of the word. The Tibetan dogs are bad enough; the Mongolian dogs are positively dangerous. The only defence is attack. Sometimes they are tied up and just cause fright as they leap snarling and frothing through the air only to be snapped back to ground at the end of their chain. Others who are not restrained will run after you, often in packs. People have been badly bitten. It is important to show initiative and cause them to reconsider. Rocks are a standard deterrent, but more persistent attackers will only be driven off by chasing them into their owner's camp, and clobbering them with several large rocks or a handy weapon like a tent pole (from the nomad's tent). There is another breed of large dog - in Tibet, not Mongolia - that wanders the countryside and has no malicious intentions at all, and indeed seems of quite pleasant  disposition, but they run away when they see you.