All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
As for your saying: “Is there any provision of fencing to safeguard pilgrims from being outside the boundary?”, then know that the Saudi government has already distinguished the boundaries of ‘Arafah by using billboards.
If there happens to be some conflict regarding these billboards, then the individual must try his best to be sure he stays within the boundaries of ‘Arafah for the sake of performing worship in the correct manner, as staying at ‘Arafah is the greatest pillar of the Hajj and whoever misses it has missed the Hajj.
Allaah Knows best.