The Sost dry port is connected by the Karakoram Highway to Gulmit, Aliabad, Gilgit and Chilas on the south and to the Chinese cities of Tashkurgan, Upal and Kashgar in the north. The Northern Areas Transport Corporation offers passenger road service between Islamabad, Gilgit and Sost. Passenger road service between Tashkurgan and Sost also exists. Road service between Kashgar and Gilgit (via Tashkurgan and Sost) started in summer 2006. However, the border crossing between China and Pakistan at Khunjerab Pass (the highest border of the world) is open only between April 1 and November 30. Under the protocol agreement signed by Pakistan and Chinese authorities, the border is usually closed on Nov 30 and reopened on April 1 every year.