What is "abarshahr"

Abarshahr was a Sasanian province in Late Antiquity, that lay within the kust of Khorasan. The province bordered Media in the west, Hyrcania in the north west, Margiana in the north east, and Harev in the south east. The governor of Abarshahr is attested to have held the unique title of kanarang, distinguished from the title of marzban given to governors of frontier provinces.