; or (II) bringing an action under subsection (d)(3). (4) Firewalls (A) Buy-side and sell-side brokerages Buy-side brokerages and sell-side brokerages shall establish, maintain, and enforce written policies and procedures reasonably designed to ensure compliance with the obligations under this subsection. (B) Other persons Persons not subject to prohibitions under subsection (b) shall establish, maintain, and enforce written policies and procedures reasonably designed to ensure that the buy-side brokerage, sell-side brokerage, digital advertising exchange, and role as a buyer or seller of digital advertising, as applicable, operate separate and independent from one another and transact business at arm’s length. (5) Fair access duty A digital advertising exchange shall provide every buyer and seller in the exchange fair access, including with respect to operations of the exchange, colocation, any technology systems or data, information related to transactions, service, or products offered, exchange processes, and functionality. (6) Time synchronization A digital advertising exchange, buy-side brokerage, or sell-side brokerage shall— (A) synchronize its business clocks at a minimum to within a 2 milliseconds tolerance of the time maintained by the atomic clock of the National Institute of Standards and Technology