Which two statemets are true？（）

• A、DPT/RPR uses a bi-directional ring consisting of two symmetric counter rotating fibre rings.
• B、DPT/RPR is defined in the IEEE 802.17 standard and it uses Token Bucket system to avoid collisions on the fiber.
• C、In DPT/RPR rings， data packets can be sent in one direction （downstream） and the corresponding control packets in the opposite direction （upstream），thus using both fibres concurrently to maximise bandwidth.
• D、DPT/RPR can be deployed in the Core of the SP networks where point-to-point POS links are used tomake best use of the Bandwidth.