A.LDP hello packets are sent to UDP port 646
B.LDP hello packets are sent to TCP port 711
C.LDP sessions are TCP sessions to port 646
D.LDP sessions are TCP sessions to port 711
E.LDP establishes a peer relationship with another router that must be directly attached
F.LDP can establishes a peer relationship with another router that is not directly attached

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.