What is a secure way of providing clock synchronization between network routers?
A.
sync each router acting as an NTPv2 client to the UTC via the Internet
B.
implement an NTPv3 server synchronized to the UTC via an external clock source like a radio or atomic clock, then configure the other routers as NTPv3 clients
C.
use CDPv2 and NTPv3 to pass and sync the clocking information between the adjacent routers in the network
D.
implement in-band management to sync the clock between the routers using a peer-to-peer architecture using NTPv4 or higher