Discuss the factors to be taken into account when deciding to which NTP server a client should synchronize its clock.

What will be an ideal response?

The main factors to take into account are the intrinsic reliability of the server as a source of time values, and the quality of the time information as it arrives at the destination. Sanity checks are needed, in case servers have bugs or are operated maliciously and emit spurious time values. Assuming that servers emit the best time values known to them, servers with lower stratum numbers are closest to UTC, and therefore liable to be the most accurate. On the other hand, a large network distance from a source can introduce large variations in network delays. The choice involves a trade-off between these two factors, and servers may synchronize with several other servers (peers) to seek the highest quality data.