Why is IPv6 needed in the world today?

A. It does not require NAT to operate.
B. The IPv4 address space is exhausted.
C. IPv4 is considered legacy, and IPv6 is the replacement.
D. IPv6 does not require subnetting.

B. IPv4 allows for 2 32 = 4.3 billion addresses. However, only 3.7 billion are usable, because of reservations and classful addressing. The current IPv4 address space is exhausted.