Which of the following choices BEST describes the major difference between IPv4 vs. IPv6? IPv4 headers do not include a fragmentation offset field whereas IPv6 headers do. IPv6 does not allow flow labeling whereas IPv4 does allow it. IPv6 does not allow for fragmentation/reassembly nor does it compute header checksums. IPv4 source/destination IP addresses are 128 bits long whereas IPv6 source/destination IP addresses are 32 bits long.