IPV6 vs IPV4

• IPv6 header is much simpler than IPv4 header.

• The size of IPv6 header is much bigger than that of IPv4 header, because of IPv6 address size. IPv4 addresses are 32bit binary numbers and IPv6 addresses are 128 bit binary numbers.

• In IPv4 header, the source and destination IPv4 addresses are 32 bit binary numbers. In IPv6 header, source and destination IPv6 addressesare 128 bit binary numbers.

• IPv4 header includes space for IPv4 options. In IPv6 header, we have a similar feature known as extension header. IPv4 datagram headersare normally 20-byte in length. But we can include IPv4 option values also along with an IPv4 header. In IPv6 header we do not have options, but have extension headers.

• The fields in the IPv4 header such as IHL (Internet Header Length), identification, flags are not present in IPv6 header.

• Time-to-Live (TTL), a field in IPv4 header, typically used for preventing routing loops, is renamed to it's exact meaning, "Hop Limit".

FLOW LABEL (20 bits): The sender has the ability to specify a value in this field which identifies a group of packets as belonging to the same flow. The flow value is viewed in tandem with the source address when providing quality of service management