IPv6 Header Field

C

The answer is C. Flow Label.

IPv6 is the latest version of the Internet Protocol (IP) and was developed as a replacement for IPv4. One of the main differences between IPv4 and IPv6 is the number of bits used in the address. IPv4 addresses are 32-bit numbers, while IPv6 addresses are 128-bit numbers. This allows for a much larger number of possible addresses in IPv6.

IPv6 has several new features that were not present in IPv4. One of these features is the Flow Label header field, which is a 20-bit field that is used to identify packets belonging to a particular flow. A flow is a sequence of packets that share the same source and destination addresses, the same protocol, and the same set of packet header fields.

The Flow Label field was added to IPv6 to help with Quality of Service (QoS) and traffic engineering. By identifying packets belonging to a particular flow, network devices can prioritize and route the packets more efficiently. For example, a router could give priority to packets belonging to a real-time video stream, while delaying packets belonging to a file transfer.

The other header fields mentioned in the question, Version, Hop Limit, and Traffic Class, are all present in both IPv4 and IPv6. The Version field is used to indicate the version of the IP protocol being used (either 4 or 6). The Hop Limit field is used to limit the number of hops a packet can take before being discarded, and the Traffic Class field is used to indicate the priority of the packet.

In summary, the Flow Label header field is a new feature in IPv6 that allows packets belonging to a particular flow to be identified and handled more efficiently.