A. Below is the specification for the header format of IPv6:

VersionĀ  Traffic Class Flow Label
Payload LengthĀ  Next Header Hop Limit
Source Address
Destination Address

Version - 4-bit Internet Protocol version number.

Traffic Class - 8-bit traffic class field

Flow Label - 20-bit flow label

Payload Length -16-bit unsigned integer. Length of the IPv6 payload, i.e., the rest of the packet following this IPv6 header, in octets. (Note that any present are considered part of the payload, i.e., included in the length count.)

Next Header - 8-bit selector. Identifies the type of header immediately following the IPv6 header. Uses the same values as the IPv4 Protocol field \[RFC-1700 et seq.\].

Hop Limit - 8-bit unsigned integer. Decremented by 1 by each node that forwards the packet. The packet is discarded if Hop Limit is decremented to zero.

Source Address - 128-bit address of the originator of the packet.

Destination Address - 128-bit address of the intended recipient of the packet (possibly not the ultimate recipient, if a Routing header is present).

Notice that the IPv6 header has far less fields than the IPv4 header and IPv6 introduces a number of extension headers as defined in RFC 2460.