The header of an IPv6 packet has been designed to be simpler than the IPv4 header, with the goal of facilitating more efficient processing in routers.

The IPv6 header consists of 8 fixed fields, compared to the 13 possible fields (including options) that an IPv4 header might have.

The IPv6 basic header fields are as follows:

1. Version: 4 bits that indicate the version of the IP protocol, which for IPv6 is the number 6.
2. Traffic Class: 8 bits used to differentiate traffic on the network, similar to the Type of Service field in IPv4.
3. Flow Label: 20 bits used to label packet sequences that require special handling by routers.
4. Payload Length: 16 bits that indicate the length of the packet payload, that is, everything that follows the IPv6 header, in octets.
5. Next Header: 8 bits that identify the type of header immediately following the IPv6 header. It works similar to the Protocol field in IPv4 and is used to indicate whether the next header is TCP, UDP, ICMPv6, etc.
6. Hop limit: 8 bits that specify the maximum number of hops (routers traversed) that the packet is allowed to make before being discarded. It is similar to the TTL field in IPv4.
7. source address: 128 bits indicating the IPv6 address of the packet sender.
8. Destination address: 128 bits indicating the IPv6 address of the recipient of the packet.

These fields are organized in a 40-byte header. The simplification in design seeks to improve processing speed in network devices, eliminating the need to summarize or fragment packets in intermediate routers, which is handled at the ends in IPv6.