8.1 Next Headers of IP Version 6 Datagram

Next headers can follow the base header.

The Next header field in the base header shows, which data type (header) follows the base header. Headers form chains. The chain contains only those headers that are necessary as opposed to IP version 4 that often carries extraneous information in its header.

Figure 8.2: An example of IP version 6 datagram structure with arrows showing the order of header processing

The Next header field is followed by the header length field. This field specifies the shift that is necessary in order to reach the next header. The base header does not have a header length field since it is always 40 bytes long. The length is not used with fragment headers either since this header is always 8 bytes long.