IPv6 Datagram Options

In IPv4, all extra information required for various purposes is placed into the datagram in the form of options that appear in the IPv4 header. In IPv6, the new concept of extension headers is introduced, as you just saw. These headers take the place of many of the predefined IPv4 options. However, the concept of options is still maintained in IPv6 for a slightly different purpose.

Options allow the IPv6 datagram to be supplemented with arbitrary sets of information that aren't defined in the regular extension headers. They provide maximum flexibility, thereby allowing the basic IPv6 protocol to be extended in ways the designers never anticipated, with the goal of reducing the chance of the protocol becoming obsolete in the ...

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