title: IPv4/IPv6 protocol/next header value in empty payload case
body: <p>Which is the value of the protocol field (IPv4 header) or next-header field (IPv6 header) in the case that there is no payload (empty)?</p>
  
  <p>I looked in the <a href="https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers" rel="nofollow noreferrer">list of protocol numbers</a> but 0x00 specify a protocol and there aren't special values.</p>