ded and are provided in the form of extensions headers. The following list summarizes the main extension headers and their purposes. For the latest list of extensions headers please consult IANA's registry at http://www.iana.org/ assignments/protocol-numbers/protocol-numbers.xml Destination Options and Hop-by-hop Options Header The Hop-by-hop and Destination Options headers are the only options containing additional options that are being processed at least by the destination [21]. The Hop-by-hop Options header is the only extension header that is processed by all nodes on a packet's path. The option number space is shared by both Hop-by-hop and Destination options, and with exceptions the same options can appear on both. All of the options share the same Type-Length-Value format, and furthermore are embed into the two most significant bits of the 8-bit type-value field information about what node handling the packet must do if it does not recognize the option type. The four rules are: 'skip', 'discard', 'discard and send ICMPv6 Parameter Problem', and 'discard and send ICMPv6 Parameter Problem if the destination was not a multicast address'. This framework allows the introduction of new options in a backwards compatible manner. A third most significant bit of the type value indicates whether or not the option is allowed to change in transit, and hence whether the option content is to be included in the AH protection or not. Currently defined options are the following. The list notes whether an option is only allowed to be present in the Hop-by-hop or Destination Options header: Pad1 Option: A special case option, which has a total length of one and content of zero. This can be used when padding of just a single byte is required [21]. PadN Option: An option that allows padding of two or more bytes [21]. Jumbo Payload Option: This option, which is only allowed to be present in the Hop-by- hop Options Header, allows increasing the IPv6 packet's maximum length from - 1 (65535) bytes all the way up-to 232 - 1 (4,294,