ICMPv6 messages
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... 4443draft
defines the "original datagram" field for ICMPv6 messages. In RFC
4443draft, the "original datagram ...
...
It also introduces an 8-bit length attribute to the following ICMPv6
messages.
- Destination ...
... ICMPv4.
For ICMPv6 messages, the length attribute represents 64-bit words.
When the length attribute is specified, the "original datagram ...
... MUST be zero padded to the nearest 64-bit boundary. Because the
fifth octet of each of the impacted ICMPv6 messages was reserved for
future use, this octet was selected as the location of the length
attribute in ICMPv6 ...