32-bit
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... "original datagram" field MUST be zero padded to the nearest
32-bit boundary.
When the ICMP Extension Structure ...
...
For ICMPv4 messages, the length attribute represents 32-bit words.
When the length attribute is specified, the "original datagram" field
...
... When the length attribute is specified, the "original datagram" field
MUST be zero padded to the nearest 32-bit boundary. Because the
sixth octet of each of the impacted ICMPv4 messages ...
... attribute represents length of the padded "original datagram" field,
measured in 32-bit words.
* The Next-Hop ...
... length attribute represents length of the padded "original datagram"
field, measured in 32-bit words.
...
... length attribute represents length of the padded "original datagram"
field, measured in 32-bit words.
...
...
Each extension object contains one or more 32-bit words, representing
an object header and payload ...