Extension Header
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... The current memo does not define any ICMP extension objects. It
defines only the extension header and a common header that all
extension objects share. [UNNUMBERED ...
... Extension Header. In order to represent a valid
Extension Header, it must contain a valid version number and
...
... - selected octets of the original datagram field represent the
correct values for an extension header version number and
checksum ...
... ICMP message that does
not specify a length attribute, it will parse for a valid extension
header at a fixed location, assuming a 128-octet "original datagram"
field. If the application detects a valid ...
... document.
The Extension Structure contains exactly one Extension Header
followed by one or more objects. Having received an ICMP message
...