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On 05/05/2020 21:44, Gert Doering wrote:
>> We should print "PW Ethernet Control Word" and the "Sequence Number", 2 last 
>> 2 octets of the 4.
>> Like:
>> PW Ethernet Control Word, Sequence Number xxx
> I think we should only print this if "-v" is given.  Most of the time, 
> both control word and sequence number are of little interest.
> I really like tcpdump's very compact "only the most relevant info" output
> format (by default).

OK for "-v" only print.

Other information from Francesco Fondelli:

it is a bit more complicated than that, look for

     * No, there isn't, so use the 1st nibble logic (see BCP 4928,
     * RFC 4385 and 5586).


and also the PW ETH heuristic in looks_like_plain_eth


Wireshark MPLS heuristic is not perfect and has been criticized but is still 
there :-) hopefully
correctly parsing your data as well.

For tcpdump maybe a -T based approach is better?

-T mpls (+ 1st nibble logic for IPv4/IPv6)
-T ethpw
-T ethpwnocw

Probably some more work to do...

And probably linked to https://tools.ietf.org/html/rfc8469.


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