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Re: [6tisch] SeqNum definition in RFC8480 (6P)

Yasuyuki Tanaka <yasuyuki.tanaka@inria.fr> Wed, 24 April 2019 10:24 UTC

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From: Yasuyuki Tanaka <yasuyuki.tanaka@inria.fr>
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Date: Wed, 24 Apr 2019 12:24:26 +0200
Cc: Yasuyuki Tanaka <yasuyuki.tanaka@inria.fr>, 6tisch@ietf.org
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To: Xavi Vilajosana Guillen <xvilajosana@uoc.edu>
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Subject: Re: [6tisch] SeqNum definition in RFC8480 (6P)
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Hi Xavi,

> What is the issue you see with this?

At least, there is an inconsistency in RFC8480. Here is another example:

https://tools.ietf.org/html/rfc8480#section-3.2.2

rfc8480>   6P Request, 6P Response, and 6P Confirmation messages for a given
rfc8480>   transaction MUST share the same Version, SFID, and SeqNum values.

Such an inconsistency could bring confusion and/or an interoperability issue.

According to you, a response having SeqNum=0 AND RC_ERR_SEQNUM has a special
meaning which is "I've lost all the states completely (due to power-cycle)",
although this is another case we will receive such a response as shown in
Figure 32... Honestly, I'm not sure how valuable it is to know the peer has
performed power-cycle, by the way.

So, if setting 0 to SeqNum of a response is a right thing, I would add some
text to the SeqNum definition in Section 3.2.2, to tell there is an exception. 

Best,
Yatch

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