Re: [arch-d] I-D Action: draft-iab-protocol-maintenance-08.txt

[Eric Rescorla <[e-mail]>]

I'm finding myself a little unsure on where exactly to locate
the disagreements here. Perhaps a hypothetical would help.

Suppose we have a protocol that consists of a set of tag-length-values
fields. A message consists of a length field followed by a list of
TLVs.  The protocol defines the following requirements for how a
message is constructed:

1. A given tag MUST only appear once
2. TLVs MUST appear in ascending tag order (this can help
   detect violations of the previous condition)

Question 1: How should implementations behave upon receiving the
following messages, absent any other spec guidance?

- Tags: 1, 2, 2  [Violates rule 1]
- Tags: 1, 3, 2  [Violates rule 2]


Question 2: Should we provide specification guidance for how to handle
these rule violations, and if so, how?

Question 3: Do you think the answers depend on other properties of the
protocol? If so, what are they?

-Ekr



On Tue, Jul 12, 2022 at 4:44 PM Brian E Carpenter <
[e-mail]> wrote:

> I still find it hard to accept that there is community consensus for
> this document as it stands. Most of what its says is correct but it
> still seems to unreasonably claim universal scope.
>
> Some suggestions:
>
> Title: The Robustness Principle May Have Harmful Consequences
>
> Last sentence of Abstract:
> For some types of protocol that are actively maintained, the
> robustness principle can, and should, be avoided.
>
> And a few changes in the main text such as:
> OLD:
> Time and experience shows that negative consequences to interoperability
> accumulate over time if implementations apply the robustness principle.
>
> NEW:
> Time and experience shows that negative consequences to interoperability
> sometimes accumulate over time if implementations apply the robustness
> principle.
>
> Even with changes like this, I'm not sure everyone will agree.
>
> Regards
>     Brian Carpenter
>
> On 12-Jul-22 10:30, [e-mail] wrote:
> >
> > A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> > This draft is a work item of the Internet Architecture Board IETF of the
> IETF.
> >
> >          Title           : The Harmful Consequences of the Robustness
> Principle
> >          Authors         : Martin Thomson
> >                            David Schinazi
> >    Filename        : draft-iab-protocol-maintenance-08.txt
> >    Pages           : 15
> >    Date            : 2022-07-11
> >
> > Abstract:
> >     The robustness principle, often phrased as "be conservative in what
> >     you send, and liberal in what you accept", has long guided the design
> >     and implementation of Internet protocols.  The posture this statement
> >     advocates promotes interoperability in the short term, but can
> >     negatively affect the protocol ecosystem over time.  For a protocol
> >     that is actively maintained, the robustness principle can, and
> >     should, be avoided.
> >
> >
> > The IETF datatracker status page for this draft is:
> > https://datatracker.ietf.org/doc/draft-iab-protocol-maintenance/
> >
> > There is also an HTML version available at:
> > https://www.ietf.org/archive/id/draft-iab-protocol-maintenance-08.html
> >
> > A diff from the previous version is available at:
> > https://www.ietf.org/rfcdiff?url2=draft-iab-protocol-maintenance-08
> >
> >
> > Internet-Drafts are also available by rsync at rsync.ietf.org:
> :internet-drafts
> >
> >
> > _______________________________________________
> > I-D-Announce mailing list
> > [e-mail]
> > https://www.ietf.org/mailman/listinfo/i-d-announce
> > Internet-Draft directories: http://www.ietf.org/shadow.html
> > or ftp://ftp.ietf.org/ietf/1shadow-sites.txt
>
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