Re: [Errata Held for Document Update] RFC8200 (5933)

[Fernando Gont <[e-mail]>]

On 3/3/20 18:43, Brian E Carpenter wrote:
[....]
>> It seems to me that the bigger question is whether there would be
>> consensus to update RFC8200 to allow whatever SPRING wants to do.
> 
> SPRING is not asking for an update to 8200; their claim is that it
> already allows the PSP action. You might disagree, of course.

FWIW, segment-routing-header also argued that en-route insertion was 
allowed.



[....]
> 
> IMHO the questions of principle (does it violate the words in RFC8200,
> and are those words correct?) are much less important than Robert Raszuk's
> question: what harm does this do? And we have the answers to that, I think:
> 
> - doesn't harm PMTUD, because making a packet shorter on the last hop can't
> possibly harm PMTUD.
> 
> - doesn't describe AH rules (which fields are mutable), but AH is not used in
> SRH domains.
> 
> - may affect OAM mechanisms.

FWIW, one would expect that whether this functionality violates RFC8200 
should be connected with whether this causes harm.

If it doesn't then RFC8200 is being overly prescriptive, and should be 
relaxed (updated)

If it does cause harm, and violated RFC8200, then that might be an 
indication that a different solution should be evaluated.

The requirements in RFC8200 sets expectations on what happens to IPv6 
packets. Encouraging a disconnect between what the spec says, and what 
actually happens (particularly when it's us doing that) is, IMO, harmful.

-- 
Fernando Gont
SI6 Networks
e-mail: [e-mail]
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