Re: Proposal for changing how IPv6 Hop-by-Hop Options are processed

[Fernando Gont <[e-mail]>]

On 3/12/20 20:38, Templin (US), Fred L wrote:
> Bob and Gorry,
> 
> I would like it if some document that updates RFC8200 (such as yours) could
> relax the restriction that the Hop-by-Hop option has to immediately follow
> the IPv6 header. This comes up in two different places in RFC8200:
> 
> Section 4:
>     "The Hop-by-Hop Options header, when present, must immediately follow
>     the IPv6 header."
> 
> Section 4.1:
>     "IPv6 nodes must accept and attempt to process extension headers in
>     any order and occurring any number of times in the same packet,
>     except for the Hop-by-Hop Options header, which is restricted to
>     appear immediately after an IPv6 header only."
> 
> I would like to see this restriction softened somewhat (perhaps to a "should")
> since I have a use case in mind where another extension header type might
> appear before the Hop-by-Hop option, if only briefly. Any chance your doc
> could accommodate?

"right after the IPv6 header" since the only natural place where this 
option would belong. At the end of the day, the goal is that the option 
is processed by all nodes -- and if the option is elsewhere, then it 
would not, or would mean that a router would need to skip options e.g. 
destined to the destination in order to process options meant to be 
processed by all nodes.

Unless I'm missing something, I'd strongly argue against relaxing this.

In fact, if we want to have any hopes that things will improve, my 
feeling is that the way to do that would be via *tightening* requirements.

Thanks!

Regards,
-- 
Fernando Gont
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