Re: HBH Option Header Configuration (draft-hinden-6man-hbh-processing)

On Tue, Jun 8, 2021 at 1:49 PM Brian E Carpenter
<brian.e.carpenter@gmail.com> wrote:
>
> On 09-Jun-21 08:18, Nick Hilliard wrote:
> > Bob Hinden wrote on 08/06/2021 21:06:
> >> We have discussed this and conclude that yes, we are proposing to
> >> require all nodes to examine and process the first HBH Option in the
> >> Fast Path.   Not just drop packets with HBH Option Headers.  This
> >> change needs to be made clearer in the draft.
> > [...]
> >> Comments?
> >
> > yep - it's 26 years too late to close this particular stable door.
>
> I wouldn't say it exactly like that, but I think the requirement is
> totally unrealistic. To be precise:
>
I agree.

> "However, it
> is to be expected that high-performance routers will either ignore it
> or assign packets containing it to a slow processing path.  Designers
> planning to use a hop-by-hop option need to be aware of this likely
> behaviour."

Yes, that is the why when sending options from a host, we'd never
assume that *all* nodes in the path are going to process any of them.
The assumption we're making is that routers in the path that need to
process the option will process them, and those that don't need to
process them will forward (in the fast path) instead of just dropping
them. For example, in FAST the hop by hop option is really directed to
the first hop router of the local network and/or the ingress router of
a remote network-- any other routers in the path don't need to process
it and can ignore it (either by skipping the option with 00 in high
order bits, or by ignoring the HBH EH altogether).

Tom

>
> [https://www.rfc-editor.org/rfc/rfc7045.html#section-2.2]
>
> (Standards wonk comment: Since RFC8200 does not obsolete or update
> RFC7045, this draft would need to formally update RFC7045 for this
> reason. Which I would object to...)
>
> Regards
>    Brian
>
> >
> > Nick
> >
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