Re: Spin bit as a negotiated option

[Kazuho Oku <[e-mail]>]

2018年10月5日(金) 21:32 <[e-mail]>:
>
> On 10/05/18 14:22, Brian Trammell (IETF) wrote:
> >
> > I'm less happy about the complexity implied:
> >
> > - in any (non-VEC) implementation of a negotiated spin bit, the negotiation
> > code will dwarf the code for the signal it's negotiating, which seems wrong.
>
> The version negotiation code is a one-shot investment for all extensions. Not a
> single extra line when the set moves from {v1,v1s} to {v1,v1s,v1svv,v1sqr?...}.

+1.

I would also argue that having explicit negotiation using the version
number field helps both the endpoints and the middleboxes, because it
ensures us of having the freedom to evolve.

Having one bit (or several bits) tied forever to the behavior we
define in v1 would be a loss for everybody.

> > - if we decide to support other client behaviors for other measurement goals
> > in the future, it pushes the complexity of deciding what to measure to the
> > endpoints, as opposed to placing that complexity at the midpoint.
> The one thing that pushes the burden onto the endpoints is not negotiation but
> enforcement. I don't think enforcement is a good idea, for this very reason.
> Since these extensions are only for observers and may easily be opted out by
> either endpoint, it makes sense to honor them in a best-effort way, no more.

I would also argue that the endpoints must be given the freedom to
choose the signals they would expose, because there could be privacy
implications based on how the endpoints are deployed.

FWIW, I am not opposed to the idea of middlebox suggesting a signal it
wants to see, possibly by injecting a long header packet into the
flow.

>
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-- 
Kazuho Oku