Re: [Stackevo] Fwd: New Version Notification for draft-hardie-path-signals-02.txt

[Martin Thomson <[e-mail]>]

On Thu, Jan 4, 2018 at 3:33 AM, Eliot Lear <[e-mail]> wrote:
>> I don't think that we need any specific mitigation, but we should
>> recognize that this is a natural consequence of the recommendations in
>> the draft.  That isn't strictly a negative outcome either.  One
>> conceivable - but actually highly unlikely - outcome of designing
>> explicit signals is that intermediaries might insist on a certain set
>> of signals before a packet is allowed to pass ("give me SNI or I kill
>> your flow").  A signal that isn't directly coupled to the actual
>> protocol machinery can be falsified to appease a middlebox, even in
>> cases where the endpoint might otherwise prefer not to provide the
>> information.  I wouldn't include all that exposition though, just note
>> that falsification is possible, without affecting the e2e protocol
>> operation.
>
> I think it's probably worth expanding this point.  Falsification of
> signaling means that middleboxes will not trust it.  To what degree that
> holds true will depend on circumstances, but if it becomes the general
> case, one has to ask what the point of including it was in the first
> place?  That way lies dragons.

That's why I think we are better avoiding saying anything.  The value
of signals will depend greatly on whether endpoints provide accurate
values, and that in turn will depend on the consequences that are
attached to either faithful or falsified values.  I can't predict the
outcome, which remains the big open question in this entire space.
It's certainly true that there is a case for mutual benefit to be
gained by filling explicit signals accurately, but it's not clear if
the gains are as well understood as for other voluntary things, such
as using a sane congestion control algorithm [1].

[1] Side discussion for bonus credit: In TCP, an endpoint that fails
to observe proper sender behaviour with respect to congestion control
can be managed in the network by terminating their TCP connections.
End-to-end protection of the transport prevents that.