Re: Spin bit decision

[Kazuho Oku <[e-mail]>]

2018年10月3日(水) 2:18 Ian Swett <ianswett=[e-mail]>:
>
> One piece of information related to the above discussion is whether detecting who is and is not spinning is easy and reliable.

+1.

>From practical standpoint, it is very difficult to design a mechanism
that detects if the peer is not sending false information using the
spin bit. We need to make sure that a middlebox cannot disrupt a
connection by reordering packets, leading an endpoint to believe that
the peer is faking the spin bits. The design needs take care of
multithreaded (or clustered) endpoints sending packets.

I am not against adopting the spin bit proposal, but I strongly prefer
having the possibility to *not* use the spin bits for the endpoints
that want to hide the latency. For example for the endpoints could for
example be behind a NAT or a UDP proxy.

OTOH, I think it is fine to expose a signal that indicates if the spin
bit is turned on. We have an unused bit in the short header :-)

> One of my concerns is unintentional mis-use of the signal, and if it can't be detected reliably in a mixed environment, that means SHOULD is unwise and argues for either not including it or making it a MUST.
>
> On Tue, Oct 2, 2018 at 12:51 PM Mike Bishop <[e-mail]> wrote:
>>
>> I don’t think it’s a grim view, I think it’s a pragmatic view.  Our role is to specify the things which are fundamental to the protocol and have to happen for peers to interoperate.  Mis-using normative language for other things is an abuse of the process -- that's kind of the point of RFC 6919.
>>
>>
>>
>> RFC 2119 says:
>>
>> In particular, [normative language] MUST only be used where it is actually required for interoperation or to limit behavior which has potential for causing harm (e.g., limiting retransmisssions)  For example, they must not be used to try to impose a particular method on implementors where the method is not required for interoperability.
>>
>>
>>
>> Given that the spin bit is not “actually required for interoperation,” but is the very definition of “try to impose a particular method on implementors,” I’d say that RFC 2119 imperatives are unwarranted.
>>
>>
>>
>> -----Original Message-----
>> From: QUIC <[e-mail]> On Behalf Of [e-mail]
>> Sent: Tuesday, October 2, 2018 8:05 AM
>> To: Lars Eggert <[e-mail]>
>> Cc: IETF QUIC WG <[e-mail]>
>> Subject: Re: Spin bit decision
>>
>>
>>
>> On 10/02/18 16:00, Lars Eggert wrote:
>>
>> >
>>
>> > The point I can't seem to be getting across is that irrespective of
>>
>> > what the WG decides to require, there is no penalty for individual
>>
>> > stacks at deployment time (or after) to do whatever they wish, since
>>
>> > the spin bit by design has no impact on protocol operation and interop.
>>
>>
>>
>> It is getting across, but it is a very grim view of the standardization process itself. Are there many examples of MUST in RFCs that turned out to be ignored by implementations just because they were not part of the core semantics and hence not enforced by other peers ?
>>
>>
>>
>>
>>
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-- 
Kazuho Oku