Re: [Dots] Mirja's DISCUSS: Pending Point (AD Help Needed)

"Jon Shallow" <supjps-ietf@jpshallow.com> Fri, 19 July 2019 08:53 UTC

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From: "Jon Shallow" <supjps-ietf@jpshallow.com>
To: <mohamed.boucadair@orange.com>, "'Benjamin Kaduk'" <kaduk@mit.edu>, <dots-chairs@ietf.org>, <dots@ietf.org>
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Date: Fri, 19 Jul 2019 09:53:38 +0100
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Subject: Re: [Dots] Mirja's DISCUSS: Pending Point (AD Help Needed)
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Hi there,

I concur with what Med is saying.

"If it is not broken, do not fix it".

IETF 103 Interop ( https://datatracker.ietf.org/meeting/103/materials/slides-103-dots-interop-report-from-ietf-103-hackathon-00.pdf ) did exhaustively test out the heartbeat mechanism (and the interactions with other parts of the DOTS protocol) under attack scenarios and found that the then version of the DOTS signal draft worked as expected.

Yes, we can move the heartbeat mechanism into the DOTS layer, but that will require changes to the DOTS signal draft and will again need to be thoroughly tested for functionality (in particular interaction with other parts of the protocol definitions) under adverse network conditions.

Regards

Jon

> -----Original Message-----
> From: Dots [mailto: dots-bounces@ietf.org] On Behalf Of ietf-supjps-mohamed.boucadair@orange.com
> Sent: 19 July 2019 07:57
> To: Benjamin Kaduk (kaduk@mit.edu); dots-chairs@ietf.org; dots@ietf.org
> Subject: [Dots] Mirja's DISCUSS: Pending Point (AD Help Needed)
> 
> Hi Ben, chairs, all,
> 
> (restricting the discussion to the AD/chairs/WG)
> 
> * Status:
> 
> All DISCUSS points from Mirja's review were fixed, except the one discussed in
> this message.
> 
> * Pending Point:
> 
> Rather than going into much details, I consider the following as the summary
> of the remaining DISCUSS point from Mirja:
> 
> > I believe there are flaws in the design. First it’s a layer violation, but
> > if more an idealistic concern but usually designing in layers is a good
> > approach. But more importantly, you end up with un-frequent messages
> which
> > may still terminate the connection at some point, while what you want is
> > to simply send messages frequently in an unreliable fashion but a low rate
> > until the attack is over.
> 
> * Discussion:
> 
> (1) First of all, let's remind that RFC7252 does not define how CoAP ping must
> be used. It does only say:
> 
> ==
>       Provoking a Reset
>       message (e.g., by sending an Empty Confirmable message) is also
>       useful as an inexpensive check of the liveness of an endpoint
>       ("CoAP ping").
> ==
> 
> How the liveness is assessed is left to applications. So, there is ** no layer
> violation **.
> 
> (2) What we need isn't (text from Mirja):
> 
> > to simply send messages frequently in an unreliable fashion but a low rate
> > until the attack is over "
> 
> It is actually the other way around. The spec says:
> 
>   "... This is particularly useful for DOTS
>    servers that might want to reduce heartbeat frequency or cease
>    heartbeat exchanges when an active DOTS client has not requested
>    mitigation."
> 
> What we want can be formalized as:
>  - Taking into account DDoS traffic conditions, a check to assess the liveness of
> the peer DOTS agent + maintain NAT/FW state on on-path devices.
> 
> An much more elaborated version is documented in SIG-004 of RFC 8612.
> 
> * My analysis:
> 
> - The intended functionality is naturally provided by existing CoAP messages.
> - Informed WG decision: The WG spent a lot of cycles when specifying the
> current behavior to be meet the requirements set in RFC8612.
> - Why not an alternative design: We can always define messages with
> duplicated functionality, but that is not a good design approach especially
> when there is no evident benefit.
> - The specification is not broken: it was implemented and tested.
> 
> And a logistic comment: this issue fits IMHO under the non-discuss criteria in
> https://www.ietf.org/blog/discuss-criteria-iesg-review/#stand-undisc.
> 
> * What's Next?
> 
> As an editor, I don't think a change is needed but I'd like to hear from Ben,
> chairs, and the WG.
> 
> Please share your thoughts and whether you agree/disagree with the above
> analysis.
> 
> Cheers,
> Med
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