Re: [core] [Tsv-art] TSV-ART review of draft-ietf-core-coap-tcp-tls-07

Hi Spencer, 

I’m not Yoshi :-), but I just have started working on an update of
https://lwig-wg.github.io/coap/#rfc.section.6
with some of the new information that relates to CoAP over reliable; I hope that I will be able to push this during this week.

Note that CoAP over TCP/TLS/WS does address application layer acknowledgement beyond the request-response acknowledgement semantics by introducing the custody option of the PING/PONG signaling messages.  This may be useful in compensating the decrease of information available to the CoAP application as a result of moving some of the transport functionality into TCP.

Grüße, Carsten

> On May 8, 2017, at 05:17, Spencer Dawkins at IETF <spencerdawkins.ietf@gmail.com> wrote:
> 
> Hi, Yoshi,
> 
> On Sat, Apr 29, 2017 at 11:24 PM, Yoshifumi Nishida <nishida@sfc.wide.ad.jp> wrote:
> Hello,
> As far as I've read -08 draft, I think this point has not been addressed yet. I hope some folks could elaborate a bit more if they think this is not an important point for the draft.
> 
> I've seen the subsequent e-mails in reply to yours, but it's not obvious to me whether you think this point was addressed after reading those e-mails.
> 
> What do you think?
> 
> Thanks,
> 
> Spencer
>  
> --
> Yoshi
> 
> On Fri, Apr 21, 2017 at 2:57 PM, Brian Raymor <Brian.Raymor@microsoft.com> wrote:
> I think that I understand your perceptions better. Prior to adoption of coap-tcp-tls and before I was active in the WG, I recall discussions related to the confusion over application vs transport reliability in CoAP especially as related to CON and NON. What was intended?
> 
>  
> 
> Tim Carey outlined some concerns in:
> 
> https://tools.ietf.org/html/draft-carey-core-std-msg-vs-trans-adapt-00#section-2
> 
>  
> 
> This topic was presented in detail at IETF 93 - https://www.ietf.org/proceedings/93/slides/slides-93-core-0.pdf - starting on slide 23.
> 
>  
> 
> And in a related thread on the mailing list back in 2015 - https://www.ietf.org/mail-archive/web/core/current/msg06280.html - Carsten responded:
> 
>  
> 
> > In any case, CON and NON are about message layer semantics, not about application semantics
> 
> > -- you gave them a meaning they don't have.
> 
>  
> 
> By IETF 94, the authors were reporting – “Most of the Confusion around              CON/NON was resolved”.
> 
>  
> 
> Where relevant, I’ve added clarifications - such as the Appendix related to differences in Observe for reliable transports.
> 
>  
> 
> Both Carsten and Hannes could probably offer more context if needed.
> 
>  
> 
> From: Yoshifumi Nishida [mailto:nishida@sfc.wide.ad.jp] 
> Sent: Friday, April 21, 2017 2:08 PM
> To: Brian Raymor <Brian.Raymor@microsoft.com>
> Cc: Yoshifumi Nishida <nishida@sfc.wide.ad.jp>; tsv-art@ietf.org; draft-ietf-core-coap-tcp-tls@ietf.org; core@ietf.org; ietf@ietf.org
> Subject: Re: TSV-ART review of draft-ietf-core-coap-tcp-tls-07
> 
>  
> 
> Hi Brian,
> 
>  
> 
> Just in case,
> 
> Reliable transports only provide reliability at transport level. It doesn't provide reliability in application protocol level. 
> 
>  
> 
> RFC7252 has reliability mechanisms in it since it uses UDP. This means it has abilities to check both transport and app level reliability.
> 
> This draft only provides transport level reliability and apps will need to detect app protocol failure by themselves. 
> 
> This means 7252 and this draft are not totally equivalent from the viewpoint of applications. 
> 
>  
> 
> I am not saying this is wrong or bad, but I believe app developer should aware this point.
> 
> --
> 
> Yoshi
> 
>  
> 
> On Fri, Apr 21, 2017 at 11:15 AM, Brian Raymor <Brian.Raymor@microsoft.com> wrote:
> 
> Hi Yoshi,
> 
>  
> 
> > OK. I also think we should state that the protocol should notify the failure events to applications. 
> 
> > Since errors can happen not only in TCP, but also TLS and websocket level, mentioning only TCP close or reset might not
> 
> > be enough.
> 
>  
> 
> After reviewing with the authors, an additional clarification was appended to 3.4 Connection Health - https://github.com/core-wg/coap-tcp-tls/pull/140/files
> 
>  
> 
> The opinion of the authors (and Gengyu WEI’s recent response - https://www.ietf.org/mail-archive/web/core/current/msg08622.html) is that RFC6455 covers the WebSocket case and does not need to be repeated here.
> 
>  
> 
> > When we use 7252, I think applications basically don't need to implement timeouts or retry mechanisms as the protocol
> 
> > provides such things. 
> 
>  
> 
> RFC7252 provides timeouts and retries because it's implementing a TCP-like reliability mechanism over UDP - https://tools.ietf.org/html/rfc7252#section-2.1
> 
>  
> 
> > However, when we use this one, it seems applications will need to have such mechanisms. Isn't it a bit confusing? I am thinking that
> 
> > there need to be some guidance here.
> 
> > BTW, PONG is one example.
> 
>  
> 
> For coap-tcp-tls, there are multiple early implementations. This has never been reported as a source of confusion.
> 
>  
> 
> >> My sense is that we should treat this as an update to RFC7959 based on the original language:
> 
> > I don't have a strong opinion here. Updating 7959 is fine for me if it's clearer to CoAP people.
> 
>  
> 
> I've merged the change - https://github.com/core-wg/coap-tcp-tls/pull/138/files
> 
>  
> 
> Thanks again for helping us to improve the quality of the draft,
> 
>  
> 
> …Brian
> 
>  
> 
> 
> 
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