Re: [core] Review of draft-koster-core-coap-pubsub-05

[Jim Schaad <[e-mail]>]

> -----Original Message-----
> From: Hannes Tschofenig [mailto:[e-mail]]
> Sent: Thursday, August 11, 2016 1:16 AM
> To: Jim Schaad <[e-mail]>; draft-koster-core-coap-
> [e-mail]; [e-mail]
> Subject: Re: [core] Review of draft-koster-core-coap-pubsub-05
> 
> Hi Jim,
> 
> let me share my views on this document.
> 
> On 08/04/2016 05:35 AM, Jim Schaad wrote:
> > I have a hard time saying that this is ready to be published, but that
> > is in part because I think that the security aspects that are not
> > being addressed in the document are important.
> >
> >
> > Section 3.2 - The phrase "and potentially buffer messages" is causing
> > me problems.  By definition it must buffer the last data value that it
> > includes.  It would be good at this point to explain exactly why it is
> > buffering messages here.  I assume that you are talking about the flow
> > control issues that are discussed later but I don't know this.
> 
> The reason why the pub/sub broker buffers messages is because the IoT
device
> is sleeping most of the time. For that reason, it cannot always forward
requests
> from applications immediately.
> 
> This is functionality called 'queue mode' in LWM2M and other terms have
been
> used in other IETF documents.

I agree that having a 'queue mode' would be a nice feature, but I do not
believe that this is documented anyplace in this document.  Doing so would
require some additional text.  The current text says that messages are
always forwarded when they are received to a client.  If the client happens
to be asleep then it needs to go back and ask for the current value when it
wakes up.  

> 
> In my review I have been wondering why we aren't re-using the concepts
from
> LWM2M here.
> 
> Regarding the "topics": I have read this a bit differently. For me, a node
has
> resources and it publishes those. Then, there are applications (Web
applications,
> smart phone apps) who sent requests for those resources. These resources
have
> to be identified somehow and in LWM2M there is a specific way of
addressing
> the standardized resources (and objects), as described in
> https://www.iab.org/wp-content/IAB-uploads/2016/03/ipso-paper.pdf. Maybe
> you want to be more generic here but I think it is important that there is
a
> standardized structure here and that we are not only talking in the style
of MQTT
> topics.

I do not follow how this came from my review.  Is this an independent item
or is it following from something that I asked in my review?

Jim

> 
> 
> Ciao
> Hannes