Subject: [homenet] Benoit Claise's Discuss on draft-ietf-homenet-dncp-11: (with DISCUSS and COMMENT)

From: "Benoit Claise" <[email-masked]>
Date: Tue, 20 Oct 2015 13:41:59 -0700

Benoit Claise has entered the following ballot position for
draft-ietf-homenet-dncp-11: Discuss

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DISCUSS:
----------------------------------------------------------------------

Other ADs focused on the protocol specific points. So let me focus on
something else.
The applicability section doesn't answer my questions: when to (re-)use
this protocol?
Note that the write-up mentioned ANIMA.

I see the protocol description:

   DNCP is designed to provide a way for each participating node to
   publish a set of TLV (Type-Length-Value) tuples, and to provide a
   shared and common view about the data published by every currently or
   recently bidirectionally reachable DNCP node in a network.

However, this applicability section doesn't tell me when to re-use DNCP
(or define a profile for it).
I see an effort to address my discuss in the appendix B of draft version
11. Thanks 

What would solve my DISCUSS is an applicability section that would
contain 
a high level set of criteria that would briefly explain whether DNCP is
applicable for 
the specifications I have in mind. The first 2 paragraphs of section 1.1
is a good start, 
then it goes considerations about Trickle, the interval A_NC_I, etc ...
and you lose the 
readers.  

Something like:

   DNCP is designed to provide a way for each participating node to
   publish a set of TLV (Type-Length-Value) tuples, and to provide a
   shared and common view about the data published by every currently or
   recently bidirectionally reachable DNCP node in a network.

   [As an example of what I'm expected, see below. 
    Btw, I have no idea if this text is correct or complete, but that's
besides the point] 

   DNCP works with profiles in which you have the flexibility to
specify:
   - the appropriate transport: the available options are TCP and UDP
(see 
   section appendix B for the tradeoffs)
   - the transport security: TLS or DTLS, see appendix B). 
   - If service discovery is required, an optional multicast service can
be defined.   
   - TO BE COMPLETED

   DNCP is applicable to LAN, WAN, or even the Internet. 
   DNCP can exchange enterprise specific TLV or an IANA registry could be
specified
   DNCP specific extensions are possible.
   TO BE COMPLETED
 
   DNCP limitations:	
	- Data published limited to 64kB
	- Doesn't work for SCTP, DCCP 
        - All devices in the network must be DNCP node?
        - TO BE COMPLETED 

To summarize, I need the 2 min elevator pitch of when (not) to use DNCP.

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COMMENT:
----------------------------------------------------------------------

- I would agree with Alvaro, when he wrote: "In general, I found the text
not straight forward or easy to understand." Potentially due to the
structure.

- I hope that a document about manageability considerations (see
https://tools.ietf.org/html/rfc5706#appendix-A) will follow.

---

From: Steven Barth <[email-masked]>
Date: Wed, 21 Oct 2015 15:30:57 +0200

Hello Benoit,

thanks for your feedback.

I've staged the following additions for -12 in our Git:
https://github.com/fingon/ietf-drafts/commit/859a37237

Would that address your DISCUSS? If not, please let us know what you
would like us to add or change in addition.

Thanks,

Steven

On 20.10.2015 22:41, Benoit Claise wrote:
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From: Benoit Claise <[email-masked]>
Date: Wed, 21 Oct 2015 16:12:28 +0200

Steven,

Thanks, that goes in the right direction.
Trying to answer the question "when not to use DNCP?", do I understand 
correctly that there is only one limitation: the **64kB size
Except that, DNCP is generically applicable. Really?

Regards, B.
> .

---

From: Steven Barth <[email-masked]>
Date: Wed, 21 Oct 2015 16:39:08 +0200

Hello Benoit,

On 21.10.2015 16:12, Benoit Claise wrote:
> Trying to answer the question "when not to use DNCP?", do I > understand correctly that there is only one limitation: the 64kB >
size Except that, DNCP is generically applicable. Really?

No, that is not true. The applicability section also mentions e.g.:

1. "each node needs to be able to store the entirety of the data
published by all nodes"

2. "As the [...] frequency of data changes per node increases [...]
the benefit of using DNCP diminishes."

3. "If the TLV set published by a node is very large, and has
frequent small changes, DNCP as currently specified in this
specification may be unsuitable as it lacks a delta synchronization
scheme to keep implementation simple."

I'm not sure what other points could be added, however it intentionally
is designed as a generic TLV-sharing protocol so its potential applicability
is broad.

Could you please provide some guidance on other factors we should
evaluate in the Applicability section? We are currently feeling a bit lost
on how we should address your concerns.

Thanks,

Steven

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From: Juliusz Chroboczek <[email-masked]>
Date: Thu, 29 Oct 2015 14:47:23 +0100

> No, that is not true. The applicability section also mentions e.g.:

[...]

> I'm not sure what other points could be added,

Since every change in the set of neighbours of a node causes reflooding,
DNCP is not suitable in environments where high levels of node mobility
are expected?

-- Juliusz