Re: [core] CBOR Encoding of Data Modeled with YANG

[Michel Veillette <[e-mail]>]

Hi Juergen

The algorithm proposed to generate IDs  is described in
https://tools.ietf.org/html/draft-veillette-core-cool-00#section-6.

- IDs are assigned based on there location in the schema tree.

- Each type of object (Data node IDs, Notification IDs, Notification parameter IDs,
   Protocol Operation IDs, Input parameter IDs, Output parameter IDs)
   have a different namespace.

   This approach help keeping the same IDs  when updating a module.
   New objects can be added at the end of each list without affecting the existing IDs.

- When an object is added within a list or within the schema tree, its ID can be
   manually assigned using a YANG extension to avoid braking backward compatibility. 
   Alternatively, data nodes can be added using the augment statement.
   In this case, IDs are associated to a different module ID.

  https://tools.ietf.org/html/draft-veillette-core-cool-00#section-7.3 show an
  example of use of the augment statement, see data node ID 68620 bellow.
 
   CoAP response:
     2.05 Content Content-Format(application/cbor)
     {
       66560 : {
         1 : {
           2 : [
             {
               3 : "eth0",
               4 : "Ethernet adapter Local Area Connection",
               5 : "ethernetCsmacd",
               6 : true,
               68620 : {
                 13 : true,
                 14 : true,
                 15 : 1280,
                 16 : [
                   {
                     17 : "fe80::200:f8ff:fe21:67cf",
                     18 : 10
                   }
                 ]
               }
             }
           ]
         }
       }
     }
   

-----Original Message-----
From: Juergen Schoenwaelder [mailto:[e-mail]] 
Sent: December-07-15 3:38 PM
To: Michel Veillette <[e-mail]>
Cc: Core <[e-mail]>
Subject: Re: [core] CBOR Encoding of Data Modeled with YANG

On Mon, Dec 07, 2015 at 08:31:03PM +0000, Michel Veillette wrote:
> Hi Juergen
> 
> My "smart" quote are now disabled.
> Thanks to motivate me to turn off this nonsense.
> 
> About the format/assignment of the numeric data node IDs, the consensus is to keep them out of the YANG to CBOR mapping draft in order to make progress. 
>

But this does not make sense. The naming must be settled, even if it is painful.

> Peoples agree that names encoded as string represents too much overhead to address the needs of constrained devices and constrained networks as defined by RFC 7228. However, there are lots of discussions about how those names can be associated with small IDs encoded as integers and how small those integers need to be.
> 
> The CoOL draft proposes structured IDs based on the following concept:
> 
>    Only IDs  associated with module names are registered, IDs associated to data node identifiers are automatically generated.
> 
>    e.g. draft-ietf-netmod-yang-json-06 page 5
>    for the member-name "foomod:top"
>    the ID associated with the name of the module "foomod" is registered,
>    the ID associated with the data node identifier "top" is auto-generated.

How do you auto-generate data node identifiers? Does the algorithm work with module revisions, augmentations, features, ...?

> To simplify scaling of the registered module names, different approaches have been proposed:
> - Possibility to allocation ranges of IDs (bundle) to developers and SDOs for distributed assignment.
> - Possibility to define a range of private IDs (IDs locally assigned 
> and used, not globally unique, same concept as IPv4 10.x.x.x)
> - Possible to define disjoint registries, implemented using a 
> different resource type & default URI path

I need to understand the algorithm for assigning data node identifiers first to see whether this approach makes sense.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
Fax:   [phone]         <http://www.jacobs-university.de/>