Re: [Rtg-yang-coord] comment concerning draft-shaikh-rtgwg-policy-model-00

[Anees Shaikh <[e-mail]>]

Juergen, you're right that prefix-lists in the model turned out to be a bit
problematic as currently defined.  We've updated the model in the most
recent revision after going through some translations of our configs to the
OpenConfig model and running into some issues.  The updated version looks
more like the following:

list prefix {
          key "address masklength masklength-range";

          leaf address {
            type inet:ip-address;
          }

          leaf masklength {
            type uint8;
          }

          leaf masklength-range {
            type string {
              pattern '^([0-9]+\.\.[0-9]+)|exact$';
            }
         }
}

The model used address and a separate masklength so that range checking
could be performed on the mask.   We've since removed the range-checking in
favor of simplifying to keep a single prefix list for both address types,
ipv4 and ipv6.

The original model had the problem you mention, which is that all keys must
be mandatory, including masklength-range, which meant there was no simple
way to express an exact prefix other than, e.g., 21..21 which we didn't
think was desirable.  Changing the masklength-range to a string allows a
more flexible pattern (including an 'exact' setting).  The masklength-range
is included in the keys to make the list have unique members.

I think we could also consider your suggestion to use a inet:ip-prefix
instead of address since we're not doing range-checking on the masklength
in the current approach -- will discuss with the co-authors.

Agree with your suggestion to make the XML examples more conformant (they
should certainly validate), though we've only been using ad-hoc namespaces
for models that are not IETF WG models so far.  My understanding is that
this is the recommended practice.

thanks.
-- Anees


On Wed, May 27, 2015 at 5:24 AM, Juergen Schoenwaelder <
[e-mail]> wrote:

> Hi,
>
> I have read the document and I have a small comment.
>
> - You define a list 'prefix' in the list 'prefix-set' which is keyed
>   by three leafs. As a result, all three leafs are mandatory. Your XML
>   instance snipped in section 10 does not validate because it is
>   missing mandatory key elements. I wonder (a) why did you not use
>   inet:ip-prefix instead of the pair inet:ip-address and a unit8
>   masklength. And given the desire to represent a prefix range, would
>   a special syntax not make sense, e.g. an extension of ip-prefix,
>   lets call it ip-prefix-range, that allows to express a range of
>   prefixes:
>
>   10.3.192.0/21-24 -> 10.3.192.0/21
>                       10.3.192.0/22
>                       10.3.192.0/23
>                       10.3.192.0/24
>
>   If the '-24' part is made optional, your prefix list will be
>   collapsed to a simple
>
>   list prefix {
>       key prefix-range;
>
>       leaf prefix-range {
>           type ip-prefix-range;
>       }
>   }
>
>   Such an ip-prefix-range type may even be a useful addition to
>   ietf-inet-types.
>
> - The XML snippets are nice but it would be cool if they were using
>   proper namespaces and validate against the data model. Perhaps
>   something to consider for -01. The pyang tutorial provides examples
>   how to validate XML snippets against YANG definitions.
>
> /js
>
> --
> Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
> Fax:   [phone]         <http://www.jacobs-university.de/>
>
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