Re: [netmod] Y34 - root node

[Juergen Schoenwaelder <[e-mail]>]

On Wed, Aug 26, 2015 at 05:41:29PM +0100, t. petch wrote:
> ----- Original Message -----
> From: "Juergen Schoenwaelder" <[e-mail]>
> To: "t. petch" <[e-mail]>
> Cc: <[e-mail]>; "Martin Bjorklund" <[e-mail]>;
> <[e-mail]>
> Sent: Sunday, August 23, 2015 6:04 PM
> 
> > On Wed, Aug 19, 2015 at 05:24:41PM +0100, t. petch wrote:
> >
> > > The current model is a flat architecture of hundreds (or thousands)
> of
> > > modules each with their own top level nodes, namespace, namespace
> name,
> > > prefix etc.  (This is quite different to SMI with its hierarchy but
> that
> > > probably is only significant to those who have spent 20 years with
> SMI).
> >
> > This is most likely a wrong perception. There are basically only two
> > locations where SNMP modules are registered in the IETF: under mib-2
> > and under transmission (yes there are a few exceptions but overall in
> > number they do not matter). There are close to 240 MIB modules below
> > mib-2 and about 50 MIB modules below transmission.
> 
> Juergen
> 
> I know what you mean, that the MIB module tree is somewhat fasciated,
> but there is still one root, from which an obvious, absolute OID can be
> used to identify uniquely any MIB module (or in some contexts a
> relative one, relative to transmission or mib 2).  If SMI did have
> constraints, then there would not be an issue of how to express them,
> nor would there be any question of mounting a module elsewhere for
> whatever
> reason (which then creates problems for the references in the
> constraints).

While SMIv2 does not have something like MUST and WHEN expressions, it
still does have references between model elements. Prime example:
ifTabel got augmented by ifXTable registered in a very different
location. It is a major mis-conception that the OID tree is relevant;
what is relevant are relationships between conceptual tables.

> A flat sea of YANG modules is different; I haven't counted lately
> how many top level nodes I have seen but it is a lot and when I see
> people wanting to organise YANG modules into a tree, I wonder if
> they are trying to recreate an SMI-like tree and my reaction is that
> this is not SMI!

There is no point in organizing them into a tree. There simply is no
universal forever stable tree. When SMIv2 started, people thought such
a tree would evolve and it was later recognized that this is an
illusion and we ended up registering almost everything under mib-2 or
transmission.

> The flat sea of YANG modules brings a different set of issues and I
> am unsure what they are;

This is main problem I have. What the heck is the problem we are trying
to fix?

> I understand what is involved with the references in constraints, I
> can see that there will be a lot of namespaces and prefixes and can
> speculate about what that will bring but what it means to have so
> many top level nodes, I do not know.

Having 200+ MIB modules registered below mib-2 has not been a problem
as far as I know.

/js

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