Re: [yang-doctors] Small modules discussion from LSR [Fwd: [Lsr] When to augment LSR base YANG modules...]

"Acee Lindem (acee)" <acee@cisco.com> Tue, 02 April 2019 12:11 UTC

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From: "Acee Lindem (acee)" <acee@cisco.com>
To: Martin Bjorklund <mbj@tail-f.com>, "Rob Wilton (rwilton)" <rwilton@cisco.com>
CC: "yang-doctors@ietf.org" <yang-doctors@ietf.org>, "yingzhen.qu@huawei.com" <yingzhen.qu@huawei.com>
Thread-Topic: [yang-doctors] Small modules discussion from LSR [Fwd: [Lsr] When to augment LSR base YANG modules...]
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Date: Tue, 2 Apr 2019 12:11:48 +0000
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Subject: Re: [yang-doctors] Small modules discussion from LSR [Fwd: [Lsr] When to augment LSR base YANG modules...]
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Hi Martin, 

On 4/2/19, 7:29 AM, "yang-doctors on behalf of Martin Bjorklund" <yang-doctors-bounces@ietf.org on behalf of mbj@tail-f.com>; wrote:

    "Rob Wilton (rwilton)" <rwilton@cisco.com>; wrote:
    > 
    > 
    > > -----Original Message-----
    > > From: Christian Hopps <chopps@chopps.org>;
    > > Sent: 02 April 2019 11:31
    > > To: Rob Wilton (rwilton) <rwilton@cisco.com>;
    > > Cc: Christian Hopps <chopps@chopps.org>;; YANG Doctors <yang-
    > > doctors@ietf.org>;; Yingzhen Qu <yingzhen.qu@huawei.com>;
    > > Subject: Re: [yang-doctors] Small modules discussion from LSR [Fwd:
    > > [Lsr]
    > > When to augment LSR base YANG modules...]
    > > 
    > > 
    > > > On Apr 2, 2019, at 5:52 AM, Rob Wilton (rwilton) <rwilton@cisco.com>;
    > > wrote:
    > > >
    > > > Hi Chris,
    > > >
    > > > I don’t think that there is a one size fits all answer here.
    > > >
    > > > If the enhancement is small, and is likely to be reasonably widely
    > > > used then
    > > my view is that adding it as an optional feature to the base module is
    > > a better
    > > choice in the long term.
    > > >
    > > > If the feature is larger, or esoteric, and perhaps won’t be widely
    > > > deployed
    > > then I would think that putting it into a separate module might be a
    > > better
    > > choice.
    > > >
    > > > I actually think that it is the IETF process that is perhaps the
    > > > difficult thing
    > > here.  I.e. I think that you want to republish a new revision of the
    > > base
    > > module, but in a way that gets processed more quickly by the IESG.
    > > E.g.
    > > request that they only review/comment on the diffs between the current
    > > revision and the previous one.  Or somehow publish an updated revision
    > > of
    > > the module on github without assigning it a new RFC number every time.
    > > 
    > > Yes, although I'm trying to do a couple things:
    > > 
    > > - Get YANG management support added at the same time as the
    > > functionality, not as an after thought maybe someday, maybe never.
    > 
    > I agree that this is definitely the right thing to do.
    > 
    > 
    > > - Reduce the cost of adding the YANG support. A stand-alone document is
    > > very expensive time and effort wise, separate IESG reviews,
    > > directorate
    > > reviews, last-calls.
    > 
    > I agree.  And rev'ing the base ISIS YANG model is likely to be just as
    > expensive.
    
    My suggestion was not to rev the base model, but have _one_ model with
    these "optional features", and rev that every time.

The alternative to individual modules we had discussed is to "batch" these features in a single document. However, once published, we'd start on the next set of optional features. 

From a programmability standpoint, which is preferred option? Are they all pretty much the same level of complexity? 

Thanks,
Acee




    
    > > I had wondered if we could use errata on the base vs doing a brand new
    > > bis
    > > version of the base module; however, this seems to be trading too much
    > > process overhead with perhaps not quite enough.
    > > 
    > > To the first goal, I wrote that reverse metric module a couple days
    > > ago as an
    > > example. I have to wonder when or even if it would have gotten written
    > > (or
    > > the equivalent feature added) otherwise. Instead I suspect it would
    > > just get
    > > added into N vendors models as people move on to other things in the
    > > WG.
    > > 
    > > In a perfect world I would add a YANG section to my functionality RFC
    > > that
    > > updated (not augment) the base module, but with augment style
    > > definition
    > > (i.e., so the entire huge base module doesn't need to be
    > > re-represented in
    > > the document). This would then cause the base document to get reissued
    > > with the changes. Sort of like IANA sections are capable of updating a
    > > registry.
    > 
    > We almost want to just include a diff/patch to the base model into the
    > document.  This is actually a little bit like how IEEE 802 update
    > their documents, and then they periodically roll their updates into
    > the base model.
    > 
    > 
    > > 
    > > So maybe your github idea is like this, we create a module definition
    > > registry
    > > where the most up-to-date module definitions go, and then RFCs can
    > > update
    > > that using something like (or exactly like) augment to document the
    > > changes
    > > to the module in the individual RFCs.
    > 
    > Yes.  We want the review to only focus on the stuff that is new/added
    > rather than reviewing the whole module every time.
    > 
    > Martin's suggestion of using submodules is another way to achieve
    > this.  E.g. the actual module definition is split over multiple RFCs,
    > but I'm not that keen on submodules and I suspect that this will make
    > them hard to read in future.
    
    Note that we can "gc" the submodules and fold their contents into the
    main module, or perhaps a "top" submodule, when you have N submodules.
    
    
    > I think that the real answer here is that YANG modules should not be
    > published in RFCs.  Yes, they should go through a similar formal
    > review process for changes to the modules but without the overhead of
    > reviewing every change as a new document.
    
    Right.  This is longer term though, since it requires a process
    update!
    
    
    /martin
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