Re: [netmod] [Lsr] I-D Action: draft-ietf-lsr-ospfv3-extended-lsa-yang-10.txt

[Andy Bierman <[e-mail]>]

On Mon, Apr 11, 2022 at 10:07 AM Rob Wilton (rwilton) <rwilton=
[e-mail]> wrote:

> Hi all,
>
> Thanks for the comments on this thread so far.  It would be nice if we are
> able to come to some sort of rough consensus to a solution.
>
> I think that there is consensus that the YANG type ip-address (and the
> v4/v6 versions) are badly named as the prominent default type name has been
> given to the unusual variant of including zone information.
>
> Based on the comments on this thread, it also seems likely to me that most
> of the usages of ip-address in YANG RFCs is likely to be wrong, and the
> intention was that IP addresses without zones was intended.  At a rough
> count, of the published RFC YANG models at github
> YangModels/standard/ietf/RFC/ to be:
>         86 uses of ip-address
>         68 uses of ipv4-address
>         66 uses of ipv6-address
>
>         1 use of ip-address-no-zone
>         4 uses of ipv4-address-no-zone
>         4 uses of ipv6-address-no-zone
>
> These types appear in 49 out of the 141 YANG modules published in RFCs.
> At a quick guess/check it looks like these 49 YANG modules may appear in
> 40-50 RFCs.
>
> As mentioned previously, it is also worth comparing this to the OpenConfig
> YANG modules:
> They have redefined ip-address (and v4/v6 variants) to exclude zone
> information and have defined separate types include zone information.
> There are no explicit uses of the "-zoned" variants of OpenConfig IP
> addresses in the latest OpenConfig github repository.  However,
> approximately a third of the IP address types are still to the
> ietf-inet-types.yang rather than openconfig-inet-types.yang, so in theory
> some of those 58 entries could still intentionally be supporting zoned IP
> addresses, but I would expect that the vast majority would not.
> I do see some strong benefit if this basic type being defined in the same
> way in both IETF and OC YANG, and I believe that the OC folks have got the
> definition right.
>
> I see that some are arguing that the zone in the ip-address definition is
> effectively optional, and implementations are not really obliged to
> implement it.  I don't find that argument compelling, at least not with the
> current definition of ip-address in RFC 6991.  I see a clear difference
> between a type defined with an incomplete regex that may allow some invalid
> values and a type that is explicitly defined to included additional values
> in the allowable value space.  Further, I believe that a client just
> looking at the YANG module could reasonably expect a server that implements
> a data node using ip-address would be expected to support IP zones, where
> they are meaningful, or otherwise they should deviate that data node to
> indicate that they don't conform to the model.
>
> We also need to be realistic as to what implementations will do.  They are
> not going to start writing code to support zones just because they are in
> the model.  They will mostly reject IP addresses with zone information.
> Perhaps some will deviate the type to ip-address-no-zone, but probably most
> won't.
>
> The option of respinning approx. 40-50 RFCs to fix this doesn't feel at
> all appealing.  This would take a significant amount of time/effort and I
> think that we will struggle to find folks who are willing to do this.
> Although errata could be used to point out the bug, then can't be used to
> fix it, all the errata would be "hold for document update" at best.
> Further, during the time that it would take us to fix it, it is plausible
> that more incorrect usages of ip-address will likely occur (but perhaps
> could be policed via scripted checks/warnings).
>
>
> I still feel the right long-term solution here is to get to a state where
> the "ip-address" type means what 99% of people expect it to mean, i.e.,
> excluding zone information.
>
> Given the pushback on making a single non-backwards compatible change to
> the new definition, I want to ask whether the following might be a possible
> path that gains wider consensus:
>
> (1) In RFC 6991 bis, I propose that we:
> (i) define new ip-address-with-zone types (and v4 and v6 versions) and
> keep the -no-zone versions.
> (ii) we change the description of "ip-address" to indicate:
> - Although the type allows for zone information, many implementations are
> unlikely to accept zone information in most scenarios (i.e., so the
> description of the type more accurately reflects reality).
> - A new ip-address-with-zone type has been introduced to use where zoned
> IP addresses are required/useful, and models that use ip-address with the
> intention of supporting zoned IP addresses MUST migrate to
> ip-address-with-zone.
> - In the future (at least 2 years after RFC 6991 bis is published), the
> expectation is that the definition of ip-address will change to match that
> of ip-address-no-zone.
>
> (2) Then in 2 years time, we publish RFC 6991-bis-bis to change the
> definition of ip-address to match ip-address-no-zone and deprecate the
> "-no-zone" version at the same time.
>
> My reasoning as to why to take this path is:
> (1) It is a phased migration, nothing breaks, 3rd parties have time to
> migrate.
> (2) It ends up with the right definition (with the added bonus that it
> aligns to the OC definition).
> (3) It doesn't require us republishing 40+ RFCs.
> (4) it hopefully allows us to use YANG versioning to flag this as an NBC
> change, along with the other standards to help mitigate this change (import
> revision-or-derived, YANG packages, schema comparison).
>
> I would be keen to hear thoughts on whether this could be a workable
> consensus solution - i.e., specifically, you would be able to live with it.
>
>

This is a very thoughtful proposal. Looks good to me.

It does introduce a window in which some new modules might start using
'ip-address-no-zone'.
Should they wait for the real 'ip-address' in 2 more years or just use
'ip-address-no-zone'?

The leaf description-stmt using 'ip-address' should specify if any zone
support is required.
The default could be 'none' so no mention is needed most of the time.






> Regards,
> Rob
>
>
>
Andy


>
> > -----Original Message-----
> > From: netmod <[e-mail]> On Behalf Of Randy Presuhn
> > Sent: 08 April 2022 18:59
> > To: Christian Hopps <[e-mail]>
> > Cc: [e-mail]; [e-mail]
> > Subject: Re: [netmod] [Lsr] I-D Action:
> draft-ietf-lsr-ospfv3-extended-lsa-
> > yang-10.txt
> >
> > Hi -
> >
> > On 2022-04-08 5:11 AM, Christian Hopps wrote:
> > ..
> > > Instead, Acee (I'm not sure I'd call him WG B :) is asserting that
> > > *nobody* actually wanted the current type, and it has been misused
> > > everywhere and all over. The vast majority of implementations in
> > > operation probably can't even handle the actual type (Andy's point).
> So,
> > > Acee is just the messenger of bad news here. Please note that the AD in
> > > charge of all this agreed with Acee as well.
> >
> > That's not the impression one gets from modules like
> > https://www.ietf.org/archive/id/draft-ietf-mpls-mldp-yang-10.txt
> > which employs both types.  So, regardless of whether one is willing
> > to respect YANG's compatibility rules, it's no longer a matter of
> > speculation whether a name change would cause actual damage -
> > it clearly would.  Furthermore, my recollection is that the
> > WG *did* discuss whether the "zonable" property was needed, so
> > any argument based on the assertion that "*nobody* actually
> > wanted the current type" seems to me to based on a false premise.
> >
> > Randy
> >
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