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

["Joel M. Halpern" <[e-mail]>]

Do we have reason to believe that no one outside the IETF has used 
ip-address as we published in ways that need a zone?

It seems to me that the first step in the plan below is reasonable.  But 
changing ip-address itself seems a bad idea.  If one means no-zone, use 
the -no-zone typedef.

Yours,
Joel

On 4/11/2022 1:28 PM, Andy Bierman wrote:
> 
> 
> On Mon, Apr 11, 2022 at 10:07 AM Rob Wilton (rwilton) 
> <rwilton=[e-mail] <mailto:[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]
>     <mailto:[e-mail]>> On Behalf Of Randy Presuhn
>      > Sent: 08 April 2022 18:59
>      > To: Christian Hopps <[e-mail] <mailto:[e-mail]>>
>      > Cc: [e-mail] <mailto:[e-mail]>; [e-mail]
>     <mailto:[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
>     <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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