Thanks a lot Acee, Now that knowing it is backwards compatible, are you ok in the update of the model?
Also, In order to update the YANG model, instead of going to a bis, which for a "small" backwards compatible change might be now a bit of overhead, I have seen that in opsawg Med has proposed VELOCE (see https://datatracker.ietf.org/meeting/124/materials/slides-124-opsawg-yang-develpment-process-maintenance-veloce-01 ). It was presented as a light process to update yang models that require small changes and it is requesting volunteers for experiments. Would you and the working group be willing to experiment on VELOCE making the update in this way rather than directly creating a bis? It can also help in future upgrades of other Yang models in the working group. Best Regards, Oscar ________________________________ De: Acee Lindem <[email protected]> Enviado: Martes, 27 de Enero de 2026 14:46 Para: OSCAR GONZALEZ DE DIOS <[email protected]> CC: [email protected] <[email protected]> Asunto: Re: [rtgwg] Update Routing Policy Yang (RFC 9067) model to represent 0.0.0.0/0 exact (mask-lenght-lower 0 and upper-length-lower 0))? AVISO/WARNING: Este correo electrónico se originó desde fuera de la organización. No haga clic en enlaces ni abra archivos adjuntos a menos que reconozca al remitente y sepa que el contenido es seguro / This email has been originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. At least ChatGTP agrees this is backward compatible: In YANG (RFC 7950), loosening a constraint is backward compatible, while tightening a constraint is not. Changing the range from: uint8 { range "1..128"; } to: uint8 { range "0..128"; } expands the set of valid values by adding 0. That means: * All values that were valid before (1..128) are still valid * Existing clients that send values in the old range will continue to work * Existing servers that produced values in the old range are still compliant So this is a relaxation, not a restriction. How RFC 7950 views this RFC 7950 treats changes as backward compatible if they do not invalidate previously valid data. Expanding a range (or length, pattern, etc.) fits that rule. Practical caveats (worth keeping in mind) While it’s backward compatible per YANG rules, you should still consider: * Semantic meaning: If 0 has special meaning (e.g., “unset”, “disabled”), clients may not expect it. * Defaults: If the leaf has a default, adding 0 doesn’t change behavior unless the default is changed. * Client assumptions: Some clients may implicitly assume >=1 even if the model didn’t strictly guarantee it — that’s a client bug, but it happens. Summary ✅ Backward compatible in YANG 1.1 ❌ Not backward compatible would be something like 1..128 → 10..128 If you want, I can also walk through how this affects semantic versioning, deviation handling, or client/server upgrade scenarios. Is this conversation helpful so far? On Jan 27, 2026, at 8:42 AM, Acee Lindem <[email protected]> wrote: Hi Oscar, It would seem otherwise be a backward compatible change since the range is less restrictive but would require a BIS version of the document. Thanks, Acee On Jan 27, 2026, at 8:22 AM, OSCAR GONZALEZ DE DIOS <[email protected]> wrote: Dear RTWG colleagues and RFC 9067 authors, The yang model in 9067 allows to represent a prefix range list with ip-prefix and a mask-lenght-lower and upper in each entry of the list. While using the model to reconcile all the prefix-lists in my company's networks I found that it was not possible to represent one corner case the exact 0.0.0.0/0 (or the equivalent ::/0 in IPv6) . It would be ip-prefix 0.0.0.0/0 mask-lenght-lower 0 and upper-length-lower 0, but unfortunately in the model mask-length-upper needs to be at least 1 (cannot be 0). Would it be feasible to update the yang model to allow the mask-length-upper to start with 0 and cover this use case (found in operational networks)? Please find below the tree and current definition. | | +--rw prefixes | | +--rw prefix-list* [ip-prefix mask-length-lower | | mask-length-upper] | | +--rw ip-prefix inet:ip-prefix | | +--rw mask-length-lower uint8 | | +--rw mask-length-upper uint8 leaf mask-length-upper { type uint8 { range "1..128"; } must '../mask-length-upper >= ../mask-length-lower' { error-message "The upper bound MUST NOT be less " + "than lower bound."; } description "Mask length range upper bound. It MUST NOT be less than lower bound."; } } Best Regards, Oscar Gonzalez de Dios Technical Lead for SDN in Transport Networks Telefonica CTIO Transport Network Unit <Outlook-hdzxtpb2.png> ________________________________ Este mensaje y sus adjuntos se dirigen exclusivamente a su destinatario, puede contener información privilegiada o confidencial y es para uso exclusivo de la persona o entidad de destino. 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Esta mensagem e seus anexos se dirigem exclusivamente ao seu destinatário, pode conter informação privilegiada ou confidencial e é para uso exclusivo da pessoa ou entidade de destino. Se não é vossa senhoria o destinatário indicado, fica notificado de que a leitura, utilização, divulgação e/ou cópia sem autorização pode estar proibida em virtude da legislação vigente. Se recebeu esta mensagem por erro, rogamos-lhe que nos o comunique imediatamente por esta mesma via e proceda a sua destruição _______________________________________________ rtgwg mailing list -- [email protected]<mailto:[email protected]> To unsubscribe send an email to [email protected]<mailto:[email protected]> ________________________________ Este mensaje y sus adjuntos se dirigen exclusivamente a su destinatario, puede contener información privilegiada o confidencial y es para uso exclusivo de la persona o entidad de destino. 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