YANG-CBOR: Allocating SID ranges for PEN holders

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Table of Contents

1. Introduction

YANG-CBOR [RFC9254] defines YANG Schema Item iDentifiers (YANG SID), globally unique 63-bit unsigned integers used to identify YANG items. [RFC9595] defines ways to allocate these SIDs on the basis of IANA registries.¶

The present specification employs these SID allocation mechanisms to allocate ranges with 100 000 SIDs (representation size 64 bits) each for each of the holders of IANA-registered Private Enterprise Numbers (PENs) < 1 000 000, as well as ranges with 10 000 SIDs (representation size 32 bits) each for each of the holders of PENs < 100 000.¶

IANA [is requested to allocate/has allocated] a mega-range with 100 billion SIDs (representation size 64 bits), for the SID numbers 300 000 000 000 to 399 999 999 999.¶

IANA also [is requested to allocate/has allocated] a mega-range with 1 billion SIDs (representation size 32 bits), for the SID numbers 3 000 000 000 to 3 999 999 999.¶

Private Enterprise Numbers (PENs) are registered in [IANA.enterprise-numbers] in a low-threshold, low-overhead registration process. At the time of writing (~ 37 years after creating this registry), around 65 000 PENs are registered. In this document, the registrant for a PEN is referred to as the "PEN holder".¶

The present specification makes the following SID ranges available to certain (current or future) PEN holders for allocation in a scheme defined by the holder:¶

• The holder of a PEN ppp ppp (< 1 000 000) can use the SID numbers 3pp ppp p00 000 to 3pp ppp p99 999.¶

• The holder of a PEN pp ppp (< 100 000) can also use the smaller SID numbers 3 ppp pp0 000 to 3 ppp pp9 999.¶

2. Example

[RFC5612] has allocated Enterprise Number 32473 "for use in examples in RFCs, books, documentation, and the like".¶

If this Enterprise Number had an actual PEN holder, the present specification would confer control to it over the SID ranges:¶

• 303 247 300 000 up to 303 247 399 999, and¶

• 3 324 730 000 up to 3 324 739 999.¶

(The plaintext form of this document shows "*" characters around the digits conveying the PEN, which are shown in boldface in the typographic forms.)¶

As Enterprise Number 32473 is intended to be used in documentation, the SIDs in the two SID ranges listed here for the documentation PEN are consequently also available for use in documentation.¶

3. Discussion

This allocation provides an extremely-low-threshold (zero-interaction) way for PEN holders to get number space for the YANG SIDs used in their YANG modules. If a PEN is not already available to the entity needing such number space, it can be obtained in a very low-threshold process. Employing this number space is, however, not always the approach to recommend to a module author:¶

• In the larger of the two spaces, each SID number needs a representation size of 64 bits ("64-bit SIDs"). (This larger representation size of the absolute value of the SID is of comparatively little consequence due to the delta-encoding used for SIDs in YANG-CBOR.)¶

• For the holders of PENs < 100 000, there additionally is a smaller space where each SID number needs a representation size of 32 bits ("32-bit SIDs"). PEN numbers that have access to this space (PEN < 100 000) are likely to run out before or around 2040; the expectation is that by that time there will be enough opportunities to request SID ranges within mega-ranges allocated by other registrants that this mechanism is less needed.¶

• This space has no infrastructure to discover the YANG module behind a SID. Of course, each PEN holder can provide such infrastructure, but even then the problem remains of how to find that infrastructure for a SID. (Search engines may mitigate this somewhat.) On the other hand, in some cases this relative obscurity may be exactly what a PEN holder wants to achieve by using this mechanism.¶

  If obscurity is not the intention, one or both of the following approaches are encouraged:¶

  • The PEN holder can provide a public repository where their YANG models can be found alongside the applicable SID files. Such a repository may be easy to set up using a popular git forge such as, at the time of writing, GitHub.¶

  • Implementations that employ PEN-based SIDs can facilitate information discovery by providing [I-D.ietf-core-yang-library] or another form of YANG library [RFC8525].¶

Relying on the PEN registry might theoretically trigger a land-grab by prospective writers of YANG modules. However, PENs have been around for decades (see Section 3.1.4 of [RFC1065], which continues to be in force with no technical changes as Section 3.1.4 of RFC 1155 [STD16]), and such a land-grab has not occurred for the other allocations implicitly provided by obtaining a PEN.¶

4. IANA Considerations

RFC Ed.: throughout this section, please replace RFC-XXXX with the RFC number of this specification and remove this note.¶

As per Section 6.3 of [RFC9595], in the "YANG-SID Mega-Ranges" registry within the "YANG SIDs" registry group [IANA.yang-sid], this document allocates two mega-ranges, one with 1 billion SIDs ranging from 3 000 000 000 up to 3 999 999 999 (32-bit representation size), and one with 100 billion SIDs ranging from 300 000 000 000 up to 399 999 999 999 (64-bit representation size), as summarized in Table 1.¶

IANA is requested to mark the following ranges as reserved for documentation:¶

• 303 247 300 000 up to 303 247 399 999¶

• 3 324 730 000 up to 3 324 739 999¶

An additional contact for the allocation is: IETF CORE Working Group (core@ietf.org) or IETF Applications and Real-Time Area (art@ietf.org).¶

The allocation policy inside the mega-range is "private" (see Section 6.3.2 of [RFC9595]). The URL is that of the present specification.¶

The management of the SID block of 100 000 SIDs each, ranging from 3pp ppp p00 000 to 3pp ppp p99 999, is delegated to the PEN holder for PEN ppp ppp (i.e., the PEN holder for ppp ppp controls SID 3pp ppp p00 000 to 3pp ppp p99 999).¶

Similarly, the management of the SID block of 10 000 SIDs each, ranging from 3 ppp pp0 000 to 3 ppp pp9 999, is delegated to the PEN holder for PEN pp ppp (i.e., the PEN holder for pp ppp controls SID 3 ppp pp0 000 to 3 ppp pp9 999).¶

Section 6.3.2 of [RFC9595] requires an organization that requests an entry in the "YANG-SID Mega-Ranges" registry to ensure the technical capacity to manage the SID ranges within those mega-ranges for a period of at least 10 years (Private ranges). The individual SID ranges within the mega-ranges allocated in this document are assigned through the registration of PEN numbers. The technical capacity to ensure the sustained operation of the PEN number registry is derived from the demonstrated capacity of IANA to maintain this registry as well as the importance of a functioning PEN number registry in other contexts.¶

5. Security Considerations

Section 5 (Security Considerations) of [RFC9595] applies, as well as Section 8 (Security Considerations) of [RFC9254]. In particular, the fact that a certain Private Enterprise Number appears in a SID is not an indicator of provenance, i.e., it does not guarantee that the SID or underlying YANG model actually does originate from the holder of that PEN. The requirement to ascertain the authoritative source of this information, as discussed in the above security considerations, remains.¶

6. References

Acknowledgments

This document was inspired by the discussion of the authors of [RFC9254] and [RFC9595] on how to handle Rob Wilton's feedback.¶

Author's Address