Guidelines and Registration Procedures for Interface Types and Tunnel Types
draft-thaler-iftype-reg-07
The information below is for an old version of the document that is already published as an RFC.
Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8892.
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Authors | Dave Thaler , Dan Romascanu | ||
Last updated | 2020-08-28 (Latest revision 2020-01-16) | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
Intended RFC status | Proposed Standard | ||
Formats | |||
Reviews |
GENART Last Call review
(of
-06)
by Peter Yee
Ready w/nits
TSVART Last Call review
(of
-05)
by Tommy Pauly
Ready w/nits
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Stream | WG state | (None) | |
Document shepherd | Ian Farrer | ||
Shepherd write-up | Show Last changed 2019-09-30 | ||
IESG | IESG state | Became RFC 8892 (Proposed Standard) | |
Action Holders |
(None)
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Consensus boilerplate | Yes | ||
Telechat date | (None) | ||
Responsible AD | Suresh Krishnan | ||
Send notices to | (None) | ||
IANA | IANA review state | IANA - Not OK | |
IANA action state | RFC-Ed-Ack |
draft-thaler-iftype-reg-07
Network Working Group D. Thaler Internet-Draft Microsoft Updates: 2863 (if approved) D. Romascanu Intended status: Best Current Practice Independent Expires: July 19, 2020 January 16, 2020 Guidelines and Registration Procedures for Interface Types and Tunnel Types draft-thaler-iftype-reg-07 Abstract This document provides guidelines and procedures for those who are defining, registering, or evaluating definitions of new interface types ("ifType" values) and tunnel types. The original definition of the IANA interface type registry predated the use of IANA Considerations sections and YANG modules, and so some confusion arose over time. Tunnel types were added later, with the same requirements and allocation policy as interface types. This document updates RFC 2863, and provides updated guidance for these registries. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on July 19, 2020. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Thaler & Romascanu Expires July 19, 2020 [Page 1] Internet-Draft ifType Guidelines January 2020 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Problems . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Interface Sub-Layers and Sub-Types . . . . . . . . . . . . . 4 4.1. Alternate Values . . . . . . . . . . . . . . . . . . . . 5 5. Available Formats . . . . . . . . . . . . . . . . . . . . . . 6 6. Registration . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Procedures . . . . . . . . . . . . . . . . . . . . . . . 7 6.2. Media-specific OID-subtree assignments . . . . . . . . . 8 6.3. Registration Template . . . . . . . . . . . . . . . . . . 8 6.3.1. ifType . . . . . . . . . . . . . . . . . . . . . . . 8 6.3.2. tunnelType . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7.1. MIB and YANG Modules . . . . . . . . . . . . . . . . . . 11 7.2. Transmission Number Assignments . . . . . . . . . . . . . 12 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . . 12 9.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 1. Introduction The IANA IfType-MIB, which contains the list of interface type (ifType) values, was originally defined in [RFC1573] as a separate MIB module together with the Interfaces Group MIB (IF-MIB) module. The IF-MIB module was subsequently updated and is currently specified in [RFC2863], but this latest IF-MIB RFC no longer contains the IANA IfType-MIB. Instead, the IANA IfType-MIB is maintained by IANA as a separate module. Similarly, [RFC7224] created an initial IANA Interface Type YANG Module, and the current version is maintained by IANA. The current IANA IfType registry is at [ifType-registry], with the same values also appearing in both [yang-if-type] and the IANAifType textual convention at [IANAifType-MIB]. Although the ifType registry was originally defined in a MIB module, the assignment and use of interface type values are not tied to MIB modules or any other management mechanism. An interface type value Thaler & Romascanu Expires July 19, 2020 [Page 2] Internet-Draft ifType Guidelines January 2020 can be used as the value of a data model object (MIB object, YANG object, etc.), or as part of a unique identifier of a data model for a given interface type (e.g., in an OID), or simply as a value exposed by local APIs or UI on a device. The TUNNEL-MIB was defined in [RFC2667] (now obsoleted by [RFC4087]) which created a tunnelType registry ([tunnelType-registry] and the IANAtunnelType textual convention at [IANAifType-MIB]) and defined the assignment policy for tunnelType values to always be identical to the policy for assigning ifType values. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. Problems This document addresses the following issues: 1. As noted in Section 1, the original guidance was written with wording specific to MIB modules, and accordingly some confusion has resulted when using YANG modules. This document clarifies that ifTypes and tunnelTypes are independent from the type of, or even existence of, a data model. 2. The use of and requirements around sub-layers and sub-types were not well understood, but good examples of both now exist. This is discussed in Section 4. 3. Since the ifType and tunnelType registries were originally defined, and are still retrievable, in the format of MIB modules (in addition to other formats), confusion arose when adding YANG modules as another format, as to whether each is a separate registry. This is discussed in Section 5. 4. The registries are retrievable in the format of MIB and YANG modules, but there was previously no process guidance written to check that those formats were syntactically correct as updates were made, which led to the registry having syntax errors that broke tools. Section 6.1 adds a validation step to the documented assignment procedure. 5. Various documents and registries previously said to submit requests via email, but a web form exists for submitting Thaler & Romascanu Expires July 19, 2020 [Page 3] Internet-Draft ifType Guidelines January 2020 requests, which caused some confusion around which was to be used. This is addressed in Section 6.1. 6. Transmission values [transmission-registry] have generally been allocated as part of ifType allocation, but no guidance existed as to whether a requester must ask for it or not, and the request form had no such required field. As a result, IANA has asked the Designated Expert to decide for each allocation, but no relevant guidance for the Designated Expert has been documented. This is remedied in Section 6.2. 4. Interface Sub-Layers and Sub-Types When multiple sub-layers exist below the network layer, each sub- layer can be represented by its own row in the ifTable with its own ifType, with the ifStackTable being used to identify the upward and downward multiplexing relationships between rows. Section 3.1.1 of [RFC2863] provided more discussion, and Section 3.1.2 of that RFC provided guidance for defining interface sub-layers. More recent experience shows that those guidelines were phrased in a way that is now too restrictive, since at the time [RFC2863] was written, MIB modules were the dominant data model. This document clarifies that the same guidance also applies to YANG modules. Some ifTypes may define sub-types. For example, the tunnel(131) ifType defines sub-types, where each tunnelType can have its own MIB and/or YANG module with protocol-specific information, but there is enough in common that some information is exposed in a generic IP Tunnel MIB corresponding to the tunnel(131) ifType. For requests that involve multiple sub-layers below the network layer, requests MUST include (or reference) a discussion of the multiplexing relationships between sub-layers, ideally with a diagram. Various well-written examples exist of such definitions, including [RFC3637] section 3.4.1, [RFC4087] section 3.1.1, and [RFC5066] section 3.1.1. Definers of sub-layers and sub-types should consider which model is more appropriate for their needs. A sub-layer is generally used whenever either a dynamic relationship exists (i.e., which instances layer over which other instances can change over time) or a multiplexing relationship exists with another sub-layer. A sub-type can be used when neither of these are true, but where one interface type is conceptually a subclass of another interface type, as far as a management data model is concerned. Thaler & Romascanu Expires July 19, 2020 [Page 4] Internet-Draft ifType Guidelines January 2020 In general, the intent of an interface type or sub-type is that its definition should be sufficient to identify an interoperable protocol. In some cases, however, a protocol might be defined in a way that is not sufficient to provide interoperability with other compliant implementations of that protocol. In such a case, an ifType definition should discuss whether specific instantiations (or profiles) of behavior should use a sub-layer model (e.g., each vendor might layer the protocol over its own sub-layer that provides the missing details), or a sub-type model (i.e., each vendor might subclass the protocol without any layering relationship). If a sub- type model is more appropriate, then the data model for the protocol might include a sub-type identifier so that management software can discover objects specific to the subtype. In either case, such discussion is important to guide definers of a data model for the more specific information (i.e., a lower sub-layer or a subtype), as well as the Designated Expert that must review requests for any such ifTypes or sub-types. 4.1. Alternate Values Another design decision is whether to reuse an existing ifType or tunnelType value, possibly using a sub-type or sub-layer model for refinements, or to use a different value for a new mechanism. If there is already an entry that could easily satisfy the modeling and functional requirements for the requested entry, it should be reused so that applications and tools that use the existing value can be used without changes. If however, the modeling and functional requirements are significantly different enough such that having existing applications and tools use the existing value would be seen as a problem, a new value should be used. For example, originally different ifType values were used for different flavors of Ethernet (ethernetCsmacd(6), iso88023Csmacd(7), fastEther(62), etc.), typically because they were registered by different vendors. Using different values was, however, seen as problematic because all were functionally similar, and so [RFC3635] then deprecated all but ethernetCsmacd(6). As another example, a udp(8) tunnelType value was defined in [RFC2667] with the description "The value UDP indicates that the payload packet is encapsulated within a normal UDP packet (e.g., RFC 1234)." The Teredo tunnel protocol [RFC4380] was later defined and encapsulates packets over UDP, but the protocol model is quite different between [RFC1234] and Teredo. For example, [RFC1234] supports encapsulation of multicast/broadcast traffic whereas Teredo does not. As such, it would be more confusing to applications and Thaler & Romascanu Expires July 19, 2020 [Page 5] Internet-Draft ifType Guidelines January 2020 tools to represent them using the same tunnel type, and so [RFC4087] defined a new value for Teredo. In summary, definers of new interface or tunnel mechanisms should use a new ifType or tunnelType value rather than reusing an existing value when key aspects such as the header format or the link model (point-to-point, non-broadcast multi-access, broadcast capable multi- access, unidirectional broadcast, etc.) are significantly different from existing values, but reuse the same value when the differences can be expressed in terms of differing values of existing objects other than ifType/tunnelType, in the standard YANG or MIB module. 5. Available Formats Many registries are available in multiple formats. For example, XML, HTML, CSV, and plain text are common formats in which many registries are available. This document clarifies that the [IANAifType-MIB], [yang-if-type], and [yang-tunnel-type] MIB and YANG modules are merely additional formats in which the ifType and tunnelType registries are available. The MIB and YANG modules are not separate registries, and the same values are always present in all formats of the same registry. The confusion stemmed in part from the fact that the IANA "Protocol Registries" [protocol-registries] listed the YANG and MIB module formats separately, as if they were separate registries. However, the entries for the yang-if-type and iana-tunnel-type YANG modules said "See ifType definitions registry." and "See tunnelType registry (mib-2.interface.ifTable.ifEntry.ifType.tunnelType)." respectively, although the entry for the IANAifType-MIB had no such note. Section 7.1 addresses this. 6. Registration The IANA policy (using terms defined in [RFC8126]) for registration is Expert Review, for both interface types and tunnel types. The role of the Designated Expert in the procedure is to raise possible concerns about wider implications of proposals for use and deployment of interface types. While it is recommended that the responsible Area Director and the IESG take into consideration the Designated Expert opinions, nothing in the procedure empowers the Designated Expert to override properly arrived-at IETF or working group consensus. Thaler & Romascanu Expires July 19, 2020 [Page 6] Internet-Draft ifType Guidelines January 2020 6.1. Procedures Someone wishing to register a new ifType or tunnelType value MUST: 1. Check the IANA registry to see whether there is already an entry that could easily satisfy the modeling and functional requirements for the requested entry. If there is already such an entry, use it or update the existing specification. Text in an Internet-Draft, or part of some other permanently available, stable specification may be written to clarify the usage of an existing entry or entries for the desired purpose. 2. Check the IANA registry to see whether there is already some other entry with the desired name. If there is already an unrelated entry under the name, choose a different name. 3. Prepare a registration request using the template specified in Section 6.3. The registration request can be contained in an Internet-Draft, submitted alone, or as part of some other permanently available, stable specification. The registration request can also be submitted in some other form (as part of another document or as a stand-alone document), but the registration request will be treated as an "IETF Contribution" under the guidelines of [RFC5378]. 4. Submit the registration request (or pointer to a document containing it) to IANA at iana@iana.org or (if requesting an ifType) via the web form at <https://www.iana.org/form/iftype>. Upon receipt of a registration request, the following steps MUST be followed: 1. IANA checks the submission for completeness; if required information is missing or any citations are not correct, IANA will reject the registration request. A registrant can resubmit a corrected request if desired. 2. IANA requests Expert Review of the registration request against the corresponding guidelines from this document. 3. The Designated Expert will evaluate the request against the criteria. 4. Once the Designated Expert approves registration, IANA updates [ifType-registry], [IANAifType-MIB], and [yang-if-type] to show the registration for an interface type, or [tunnelType-registry], [IANAifType-MIB], and [yang-tunnel-type] to show the registration for a tunnel type. When adding values, IANA should verify that Thaler & Romascanu Expires July 19, 2020 [Page 7] Internet-Draft ifType Guidelines January 2020 the updated MIB module and YANG module formats are syntactically correct before publishing the update. There are various existing tools or web sites that can be used to do this verification. 5. If instead the Designated Expert does not approve registration (e.g., for any of the reasons in [RFC8126] section 5), a registrant can resubmit a corrected request if desired, or the IESG can override the Designated Expert and approve it per the process in Section 3.3 of [RFC8126]. 6.2. Media-specific OID-subtree assignments [IANAifType-MIB] notes: The relationship between the assignment of ifType values and of OIDs to particular media-specific MIBs is solely the purview of IANA and is subject to change without notice. Quite often, a media-specific MIB's OID-subtree assignment within MIB-II's 'transmission' subtree will be the same as its ifType value. However, in some circumstances this will not be the case, and implementors must not pre-assume any specific relationship between ifType values and transmission subtree OIDs. The advice above remains unchanged, but this document changes the allocation procedure to streamline the process, so that an ifType value and a transmission number value with the same value will be assigned at the same time. Rationale: (1) This saves effort in the future since if a transmission number is later needed, no IANA request is needed that would then require another Expert Review. (2) The transmission numbering space is not scarce, so there seems little need to reserve the number for a different purpose than what the ifType is for. (3) The Designated Expert need not review whether a transmission number value should be registered when processing each ifType request, thus reducing the possibility of delaying assignment of ifType values. (4) There is no case on record where allocating the same value could have caused any problem. 6.3. Registration Template 6.3.1. ifType The following template describes the fields that MUST be supplied in a registration request suitable for adding to the ifType registry: Label for IANA ifType requested: As explained in Section 7.1.1 of [RFC2578], a label for a named-number enumeration must consist of Thaler & Romascanu Expires July 19, 2020 [Page 8] Internet-Draft ifType Guidelines January 2020 one or more letters or digits, up to a maximum of 64 characters, and the initial character must be a lower-case letter. (However, labels longer than 32 characters are not recommended.) Note that hyphens are not allowed. Name of IANA ifType requested: A short description (e.g., a protocol name), suitable to appear in a comment in the registry. Description of the proposed use of the IANA ifType: Requesters MUST include answers, either directly or via a link to some document with the answers, to the following questions in the explanation of the proposed use of the IANA IfType: o How would IP run over your ifType? o Would there be another interface sublayer between your ifType and IP? o Would your ifType be vendor-specific or proprietary? (If so, the label MUST start with a string that shows that. For example, if your company's name or acronym is xxx, then the ifType label would be something like xxxSomeIfTypeLabel.) o Would your ifType require or allow vendor-specific extensions? If so, would the vendor use their own ifType in a sub-layer below the requested ifType, or a sub-type of the ifType, or some other mechanism? Reference, Internet-Draft, or Specification: A link to some document is required. Additional information or comments: Optionally any additional comments for IANA or the Designated Expert. 6.3.2. tunnelType Prior to this document, no form existed for tunnelType (and new tunnelType requests did not need to use the ifType form that did exist). This document therefore specifies a tunnelType form. The following template describes the fields that MUST be supplied in a registration request suitable for adding to the tunnelType registry: Label for IANA tunnelType requested: As explained in Section 7.1.1 of [RFC2578], a label for a named-number enumeration must consist of one or more letters or digits, up to a maximum of 64 characters, and the initial character must be a lower-case letter. Thaler & Romascanu Expires July 19, 2020 [Page 9] Internet-Draft ifType Guidelines January 2020 (However, labels longer than 32 characters are not recommended.) Note that hyphens are not allowed. Name of IANA tunnelType requested: A short description (e.g., a protocol name), suitable to appear in a comment in the registry. Description of the proposed use of the IANA tunnelType: Requesters MUST include answers, either directly or via a link to some document with the answers, to the following questions in the explanation of the proposed use of the IANA tunnelType: o How would IP run over your tunnelType? o Would there be another interface sublayer between your tunnelType and IP? o Would your tunnelType be vendor-specific or proprietary? (If so, the label MUST start with a string that shows that. For example, if your company's name or acronym is xxx, then the tunnelType label would be something like xxxSomeTunnelTypeLabel.) o Would your tunnelType require or allow vendor-specific extensions? If so, would the vendor use their own tunnelType in a sub-layer below the requested tunnelType, or some sort of sub-type of the tunnelType, or some other mechanism? Reference, Internet-Draft, or Specification: A link to some document is required. Additional information or comments: Optionally any additional comments for IANA or the Designated Expert. 7. IANA Considerations This entire document is about IANA considerations, but this section discusses actions to be taken by IANA. There are three registries affected: 1. ifType definitions [ifType-registry]: The registration process is updated in Section 6.1, and the template is updated in Section 6.3.1. 2. tunnelType definitions [tunnelType-registry]: The registration process is updated in Section 6.1, and the template is updated in Section 6.3.2. Thaler & Romascanu Expires July 19, 2020 [Page 10] Internet-Draft ifType Guidelines January 2020 3. transmission numbers [transmission-registry]: The assignment process is updated in Section 6.2. 7.1. MIB and YANG Modules The following actions are to be taken to clarify the relationship between MIB modules, YANG modules, and the relevant registries: 1. Add the following note to the entry for the IANAifType-MIB at [protocol-registries]: "This is one of the available formats of the ifType and tunnelType registries." 2. Change the note on the entry for the iana-if-type YANG module at [protocol-registries] to read: "This is one of the available formats of the ifType registry." 3. Change the note on the entry for the iana-tunnel-type YANG module at [protocol-registries] to read: "This is one of the available formats of the tunnelType registry." 4. Create a section for "Interface Parameters" at [protocol-registries], with entries for "Interface Types (ifType)" [ifType-registry], "Tunnel Types (tunnelType)" [tunnelType-registry], and "Transmission Values" [transmission-registry]. 5. Update the ifType definitions registry [ifType-registry] to list MIB [IANAifType-MIB] and YANG [yang-if-type] as Available Formats. 6. Update the tunnelType definitions registry [tunnelType-registry] to list MIB [IANAifType-MIB] and YANG [yang-tunnel-type] as Available Formats, and change the title to "tunnelType Definitions" for consistency with the [ifType-registry] title. 7. Replace the [yang-if-type] page with the YANG module content, rather than having a page that itself claims to have multiple Available Formats. 8. Replace the [yang-tunnel-type] page with the YANG module content, rather than having a page that itself claims to have multiple Available Formats. In addition [IANAifType-MIB] is to be updated as follows: OLD: Requests for new values should be made to IANA via email (iana@iana.org). Thaler & Romascanu Expires July 19, 2020 [Page 11] Internet-Draft ifType Guidelines January 2020 NEW: Interface types must not be directly added to the IANAifType-MIB MIB module. They must instead be added to the "ifType definitions" registry at [ifType-registry]. (Note that [yang-if-type] was previously updated with this language.) 7.2. Transmission Number Assignments Per the discussion in Section 6.2, [ifType-registry] is to be updated as follows: OLD: For every ifType registration, the corresponding transmission number value should be registered or marked "Reserved." NEW: For future ifType assignments, an OID-subtree assignment MIB- II's 'transmission' subtree will be made with the same value. Similarly, the following change is to be made to [transmission-registry]: OLD: For every transmission number registration, the corresponding ifType value should be registered or marked "Reserved." NEW: For future transmission number assignments, an 'ifType' will be made with the same value. 8. Security Considerations Since this document does not introduce any technology or protocol, there are no security issues to be considered for this document itself. For security considerations related to MIB and YANG modules that expose these values, see Section 9 of [RFC2863], Section 6 of [RFC4087], and Section 3 of [I-D.ietf-softwire-iftunnel]. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc- editor.org/info/rfc2119>. Thaler & Romascanu Expires July 19, 2020 [Page 12] Internet-Draft ifType Guidelines January 2020 [RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J. Schoenwaelder, Ed., "Structure of Management Information Version 2 (SMIv2)", STD 58, RFC 2578, DOI 10.17487/RFC2578, April 1999, <https://www.rfc- editor.org/info/rfc2578>. [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, <https://www.rfc-editor.org/info/rfc2863>. [RFC5378] Bradner, S., Ed. and J. Contreras, Ed., "Rights Contributors Provide to the IETF Trust", BCP 78, RFC 5378, DOI 10.17487/RFC5378, November 2008, <https://www.rfc- editor.org/info/rfc5378>. [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. 9.2. Informative References [I-D.ietf-softwire-iftunnel] Boucadair, M., Farrer, I., and R. Asati, "Tunnel Interface Types YANG Module", draft-ietf-softwire-iftunnel-07 (work in progress), June 2019. [IANAifType-MIB] IANA, "IANAifType-MIB", February 2019, <http://www.iana.org/assignments/ianaiftype-mib>. [ifType-registry] IANA, "ifType definitions", June 2019, <https://www.iana.org/assignments/smi-numbers/smi- numbers.xhtml#smi-numbers-5>. [protocol-registries] IANA, "Protocol Registries", June 2019, <https://www.iana.org/protocols>. [RFC1234] Provan, D., "Tunneling IPX traffic through IP networks", RFC 1234, DOI 10.17487/RFC1234, June 1991, <https://www.rfc-editor.org/info/rfc1234>. Thaler & Romascanu Expires July 19, 2020 [Page 13] Internet-Draft ifType Guidelines January 2020 [RFC1573] McCloghrie, K. and F. Kastenholz, "Evolution of the Interfaces Group of MIB-II", RFC 1573, DOI 10.17487/RFC1573, January 1994, <https://www.rfc- editor.org/info/rfc1573>. [RFC2667] Thaler, D., "IP Tunnel MIB", RFC 2667, DOI 10.17487/RFC2667, August 1999, <https://www.rfc- editor.org/info/rfc2667>. [RFC3635] Flick, J., "Definitions of Managed Objects for the Ethernet-like Interface Types", RFC 3635, DOI 10.17487/RFC3635, September 2003, <https://www.rfc- editor.org/info/rfc3635>. [RFC3637] Heard, C., Ed., "Definitions of Managed Objects for the Ethernet WAN Interface Sublayer", RFC 3637, DOI 10.17487/RFC3637, September 2003, <https://www.rfc- editor.org/info/rfc3637>. [RFC4087] Thaler, D., "IP Tunnel MIB", RFC 4087, DOI 10.17487/RFC4087, June 2005, <https://www.rfc- editor.org/info/rfc4087>. [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through Network Address Translations (NATs)", RFC 4380, DOI 10.17487/RFC4380, February 2006, <https://www.rfc- editor.org/info/rfc4380>. [RFC5066] Beili, E., "Ethernet in the First Mile Copper (EFMCu) Interfaces MIB", RFC 5066, DOI 10.17487/RFC5066, November 2007, <https://www.rfc-editor.org/info/rfc5066>. [RFC7224] Bjorklund, M., "IANA Interface Type YANG Module", RFC 7224, DOI 10.17487/RFC7224, May 2014, <https://www.rfc-editor.org/info/rfc7224>. [transmission-registry] IANA, "transmission definitions", June 2019, <https://www.iana.org/assignments/smi-numbers/smi- numbers.xhtml#smi-numbers-7>. [tunnelType-registry] IANA, "Internet-standard MIB - mib- 2.interface.ifTable.ifEntry.ifType.tunnelType", June 2019, <https://www.iana.org/assignments/smi-numbers/smi- numbers.xhtml#smi-numbers-6>. Thaler & Romascanu Expires July 19, 2020 [Page 14] Internet-Draft ifType Guidelines January 2020 [yang-if-type] IANA, "iana-if-type YANG Module", February 2019, <http://www.iana.org/assignments/iana-if-type>. [yang-tunnel-type] IANA, "iana-tunnel-type YANG Module", June 2019, <https://www.iana.org/assignments/iana-tunnel-type>. Authors' Addresses Dave Thaler Microsoft EMail: dthaler@microsoft.com Dan Romascanu Independent EMail: dromasca@gmail.com Thaler & Romascanu Expires July 19, 2020 [Page 15]