Benjamin Kaduk has entered the following ballot position for draft-ietf-isis-te-app-14: Discuss
When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel free to cut this introductory paragraph, however.) Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html for more information about IESG DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: https://datatracker.ietf.org/doc/draft-ietf-isis-te-app/ ---------------------------------------------------------------------- DISCUSS: ---------------------------------------------------------------------- My apologies if this is super-obvious and I'm just missing it ... but Section 4.3 dictates that part of the value for the application-specific SRLG TLV is a "Neighbor System-ID + pseudo-node ID (7 octets)". Where are these defined? (We don't exactly say that we're reusing the structure from, e.g., TLV 138, which I note refers to the seventh octet as "pseudonode number", not "pseudo-node ID". Similarly for the interpretation of the SRLG value(s). Do we just need to reference that we're reusing the encoding from RFC 5307 (or similar) or are some changes needed? ---------------------------------------------------------------------- COMMENT: ---------------------------------------------------------------------- What is the scope over which the user-defined application bits are defined/allocated? And, a general question, just to check my understanding: if I do need to specify different values of a given attribute for different applications, I do that by putting multiple copies of the new sub-TLV in TLV 22/23/etc., with the flags set according to which application the contained attributes apply to? (Mostly I ask because I forget what the rules are for having multiple instances of a given TLV/sub-TLV as siblings in the same container.) Section 3.1 Maybe mention (again, I know) that this is only the subset of sub-TLVs that are used for RSVP-TE? Section 4.2 When the L-flag is set in the Application Identifier Bit Mask, all of the applications specified in the bit mask MUST use the legacy advertisements for the corresponding link found in TLVs 22, 23, 25, 141, 222, and 223 or TLV 138 or TLV 139 as appropriate. Link nit(?): is this "found in sub-TLVs of TLVs 22, [...]"? attribute sub-sub-TLVs for the corresponding link attributes MUST NOT be advertised for the set of applications specified in the Standard/ User Application Identifier Bit Masks and all such advertisements MUST be ignored on receipt. Does this apply to just the (sub-)TLV with the L-flag set, or to other instances of that (sub-)TLV as well? For a given application, the setting of the L-flag MUST be the same in all sub-TLVs for a given link. In cases where this constraint is violated, the L-flag MUST be considered set for this application. editorial: I suggest "the L-flag MUST be considered set for this application for all sub-TLVs on the link in question". If link attributes are advertised associated with zero length Application Identifier Bit Masks for both standard applications and user defined applications, then any Standard Application and/or any Do we need to talk about conflicts if there are multiple such sub-TLVs for the link in question (that contain different values in the sub-sub-TLV(s))? User Defined Application is permitted to use that set of link attributes so long as there is not another set of attributes advertised on that same link which is associated with a non-zero length Application Identifier Bit Mask with a matching Application Identifier Bit set. nit: this phrasing of "matching Application Identifier Bit set" does not seem as clear as it could be that the bit for the application in question is what's checked (though I have a hard time believing that someone would accidentally misinterpret the meaning). the link attribute sub-sub-TLV code points. This document defines a sub-sub-TLV for each of the existing sub-TLVs listed in Section 3.1 except as noted below. The format of the sub-sub-TLVs matches the Just to check that I'm matching things up properly: this leaves the only attributes that do not have some form of exception noted as administrative group, extended administrative group, and TE default metric? Section 4.2.1 Maximum link bandwidth is an application independent attribute of the link. When advertised using the Application Specific Link Attributes sub-TLV, multiple values for the same link MUST NOT be advertised. This can be accomplished most efficiently by having a single advertisement for a given link where the Application Identifier Bit Mask identifies all the applications which are making use of the value for that link. If I want the same maximum link bandwidth to apply to all applications, couldn't I just put it in a sub-TLV with both SABM and UDABM length of zero? (Is this somehow less efficient than setting all the bits for the applications making use of the value?) Section 4.2.3 seems to discuss using the zero-length bit mask option in the context of TE metrics... (I do note the note at the end of Section 5 about the "any application" encoding leaving ambiguous whether an application is enabled, but I don't see how this consideration differs between maximum link bandwidth and extended TE metrics.) Section 4.2.2 Maximum Reservable Link Bandwidth and Unreserved Bandwidth are attributes specific to RSVP-TE. When advertised using the Application Specific Link Attributes sub-TLV, bits other than the RSVP-TE (R-bit) MUST NOT be set in the Application Identifier Bit Just to confirm: we find the risk of some future application that also wants to do reservation-like things sufficiently low that we're okay with preventing it from using these attributes? Section 4.3 What are the semantics when I specify more than one link identifier sub-TLV? They are all supposed to identify the same link, and in some case might be needed to disambiguate if there are (e.g.) multiple links to the same neighbor? Section 5 In the case of SRTE, advertisement of application specific link attributes does not indicate enablement of SRTE on that link. The Is the SRTE specification sufficiently final that we're comfortable enshrining in a (different) RFC this property of it? I note that we only list draft-ietf-spring-segment-routing-policy as an informative reference, so it's entirely possible that this document will be published as an RFC before that document is done. Section 6.1 the writing of this document. Therefore, such applications have been deployed using the legacy advertisements. The Standard Applications defined in this document may continue to use legacy advertisements for a given link so long as at least one of the following conditions is true: nit(?): do we want to say something like "may safely continue" or "may continue to use without ill effect"? Section 6.3.2 advertisements as defined in this document. Attributes for applications other than RSVP-TE MUST be advertised using application specific advertisements which have the L-flag clear. In cases where some link attributes are shared with RSVP-TE, this requires duplicate advertisements for those attributes. Maybe repeat that this duplication is required because the L flag applies per-application per-link, for all attributes? Section 6.3.4 2)Advertise all legacy link attributes using application specific advertisements with L-flag clear and R-bit set. nit: I suggest clarifying that this involves duplicate advertisements (legacy plus application-specific). Or at least, I assume it does, since step (3) is "remove legacy advertisements". Section 7.3 Note to IANA: For future codepoints, in cases where the document which defines the encoding is different from the document which assigns the codepoint, the encoding reference MUST be to the document which defines the encoding. Why not list both as the reference? Note to designated experts: If a link attribute can be advertised both as a sub-TLV of TLVs 22, 23, 25, 141, 222, and 223 and as a sub- sub-TLV of the Application Specific Link Attributes sub-TLV defined in this document, then the same numerical code should be assigned to the link attribute whenever possible. Are these notes intended to end up in the final RFC, attached to the registry, both places, or neither place? Section 7.4 policy for this registry is "Standards Action" [RFC8126]. Bit definitions SHOULD be assigned in ascending bit order beginning with Bit 0 so as to minimize the number of octets that will need to be transmitted. The following assignments are made by this document: I worry a little bit that this will encourage codepoint squatting, though in theory the user-defined bitmask should avoid the need for squatting. Section 7.5 Note to IANA: For future codepoints, in cases where the document which defines the encoding is different from the document which assigns the codepoint, the encoding reference MUST be to the document which defines the encoding. (As above, why not list both?) _______________________________________________ Lsr mailing list [email protected] https://www.ietf.org/mailman/listinfo/lsr
