Hi Les, I am proposing to include the text I sent along with your text.
You basically want to imply that when there is an ASLA advertised with an application bit set That application MUST use all link attributes that can appear in ASLA from only ASLAs having the specific application bit set and MUST NOT use from zero ABM ASLAs. I agree it is possible to Derive this from your latest text but I would prefer re-iterating this fact more directly than Let the readers derive this information from current text. Link attributes MAY be advertised associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications. Such advertisements MUST be used by standard applications and/or user defined applications when no link attribute advertisements with a non-zero-length Application Identifier Bit Mask and a matching Application Identifier Bit set are present for a given link. Otherwise, such advertisements MUST NOT be used. In other words, When an application specific link Attribute sub-TLV is advertised for a link with one or more specific standard application or user defined application bits set, all link attributes that are allowed in ASLA MUST be used from the ASLA sub-TLVs having that specific application bit set for that link. For the purposes of such applications, link attributes MUST NOT be used from ASLA sub-TLV with zero SABM & UDABM length. Rgds Shraddha Juniper Business Use Only From: Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org> Sent: Wednesday, June 16, 2021 10:26 PM To: Shraddha Hegde <shrad...@juniper.net>; Les Ginsberg (ginsberg) <ginsb...@cisco.com>; lsr@ietf.org Cc: DECRAENE Bruno IMT/OLN <bruno.decra...@orange.com>; Van De Velde, Gunter (Nokia - BE/Antwerp) <gunter.van_de_ve...@nokia.com> Subject: RE: Proposed Errata for RFCs 8919/8920 [External Email. Be cautious of content] Shraddha - I believe we are in agreement on when zero length ABM ASLA sub-TLVs can be used and when they cannot. The new text we proposed is: "Link attributes MAY be advertised associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications. Such advertisements MUST be used by standard applications and/or user defined applications when no link attribute advertisements with a non-zero-length Application Identifier Bit Mask and a matching Application Identifier Bit set are present for a given link. Otherwise, such advertisements MUST NOT be used." This states both when zero-length ABM advertisements MUST be used and when they MUST NOT be used. You have proposed different text: "When an application specific link Attribute sub-TLV is advertised with one or more specific standard application or user defined application bits set, all link attributes that are allowed in ASLA MUST be used from the ASLA sub-TLVs having that specific application bit set. For the purposes of such applications, link attributes MUST NOT be used from ASLA sub-TLV with zero SABM & UDABM length." This states when zero-length ABM advertisements MUST NOT be used - but it does not state when they MUST be used. Instead, it states when non-zero length ABM advertisements MUST be used. So this does not seem to be as complete as regards zero length ABM. You seem to feel that there is confusion as to when non-zero ABM ASLA advertisements MUST be used - but I do not understand why that is the case. You mention Maximum-Link-Bandwidth - for which there is a dedicated Section (4.2.1). The need for that section arises in order to make clear that different values for maximum-link-bandwidth are nonsensical and if they occur they all should be ignored. But Section 4.2.1 also references Sections 4.2 and 6.2 to make clear that the same constraints regarding the use of zero length ABM advertisements apply to maximum-link-bandwidth. So, I am not clear on what text is currently confusing, nor do I understand how your proposed text clarifies this confusion. I am open to revising the proposed text - but I need more help from you to understand the source of confusion. Les From: Lsr <lsr-boun...@ietf.org<mailto:lsr-boun...@ietf.org>> On Behalf Of Shraddha Hegde Sent: Wednesday, June 16, 2021 7:46 AM To: Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org<mailto:ginsberg=40cisco....@dmarc.ietf.org>>; lsr@ietf.org<mailto:lsr@ietf.org> Cc: DECRAENE Bruno IMT/OLN <bruno.decra...@orange.com<mailto:bruno.decra...@orange.com>>; Van De Velde, Gunter (Nokia - BE/Antwerp) <gunter.van_de_ve...@nokia.com<mailto:gunter.van_de_ve...@nokia.com>> Subject: Re: [Lsr] Proposed Errata for RFCs 8919/8920 Hi, I think that there may still be some ambiguity arising from the text below due to the fact that There are attributes such as maximum-link-bandwidth which have special behaviour mentioned in later sections. "Link attributes MAY be advertised associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications. Such advertisements MUST be used by standard applications and/or user defined applications when no link attribute advertisements with a non-zero-length Application Identifier Bit Mask and a matching Application Identifier Bit set are present for a given link. Otherwise, such advertisements MUST NOT be used." For example, If max link bandwidth attribute comes in a Zero length SABM & UDABM and we have a Flex-algo specific ASLA that does not have the max-link-bandwidth advertised, can Flex-algo use max-link-bandwidth attribute? My interpretation from modified text for ISIS is that, it cannot use it. I think there is no harm in re-iterating in order to avoid people reading is differently. Link attributes MAY be advertised associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications. Such advertisements MUST be used by standard applications and/or user defined applications when no link attribute advertisements with a non-zero-length Application Identifier Bit Mask and a matching Application Identifier Bit set are present for a given link. Otherwise, such advertisements MUST NOT be used. In other words, When an application specific link Attribute sub-TLV is advertised with one or more specific standard application or user defined application bits set, all link attributes that are allowed in ASLA MUST be used from the ASLA sub-TLVs having that specific application bit set. For the purposes of such applications, link attributes MUST NOT be used from ASLA sub-TLV with zero SABM & UDABM length. Rgds Shraddha Juniper Business Use Only From: Lsr <lsr-boun...@ietf.org<mailto:lsr-boun...@ietf.org>> On Behalf Of Les Ginsberg (ginsberg) Sent: Tuesday, June 15, 2021 8:55 PM To: lsr@ietf.org<mailto:lsr@ietf.org> Cc: DECRAENE Bruno IMT/OLN <bruno.decra...@orange.com<mailto:bruno.decra...@orange.com>>; Van De Velde, Gunter (Nokia - BE/Antwerp) <gunter.van_de_ve...@nokia.com<mailto:gunter.van_de_ve...@nokia.com>> Subject: [Lsr] Proposed Errata for RFCs 8919/8920 [External Email. Be cautious of content] Folks - Recent discussions on the list have highlighted some unintentional ambiguity in how ASLA advertisements are to be used. Please see https://mailarchive.ietf.org/arch/msg/lsr/prSLJDkMUnHm6h7VuCdn_Q7-1vg/<https://urldefense.com/v3/__https:/mailarchive.ietf.org/arch/msg/lsr/prSLJDkMUnHm6h7VuCdn_Q7-1vg/__;!!NEt6yMaO-gk!RK_eZNNu1y0aJvAqIaNwHTIFAjHWFJwW1UqyOO8ACxB0kof3jmD_dRkiPkbVLJyA$> The following proposed Errata address this ambiguity and aligns language in the two RFCs. We welcome comments on the proposed Errata before officially filing them. Les and Peter Errata Explanation Both RFC 8919 and RFC 8920 define advertising link attributes with zero length Standard Application Bit Mask (SABM) and zero length User Defined Application Bit Mask (UDABM) as a means of advertising link attributes that can be used by any application. However, the text uses the word "permitted", suggesting that the use of such advertisements is "optional". Such an interpretation could lead to interoperability issues and is not what was intended. The replacement text below makes explicit the specific conditions when such advertisements MUST be used and the specific conditions under which they MUST NOT be used. RFC 8919 Section 4.2: OLD "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 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 that is associated with a non-zero-length Application Identifier Bit Mask with a matching Application Identifier Bit set." NEW "Link attributes MAY be advertised associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications. Such advertisements MUST be used by standard applications and/or user defined applications when no link attribute advertisements with a non-zero-length Application Identifier Bit Mask and a matching Application Identifier Bit set are present for a given link. Otherwise, such advertisements MUST NOT be used." RFC 8919 Section 6.2 OLD "Link attribute advertisements associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications are usable by any application, subject to the restrictions specified in Section 4.2. If support for a new application is introduced on any node in a network in the presence of such advertisements, these advertisements are permitted to be used by the new application. If this is not what is intended, then existing advertisements MUST be readvertised with an explicit set of applications specified before a new application is introduced." NEW "Link attribute advertisements associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications are usable by any application, subject to the restrictions specified in Section 4.2. If support for a new application is introduced on any node in a network in the presence of such advertisements, the new application will use these advertisements, when the aforementioned restrictions are met. If this is not what is intended, then existing advertisements MUST be readvertised with an explicit set of applications specified before a new application is introduced." RFC 8920 Section 5 OLD "If link attributes are advertised with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications, then any standard application and/or any user-defined application is permitted to use that set of link attributes. If support for a new application is introduced on any node in a network in the presence of such advertisements, these advertisements are permitted to be used by the new application. If this is not what is intended, then existing advertisements MUST be readvertised with an explicit set of applications specified before a new application is introduced. An application-specific advertisement (Application Identifier Bit Mask with a matching Application Identifier Bit set) for an attribute MUST always be preferred over the advertisement of the same attribute with the zero-length Application Identifier Bit Masks for both standard applications and user-defined applications on the same link." NEW "Link attributes MAY be advertised associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications. Such advertisements MUST be used by standard applications and/or user defined applications when no link attribute advertisements with a non-zero-length Application Identifier Bit Mask and a matching Application Identifier Bit set are present for a given link. Otherwise, such advertisements MUST NOT be used." RFC 8920 New Section between 12.1 and 12.2. Current sections following this new section will need to be renumbered. 12.2 Use of Zero-Length Application Identifier Bit Masks "Link attribute advertisements associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications are usable by any application, subject to the restrictions specified in Section 5. If support for a new application is introduced on any node in a network in the presence of such advertisements, the new application will use these advertisements, when the aforementioned restrictions are met. If this is not what is intended, then existing advertisements MUST be readvertised with an explicit set of applications specified before a new application is introduced."
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