Olivier, On 11/09/2020 16:18, olivier.dug...@orange.com wrote:
Hi all,Well, re-reading again the draft, I'm finally a bit confused about this thread around the metric. If I correctly summarise, the goal of this draft is to standardised flex algo, and consequently, new opcode allocated by IANA that are convey in IS-IS and OSPF. Looking to IANA section, let me think that the major point is to be agree on code point to specify algo and for SID, reference to a particular algo.
Felx-algo draft does not specify algorithm, algorithm is defined by the user. Nor does it define a algo specific SID, that has been defined in the existing RFCs.
So, IETF is standardized protocol, not architecture, nor algorithm. So, the way a router compute nexthop route for flex algo X is normally out of scope of the draft.
The role of IGPs is to compute paths and IGP base specifications clearly specify how a path is computed for default algorithm. Flex-algo draft specifies how Flex-algo path is computed in IGPs. This is absolutely critical, because if there is an inconsistency on how the path is computed between different nodes in the network permanent loops could be formed.
Thus, for delay or TE flex algo, an implementer would be free to pick delay or TE metric to compute the nexthop route. What must be standardized for interoperability purpose if the code point to convey flex algo value. Indeed, the metrics value used by the router are completely orthogonal from the flex algo code point and the algorithm that compute the route. For example, a flex algo could used legacy metric or new ALSA announce by the IGP itself or a static value configured locally or through a management system.In fact, I'm referring to PCE and PCEP protocol which more or less do the same thing i.e. compute a route based on topology and metrics. In any RFCs related to PCE you will find a mention about how PCE must acquire the topology and a specific metric. it is up to the implementer. This is the same for the various algorithm. Only objective functions are standardized and only code point to convey metrics in PCEP Request and Response are standardized.
there is a fundamental difference between PCE and IGPs. PCE is a centralized entity, which computes the path and enforces such path on the network. Indeed, it can compute the path the way it likes it, because it's only the PCE that does the computation for the path. IGPs are doing distributed computation and it is absolutely critical to make sure that all nodes compute the path the same way and use the same inputs.
So, I'm a bit surprised that this draft *impose* the origin of the metric for the flex algo route computation and not be more flexible letting the implementer free to select metrics from which it would.
it is not possible to let the choice for implementation, because if nodes from different implementations pick different values during the computation, in distributed calculation this will result in loops.
And don't argue that it is for interoperability (the draft will not define how to convey metric used by flex algo) nor to achieve a global coherent route as each router take a local decision to compute nexthop router which absolutely doesn't guarantee that the route follow by a packet from A to Z is the shortest from a TE metric or a delay metric.
I'm afraid your understanding of distributed path computation is wrong.IGP calculation does guarantee a coherent path selection over the network, it is a fundamental property of the IGP computed paths. And Flex-algo allows you to use different metrics to compute such paths.
Only a central path computation e.g. with a PCE could guarantee that.
obviously not. regards, Peter
Regards Olivier Le 03/09/2020 à 14:49, Van De Velde, Gunter (Nokia - BE/Antwerp) a écrit :I think that some misunderstanding comes from a different definition of " LEGACY ADVERTISEMENTS" between section 4.2 and 6.1 In section 4.2: LEGACY ADVERTISEMENTS means that *ASLA is used* and point to the attributes found in legacy TLVs for example EAG, Delay and TE-metric In section 6.1: LEGACY ADVERTISEMENTS means that *ASLA is NOT used* and allows RSVP-TE, SR-Policy and LFA to interoperate between systems that do not, and do, support ASLA Taking this understanding to flex-algo: * Interop: traditionally we use the L-bit=SET for application interoperability when not all nodes understand valid ASLA encoding. * Interop: by design of flex-algorithm technology, we mandate ASLA encoding. No interop issues should exist with nodes not understanding ASLA encodings. * Why would a flex-algo node, ever, advertise legacy TLVs for flex-algo attributes? There seems no use-case and no logic for such. * OSPF has no existing L-bit For flex-algo simplicity, we could agree that legacy attribute advertisements MUST NOT be used and agree that flex-algo ASLA L-bit MUST be UNSET (This is unrelated that flex-algo ASLA with L-bit SET is semantically a valid ASLA. This also simplifies and align ISIS and OSPF routing protocol behavior. It reduce interop issues footprint with systems not supporting ASLA.) G/ -----Original Message-----From: Peter Psenak<ppse...@cisco.com> Sent: Thursday, September 3, 2020 12:02To: Van De Velde, Gunter (Nokia - BE/Antwerp)<gunter.van_de_ve...@nokia.com>; Selderslaghs, Rudy (Nokia - BE/Antwerp)<rudy.seldersla...@nokia.com>; Shraddha Hegde<shrad...@juniper.net>;olivier.dug...@orange.com;tony...@tony.li; Robert Raszuk<rob...@raszuk.net> Cc: Christian Hopps<cho...@chopps.org>;draft-ietf-lsr-flex-algo....@ietf.org; Les Ginsberg (ginsberg)<ginsb...@cisco.com>;lsr@ietf.org;lsr-...@ietf.org; Acee Lindem (acee)<a...@cisco.com> Subject: Re: [Lsr] WG Last Call for draft-ietf-lsr-flex-algo Gunter, On 03/09/2020 11:53, Van De Velde, Gunter (Nokia - BE/Antwerp) wrote:Hi Peter, All, Let me chime in. When the L-bit is set in an ASLA TLV, then for all applications marked, indeed only legacy attributes can be used. Of course an ASLA TLV with the L-bit set is a valid ASLA advertisement. That is not the point. Read the text in chapter 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.This clearly says that when the L-bit is set, the LEGACY ADVERTISEMENTS have to be used. However chapter 6.1 is saying that legacy advertisements can only be used for RSVP-TE, SR-Policy and LFA.where? Please point me to the text. If you are referring to the text: "New applications that future documents define to make use of the advertisements defined in this document MUST NOT make use of legacy advertisements." then it is NOT preventing L-bit with legacy advertisement for new apps, because ASLA with L-bit in combination with legacy advertisement is not considered as legacy advertisement, but as a valid ASLA advertisement.So in my opinion the draft is saying the opposite and legacy advertisements MUST NOT be used for flex-algo.again, L-bit with legacy advertisement is NOT a legacy advertisement. It is ASLA advertisement.Hence, I suggest that we should make it explicit clear that L-bit set for flex-algo is MUST NOT be allowed.L-bit is allowed with any app, including the flex-algo. thanks, PeterG/ -----Original Message----- From: Lsr<lsr-boun...@ietf.org> On Behalf Of Peter Psenak Sent: Thursday, September 3, 2020 11:19 To: Selderslaghs, Rudy (Nokia - BE/Antwerp) <rudy.seldersla...@nokia.com>; Peter Psenak <ppsenak=40cisco....@dmarc.ietf.org>; Shraddha Hegde <shrad...@juniper.net>;olivier.dug...@orange.com;tony...@tony.li; Robert Raszuk<rob...@raszuk.net> Cc: Christian Hopps<cho...@chopps.org>; draft-ietf-lsr-flex-algo....@ietf.org; Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org>;lsr@ietf.org;lsr-...@ietf.org; Acee Lindem (acee)<a...@cisco.com> Subject: Re: [Lsr] WG Last Call for draft-ietf-lsr-flex-algo Hi Rudy, On 03/09/2020 11:01, Selderslaghs, Rudy (Nokia - BE/Antwerp) wrote:Hi Peter, My interpretation of the isis-te-app draft is that an ASLA TLV with L-bit set to 1, cannot be used for Flex-Algo.no, that is not correct.This can only be used for RSVP-TE, SR-Policy and LFA as specified in chapter 6.1.no.>From chapter 6.1 Use of Legacy advertisements: ... New applications that future documents define to make use of the advertisements defined in this document MUST NOT make use of legacy advertisements. This simplifies deployment of new applications by eliminating the need to support multiple ways to advertise attributes for the new applications.ASLA with L-bit pointing to legacy TLV is NOT considered legacy advertisement. It is valid ASLA advertisement.Chapter 4.2. states that ASLA TLV with L-bit set means "using legacy advertisements":no. It says that if L-flag is set, all apps mentioned in the bitmask MUST use the legacy advertisement to derive the value of the attribute. It does NOT say that ASLA TLV with L-bit set means "using legacy advertisements". It does not. thanks, Peter... 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. Regards, Rudy -----Original Message----- From: Lsr<lsr-boun...@ietf.org> On Behalf Of Peter Psenak Sent: Thursday, September 3, 2020 9:55 AM To: Shraddha Hegde<shrad...@juniper.net>;olivier.dug...@orange.com; tony...@tony.li; Robert Raszuk<rob...@raszuk.net> Cc: Christian Hopps<cho...@chopps.org>; draft-ietf-lsr-flex-algo....@ietf.org; Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org>;lsr@ietf.org; lsr-...@ietf.org; Acee Lindem (acee)<a...@cisco.com> Subject: Re: [Lsr] WG Last Call for draft-ietf-lsr-flex-algo Hi Shraddha, On 03/09/2020 05:39, Shraddha Hegde wrote:Peter, In order to make the document clearer on this point, I would like the text below to be added to section 11 to make it explicit that setting the L-bit is valid for flex-algo for ISIS. ============= Section 11. “The ASLA TLV in ISIS supports the L-Bit as described in section 4.2 of [draft-ietf-isis-te-app]. When the L-bit is set, applications MUST use legacy advertisements for that link. Flex algorithm application MUST support sending and receiving link attributes with ASLA TLV having L-bit set.I can add the above, although, it's clear from the draft-ietf-isis-te-app that L-bit with legacy advertisement MAY be used for any app.Note that earlier versions of this document did not mandate use of ASLA TLVs and hence may not inter-operate with early implementations that use legacy advertisements."it is not true that "earlier versions of this document" did not mandate ASLA. https://tools.ietf.org/html/draft-ietf-lsr-flex-algo-00, which only supported the include/exclude Admin Groups, clearly stated: 9. Advertisement of Link Attributes for Flex-Algorithm Various link include or exclude rules can be part of the Flex- Algorithm definition. These rules use Admin Groups (AG) as defined in [RFC7308] and [RFC5305], or Extended Administrative Groups (EAG) as defined in [RFC7308]. To advertise a link affinity in a form of the AG or EAG that is used during Flex-Algorithm calculation, an Application Specific Link Attributes sub-TLV as described in [I-D.ietf-isis-te-app], or sub-TLV of Extended Link TLV as described in [I-D.ietf-ospf-te-link-attr-reuse] MUST be used. The advertisement MUST indicate that it is usable by the Flex-Algorithm application. thanks, Peter============ Rgds Shraddha Juniper Business Use Only -----Original Message----- From: Peter Psenak<ppse...@cisco.com> Sent: Wednesday, September 2, 2020 2:43 PM To: Shraddha Hegde<shrad...@juniper.net>; olivier.dug...@orange.com;tony...@tony.li; Robert Raszuk <rob...@raszuk.net> Cc: Christian Hopps<cho...@chopps.org>; draft-ietf-lsr-flex-algo....@ietf.org; Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org>;lsr@ietf.org; lsr-...@ietf.org; Acee Lindem (acee)<a...@cisco.com> Subject: Re: [Lsr] WG Last Call for draft-ietf-lsr-flex-algo [External Email. Be cautious of content] Hi Shraddha, please see inline: On 02/09/2020 06:45, Shraddha Hegde wrote:Peter, It is worthwhile to note the history of the flex-algo draft and the te-app draft and how many backward incompatible changes have been introduced in the course of the flex-algo draft. The original drafts of flex-algo did not mention the te-app draft and was completely based on legacy advertisements. Two years ago, after the working group adopted the original drafts without the ASLA TLV, the text was changed to require the ASLA TLV.draft-ietf-lsr-flex-algo-00, which was the initial version of the WG document already mandated the ASLA usage. I don't believe we have to go back to the individual drafts that predated the WG version.ASLA TLV had the L-Bit and it was always valid to advertise link attributes for flex-algo with L-bit set which means the link attributes could still be sent in legacy TLVs. In a conversation last year, you had agreed that advertising link attributes with L-bit set is valid for Flex-algo.what we say in flex-algo draft in section 11 is: "Link attribute advertisements that are to be used during Flex- Algorithm calculation MUST use the Application-Specific Link Attribute (ASLA) advertisements defined in [I-D.ietf-isis-te-app] or [I-D.ietf-ospf-te-link-attr-reuse]." ietf-isis-te-app clearly allows the app specific value of the attribute to be advertised in legacy TLV and be pointed to by ASLA with L-bit. This is perfectly valid for Flex-algo with ISIS. Please note that etf-ospf-te-link-attr-reuse does not have the concept of L-bit.Towards the end of 2019, draft-ietf-isis-te-app-08 was posted. This version said that only RSVP, SR-TE and LFA can use legacy advertisements. This change in a different draft made using flex-algo with legacy advertisements invalid.no, not really. From the version 00, the WG version of the flex-algo draft mandated the usage of ASLA. And from day one of the draft-ietf-isis-te-app draft we mandated the usage of the ALSA for new applications, including the flex-algo. And usage of ASLA with L-bit together with the legacy advertisement of the link attribute is valid for any new application.So implementations from 2 yrs ago may not inter-operate with the ones implemented a year ago or the ones implemented based on published RFC.let's be more precise here. The implementation of the pre-WG version may not inter-operate with WG version. I don't see a problem there really.Implementations from a year ago may not interoperate with published RFC.no, that is not true.I don’t agree with this series of backward incompatible changes that have been made in this document. However, if the working group decides to go ahead and request publication of the current version, which has broken backward compatibility twice with previous versions,above statement is not correct. The WG document has been consistent in terms of ASLA usage from day one. thanks, PeterI want the history to be accurately recorded. This allows network operators to better understand the history and ensure interoperability across vendors before deploying. Rgds Shraddha Juniper Business Use Only -----Original Message----- From: Peter Psenak<ppse...@cisco.com> Sent: Thursday, August 27, 2020 3:34 PM To: Shraddha Hegde<shrad...@juniper.net>; olivier.dug...@orange.com;tony...@tony.li; Robert Raszuk <rob...@raszuk.net> Cc: Christian Hopps<cho...@chopps.org>; draft-ietf-lsr-flex-algo....@ietf.org; Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org>;lsr@ietf.org; lsr-...@ietf.org; Acee Lindem (acee)<a...@cisco.com> Subject: Re: [Lsr] WG Last Call for draft-ietf-lsr-flex-algo [External Email. Be cautious of content] Hi Shraddha, draft-ietf-lsr-flex-algo-00 was published May 15, 2018 (over two years ago). It clearly stated: https://urldefense.com/v3/__https://tools.ietf.org/html/draft-ietf- lsr -flex-algo-00*section-9__;Iw!!NEt6yMaO-gk!U69buL_O8Dwro3_ks7FCVPZ2- jnY KFPl7DWC_fZCGDapvakBVKlZPth_03Sd1J7b$ "To advertise a link affinity in a form of the AG or EAG that is used during Flex-Algorithm calculation, an Application Specific Link Attributes sub-TLV as described in [I-D.ietf-isis-te-app], or sub-TLV of Extended Link TLV as described in [I-D.ietf-ospf-te-link-attr-reuse] MUST be used. The advertisement MUST indicate that it is usable by the Flex-Algorithm application." This is consistent with normative statements in both https://urldefense.com/v3/__https://tools.ietf.org/html/draft-ietf- isi s-te-app-19__;!!NEt6yMaO-gk!U69buL_O8Dwro3_ks7FCVPZ2-jnYKFPl7DWC_fZ CGD apvakBVKlZPth_09_HTtuT$ and https://urldefense.com/v3/__https://datatracker.ietf.org/doc/draft- iet f-ospf-te-link-attr-reuse/__;!!NEt6yMaO-gk!U69buL_O8Dwro3_ks7FCVPZ2 -jn YKFPl7DWC_fZCGDapvakBVKlZPth_08_P1Wmy$ which REQUIRE the use of application specific advertisements by all applications other than the legacy applications (RSVP-TE, Segment Routing Policy, Loop Free Alternate). draft-hegdeppsenak-isis-sr-flex-algo had a lifetime of 10 months(V00 published in July 2017) and draft-ppsenak-ospf-sr-flex-algo only 3 months (V00 published in Feb 2018). Juniper may have its own reasons why over the course of the past two years it has chosen not to modify its early implementation to be compatible with what is defined in the WG adopted draft. We do not question this choice. But it seems the most appropriate way to communicate this is for Juniper to document in its vendor specific documents that its implementation is based on a pre-WG draft and is incompatible with the IETF defined standard. IETF documents are not the correct place for such proprietary information. It is obvious that the implementation that is not following the final specification will not interoperate with other implementations that do so. There is no need to mention that in the RFC. thanks, Peter and Les On 25/08/2020 17:27, Shraddha Hegde wrote:Hi All, draft-lsr-flex-algo-00 was created by combining draft-hegdeppsenak-isis-sr-flex-algo-02 and draft-ppsenak-ospf-sr-flex-algo-00. When draft-lsr-flex-algo-00 was published as a WG document, it included a requirement for using te-app encodings that did not exist in either draft-hegdeppsenak-isis-sr-flex-algo-02 and draft-ppsenak-ospf-sr-flex-algo-00. Juniper's currently released implementation of flex-algo uses legacy encodings, as opposed to te-app encodings. I would like the following text added to draft-lsr-flex-algo in order to record the history of these changes and to make operators aware of possible inter-op problems that may arise due to the non-backward compatible nature of mandating ASLA encodings. ===== 11. Advertisement of Link Attributes for Flex-Algorithm " Earlier versions of this draft did not mandate the use of ASLA TLVs for encoding the link attributes. There may be implementations that depend on legacy encodings as defined in RFC 5305, RFC 7810 , RC 3630 and RFC 7471. Implementations that look at only ASLA encodings for flex-algo based on this version of the document will not interoperate with versions that use legacy advertisements. " ======== Rgds Shraddha Juniper Business Use Only *From:*olivier.dug...@orange.com<olivier.dug...@orange.com> *Sent:* Thursday, August 20, 2020 7:56 PM *To:* Peter Psenak<ppse...@cisco.com>;tony...@tony.li; Robert Raszuk<rob...@raszuk.net> *Cc:* Christian Hopps<cho...@chopps.org>; draft-ietf-lsr-flex-algo....@ietf.org; Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org>;lsr@ietf.org; lsr-...@ietf.org; Acee Lindem (acee)<a...@cisco.com> *Subject:* Re: [Lsr] WG Last Call for draft-ietf-lsr-flex-algo *[External Email. Be cautious of content]* Peter, Le 20/08/2020 à 14:12, Peter Psenak a écrit : Hi Olivier, On 20/08/2020 13:58,olivier.dug...@orange.com <mailto:olivier.dug...@orange.com> wrote: Hi Peter, Thank for the new version. Le 19/08/2020 à 14:00, Peter Psenak a écrit : Olivier, [ ... ] So, to speed up the deployment, I would prefer a reference to a delay value that could be advertise by means of RFC7471, RFC8570 and/or TE-App draft. It is then up to the operator to ensure the coherency of what it is announced in its network by the different routers. I know you don't like the app specific link advertisement, but I'm afraid what you ask for is absolutely wrong. We defined the ASLA encoding to address a real problems for advertising the link attributes. We allow the link attributes to be advertised in both legacy and ASLA advertisement for legacy application (RSVP-TE, SRTE) to address the backward compatibility. Flex-algo is a new application, there is absolutely no need to use the legacy advertisement. Doing so would just extend the problem to the flex-algo application. Regarding the new version you provided, new section 5.1 (for IS-IS) and section 5.2 (for OSPF) mention respectively RFC 8570 and RFC 7471 for the definition of Min delay and TE metric which is fine for me. But, they also made reference to draft isis-te-app, respectively ospf-te-link-attr-reuse to encode these value. that's what people were asking for. And it is right because we are mandating the usage of ALSA encoding for any flex-algo related link attributes. Here, it is confusing. I don't see how much more clear we can make it. Indeed, RFC 8570 and RFC 7471 also define the way to encode TE metric and Min delay. you have to distinguish between two things: a) where Min delay and TE metric were defined - RFC 8570 and RFC 7471 b) how we encode it for flex-algo - isis-te-app, ospf-te-link-attr-reuse What I'm suggesting, is a clear reference to the RFC for TE metric and Min delay definition as well as the encoding (especially for the delay) while leaving open the door to how the router acquire these values: legacy a.k.a. RFC 8570 & 7471 or new draft a.k.a draft-isis-te-app & draft-ospf-link-attr-reuse. no. This will not be done. We only allow ASLA advertisement for these metrics and other link attributes that are used for flex-algo. It is done for a reason and I have already explained that. OK. Reading section 11 which clarify how metrics are convey, let me suggest to make a reference to section 11 in section 5.1 and 5.2 instead of reference to drafts. In fact, in section 17.1.2, you mention only reference to RFC 8570 & RFC7471 for the IANA definition which is fine for me. because in registry, we are defining a metric type, not how we are going to advertise it for the link. OK. I would suggest the same wording for section 5.1. and 5.2 leaving operator free about how it collect the values from the neighbour routers: legacy or new method. please stop trying to make use of legacy RSVP-TE link advertisements for flex-algo - it will not be allowed. This raise to me a simple question: Is it possible to use 2 different Flex Algo with delay metric, one for App A and another one for App B ? if yes, how can we link metrics advertise in ALSA A from metrics advertise in ALSA B ? The draft mention only one bit for Flex-Algo. Regards, Olivier PS. I note a duplicate paragraph in section 12: "When computing the path for a given Flex-Algorithm, the metric-type that is part of the Flex-Algorithm definition (Section 5) MUST be used." thanks, Peter Regards Olivier PS. We have a pre-alpha implementation of flex algo using the legacy metrics and I know that recent IOS-XR provided similar implementation of flex algo based on legacy metrics. regards, Peter Regards Olivier Le 18/08/2020 à 19:02,tony...@tony.li <mailto:tony...@tony.li> a écrit : Robert, Thank you, exactly. We just need a clarification of the document. I don’t understand why this is such a big deal. Tony On Aug 18, 2020, at 9:22 AM, Robert Raszuk <rob...@raszuk.net <mailto:rob...@raszuk.net> <mailto:rob...@raszuk.net> <mailto:rob...@raszuk.net>> wrote: Les, I think this is not very obvious as Tony is pointing out. See RFC 8570 says: Type Description ---------------------------------------------------- 33 Unidirectional Link Delay 34 Min/Max Unidirectional Link Delay That means that is someone implementing it reads text in this draft literally (meaning Minimum value of Unidirectional Link Delay) it may pick minimum value from ULD type 33 :) If you want to be precise this draft may say minimum value of Min/Max Unidirectional Link Delay (34) and be done. That's all. Cheers, R. On Tue, Aug 18, 2020 at 6:04 PM Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org <mailto:ginsberg=40cisco....@dmarc.ietf.org> <mailto:40cisco....@dmarc.ietf.org> <mailto:40cisco....@dmarc.ietf.org>> wrote: Tony – As an author of both RFC 8570 and I-D.ietf-isis-te-app, I am not sure why you are confused – nor why you got misdirected to code point 33. RFC 8570 (and its predecessor RFC 7810) define: 34 Min/Max Unidirectional Link Delay This sub-TLV contains two values: “Min Delay: This 24-bit field carries the minimum measured link delay value (in microseconds) over a configurable interval, encoded as an integer value. Max Delay: This 24-bit field carries the maximum measured link delay value (in microseconds) over a configurable interval, encoded as an integer value.” It seems clear to me that the flex-draft is referring to Min Unidirectional Link Delay in codepoint 34. I agree it is important to be unambiguous in specifications, but I think Peter has been very clear. Please explain how you managed to end up at code point 33?? Les *From:* Lsr <lsr-boun...@ietf.org <mailto:lsr-boun...@ietf.org> <mailto:lsr-boun...@ietf.org> <mailto:lsr-boun...@ietf.org>> *On Behalf Of *tony...@tony.li <mailto:*tony...@tony.li> <mailto:tony...@tony.li> <mailto:tony...@tony.li> *Sent:* Tuesday, August 18, 2020 7:44 AM *To:* Peter Psenak (ppsenak) <ppse...@cisco.com <mailto:ppse...@cisco.com> <mailto:ppse...@cisco.com> <mailto:ppse...@cisco.com>> *Cc:*lsr@ietf.org <mailto:lsr@ietf.org> <mailto:lsr@ietf.org> <mailto:lsr@ietf.org>; lsr-...@ietf.org <mailto:lsr-...@ietf.org> <mailto:lsr-...@ietf.org> <mailto:lsr-...@ietf.org>; Christian Hopps <cho...@chopps.org <mailto:cho...@chopps.org> <mailto:cho...@chopps.org> <mailto:cho...@chopps.org>>; Acee Lindem (acee) <a...@cisco.com <mailto:a...@cisco.com> <mailto:a...@cisco.com> <mailto:a...@cisco.com>>; draft-ietf-lsr-flex-algo....@ietf.org <mailto:draft-ietf-lsr-flex-algo....@ietf.org> <mailto:draft-ietf-lsr-flex-algo....@ietf.org> <mailto:draft-ietf-lsr-flex-algo....@ietf.org> *Subject:* Re: [Lsr] WG Last Call for draft-ietf-lsr-flex-algo Hi Peter, section 5.1 of the draft-ietf-lsr-flex-algo says: Min Unidirectional Link Delay as defined in [I-D.ietf-isis-te-app]. We explicitly say "Min Unidirectional Link Delay", so this cannot be mixed with other delay values (max, average). The problem is that that does not exactly match “Unidirectional Link Delay” or “Min/Max Unidirectional Link Delay”, leading to the ambiguity. Without a clear match, you leave things open to people guessing. Now, it’s a metriic, so of course, you always want to take the min. So type 33 seems like a better match. section 7.3. of ietf-isis-te-app says: Type Description Encoding Reference --------------------------------------------------------- 34 Min/Max Unidirectional Link Delay RFC8570 And it also says: 33 Unidirectional Link Delay RFC8570<https://urldefense.com/v3/__https://tools.ietf.org/html/rfc8570__;!! NEt6yMaO-gk!U69buL_O8Dwro3_ks7FCVPZ2-jnYKFPl7DWC_fZCGDapvakBVKlZPt h_0 3pN2Sfl$ ><https://urldefense.com/v3/__https:/tools.ietf.org/html/rfc8570__; !!N E t6yMaO-gk!WKuLWanfqtEwcGfdMcPi6zO93gLNz6GLtiLn6c7mmIPhPYuTAufXgyh1 ir2 Q Dxsg$>This does not help. So, IMHO what we have now is correct and sufficient, but I have no issue adding the text you proposed below. What you have now is ambiguous. We have a responsibility, as writers of specifications, to be precise and clear. We are not there yet. BTW, before I posted 09 version of flex-algo draft, I asked if you were fine with just referencing ietf-isis-te-app in 5.1. I thought you were, as you did not indicate otherwise. My bad, I should have pressed the issue. Anyway, I consider this as a pure editorial issue and hopefully not something that would cause you to object the WG LC of the flex-algo draft. I’m sorry, I think that this is trivially resolved, but important clarification. You also have an author’s email that is bouncing, so at least one more spin is required. 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