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.

So in my opinion the draft is saying the opposite and legacy advertisements 
MUST NOT be used for flex-algo.
Hence, I suggest that we should make it explicit clear that L-bit set for 
flex-algo is MUST NOT be allowed.

G/




-----Original Message-----
From: Lsr <[email protected]> On Behalf Of Peter Psenak
Sent: Thursday, September 3, 2020 11:19
To: Selderslaghs, Rudy (Nokia - BE/Antwerp) <[email protected]>; 
Peter Psenak <[email protected]>; Shraddha Hegde 
<[email protected]>; [email protected]; [email protected]; Robert 
Raszuk <[email protected]>
Cc: Christian Hopps <[email protected]>; [email protected]; 
Les Ginsberg (ginsberg) <[email protected]>; [email protected]; 
[email protected]; Acee Lindem (acee) <[email protected]>
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 <[email protected]> On Behalf Of Peter Psenak
> Sent: Thursday, September 3, 2020 9:55 AM
> To: Shraddha Hegde <[email protected]>; [email protected]; 
> [email protected]; Robert Raszuk <[email protected]>
> Cc: Christian Hopps <[email protected]>; 
> [email protected]; Les Ginsberg (ginsberg) 
> <[email protected]>; [email protected]; [email protected]; Acee 
> Lindem (acee) <[email protected]>
> 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 <[email protected]>
>> Sent: Wednesday, September 2, 2020 2:43 PM
>> To: Shraddha Hegde <[email protected]>; [email protected]; 
>> [email protected]; Robert Raszuk <[email protected]>
>> Cc: Christian Hopps <[email protected]>; 
>> [email protected]; Les Ginsberg (ginsberg) 
>> <[email protected]>; [email protected]; [email protected]; Acee 
>> Lindem (acee) <[email protected]>
>> 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,
>> Peter
>>
>>
>>>     I 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 <[email protected]>
>>> Sent: Thursday, August 27, 2020 3:34 PM
>>> To: Shraddha Hegde <[email protected]>; [email protected];
>>> [email protected]; Robert Raszuk <[email protected]>
>>> Cc: Christian Hopps <[email protected]>;
>>> [email protected]; Les Ginsberg (ginsberg)
>>> <[email protected]>; [email protected]; [email protected];
>>> Acee Lindem (acee) <[email protected]>
>>> 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_fZCGD
>>> 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:*[email protected] <[email protected]>
>>>> *Sent:* Thursday, August 20, 2020 7:56 PM
>>>> *To:* Peter Psenak <[email protected]>; [email protected]; Robert
>>>> Raszuk <[email protected]>
>>>> *Cc:* Christian Hopps <[email protected]>;
>>>> [email protected]; Les Ginsberg (ginsberg)
>>>> <[email protected]>; [email protected];
>>>> [email protected]; Acee Lindem (acee) <[email protected]>
>>>> *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, [email protected]
>>>>        <mailto:[email protected]> 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, [email protected]
>>>>                    <mailto:[email protected]> 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
>>>>                            <[email protected] <mailto:[email protected]>
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>> 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) <[email protected]
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>> 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 <[email protected]
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>>
>>>>                                 *On Behalf Of *[email protected]
>>>>                            <mailto:*[email protected]>
>>>>                            <mailto:[email protected]> 
>>>> <mailto:[email protected]>
>>>>                                 *Sent:* Tuesday, August 18, 2020 7:44 AM
>>>>                                 *To:* Peter Psenak (ppsenak)
>>>>                            <[email protected] <mailto:[email protected]>
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>>
>>>>                                 *Cc:* [email protected] <mailto:[email protected]>
>>>>                            <mailto:[email protected]> <mailto:[email protected]>;
>>>>                            [email protected] <mailto:[email protected]>
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>; Christian Hopps
>>>>                            <[email protected] <mailto:[email protected]>
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>>; Acee Lindem (acee)
>>>>                            <[email protected] <mailto:[email protected]>
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>>;
>>>>                            [email protected]
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>
>>>>                            <mailto:[email protected]>
>>>>                                 *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_fZCGDapvakBVKlZPth_0
>>>> 3pN2Sfl$ >
>>>>
>>>> <https://urldefense.com/v3/__https:/tools.ietf.org/html/rfc8570__;!!N
>>>> E
>>>> t6yMaO-gk!WKuLWanfqtEwcGfdMcPi6zO93gLNz6GLtiLn6c7mmIPhPYuTAufXgyh1ir2
>>>> 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.
>>>>
>>>>                                 Sorry,
>>>>
>>>>                                 Tony
>>>>
>>>>
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>>>> y
>>>> h1ivswJmIk$>
>>>>
>>>>
>>>>
>>>>
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>>>>
>>>>
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>>
>>
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