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]>; draft-ietf-lsr-flex-
[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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