*
The first point can be addressed as a note to the RFC Editor. Having a
note in the registry would make sense for the second point.
Cheers,
Med
*De :*Peter Psenak <[email protected]>
*Envoyé :* vendredi 1 août 2025 11:47
*À :* BOUCADAIR Mohamed INNOV/NET <[email protected]>; The
IESG <[email protected]>
*Cc :* [email protected];
[email protected]; [email protected]; [email protected]
*Objet :* Re: Mohamed Boucadair's Discuss on
draft-ietf-lsr-igp-flex-algo-reverse-affinity-07: (with DISCUSS and
COMMENT)
Hi Med,
please see inline (##PP):
On 01/08/2025 10:48, [email protected] wrote:
Hi Peter, all,
Thank you for the follow-up. I checked 07/10 diff right now. I
like where we are heading with these changes.
I think the only pending point is this one:
“
*/[Med] Thanks for clarifying. The implication is that we need to
discuss whether we update RFC9350 and
draft-ietf-lsr-flex-algo-bw-con so that the selection steps are
now authoritatively offloaded to the registry./*
##PP2
sure, I make this document to updat/e RFC9530/
“
Can we then make that change, please? Thanks.
##PP
posted version 11 that has the update for the 9350. Will add the
draft-ietf-lsr-flex-algo-bw-con once it's published as RFC*/./*
Also, I remember that Les mentioned that the WG wanted to cover
Experimental attributes/algos there as well. I think explicitly
tagging these as such in the registry would be useful. However, I
leave it to decide if you to make the change or not :-)
##PP
experimental algos/attributes are not related to the calculation rules
defined in this registry.
thanks,
Peter
Cheers,
Med
*De :*Peter Psenak <[email protected]> <mailto:[email protected]>
*Envoyé :* lundi 14 juillet 2025 11:16
*À :* BOUCADAIR Mohamed INNOV/NET <[email protected]>
<mailto:[email protected]>; The IESG <[email protected]>
<mailto:[email protected]>
*Cc :* [email protected];
[email protected]; [email protected]; [email protected]
*Objet :* Re: Mohamed Boucadair's Discuss on
draft-ietf-lsr-igp-flex-algo-reverse-affinity-07: (with DISCUSS
and COMMENT)
Hi Med,
please see inline (##PP2):
On 08/07/2025 12:11, [email protected] wrote:
Hi Peter,
Thank you for the follow-up.
Please see inline.
Cheers,
Med
*De :*Peter Psenak <[email protected]>
<mailto:[email protected]>
*Envoyé :* mardi 1 juillet 2025 16:36
*À :* BOUCADAIR Mohamed INNOV/NET
<[email protected]>
<mailto:[email protected]>; The IESG
<[email protected]> <mailto:[email protected]>
*Cc :* [email protected];
[email protected]; [email protected]; [email protected]
*Objet :* Re: Mohamed Boucadair's Discuss on
draft-ietf-lsr-igp-flex-algo-reverse-affinity-07: (with
DISCUSS and COMMENT)
Hi Mohamed,
thanks for your comments, please see responses inline (##PP):
On 30/06/2025 14:17, Mohamed Boucadair via Datatracker wrote:
Mohamed Boucadair has entered the following ballot position for
draft-ietf-lsr-igp-flex-algo-reverse-affinity-07: 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 tohttps://www.ietf.org/about/groups/iesg/statements/handling-ballot-positions/
for more information about how to handle DISCUSS and COMMENT
positions.
The document, along with other ballot positions, can be found here:
https://datatracker.ietf.org/doc/draft-ietf-lsr-igp-flex-algo-reverse-affinity/
----------------------------------------------------------------------
DISCUSS:
----------------------------------------------------------------------
Hi Peter, Jakub, and Amit,
Thank you for the effort put into this specification.
I was surprised that the document does not cite "similar" work on
revere metric
such as in RFC8500 and RFC9339. I'm not saying this is identical,
but there are
similarities that are worth to acknowledge.
##PP
above mention RFCs alter the local IGP metric from the reverse
side of the link. They do that by sending extra data in the
protocol Hello packets that overwrite the locally configured
metric on the link.
What we do in this draft is different. We define a new
flex-algo constraint, which is using the link affinities that
are set locally on the link. Nothing is sent from the other
side of the link that would alter any local link properties.
Link affinities are advertised in a traditional way inside the
LSA/LSP when the router describe its local links. The new
constraint that we defined uses these affinities. On tpp of
looking at the affinities in the forward direction of the
computation, it is now allowed to look at the link affinities
associated with the backward directions of the computation.
*/[Med] Sure. The underlying mechanics differ and, as
indicated in my comment I agree that these are not the same.
Having some text to position the present work vs these RFCs
would be helpful. I won’t insist on making any change here as
that was a meta comment :-)/*
Please find below some points that I think need to be discussed.
# Stability & Lack of Operations Considerations
The activation of the attributes defined in this document may have
implications
on the stability of the routine table. However, the document does not
discuss
such implications, does not include guards to avoid frequent reverse
link
updates, does not provide a guidance about how/when it is safe to make
an
update, does not discuss relevant configuration matters.
Worse, the document does only include an example (as part of use case)
about
how an operator can decide to trigger such message which relies on a
threshold-based approach:
Section 3:
An operator
might monitor metrics like CRC errors or other input-related faults
at node B and apply thresholds over a defined observation period.
If
such a threshold is exceeded, node B may locally assign specific
Extended Administrative Groups to the link in the direction from B
to
A.
Absent robust hysteresis, it is risky to use such threshold-based
approach as
this may lead to instability. FWIW, draft-ietf-nmop-terminology
rightfully
warrant against issues that might be induced by threshold-based schemes:
The use of threshold-driven
Events and States (and the Alerts that they might give rise to) must
be treated with caution to dampen any "flapping" (so that consistent
States may be observed) and to avoid overwhelming management
processes or systems.
##PP
I don't consider RFCs an educational documents, nor
implementation guides. RFCs are written to maintain
interoperability.
*/[Med] but…safe to use as well. Impact on stability is
important for this case./*
This draft specifies protocol extensions that add additional
constraints to the flex-algo computation. It does not even add
any
new link attribute, it uses an existing one. I don't see why
we should talk about how an existing affinity attribute should be
set, just because we find a new use case for it.
There are many scenarios why an IGP may need to
add/remove/modify data in its protocol packets and if not done
correctly
could impact the stability of the network. Standard mechanisms
exists in the IGP protocols to avoid instability caused
by the broken originator, whether it is caused by the poor
implementation or a bug in it.
*/[Med] Would it harm if you remind these “standard” guards?/*
##PP2
I can add a simple statement about the stability aspect, but I
would rather avoid providing any specific solutions on how to
achieve it, as that is not what this document tries to standardize.
Please consider adding a discussion to cover these matters. At minimum,
a
reminder of the considerations in rfc9350#section-15 should be included.
##PP
this draft extends the RFC9350. It does not alter section 15
in any way. I do not understand why do you believe we need to
mention it here.
*/[Med] As we are extending 9350, we need to check that the
ops provisions defined there are altered or not. If there is
no implications, let’s say so explicitly. Thanks. /*
##PP2
not sure I got it, do you want to say that "this document does not
alter section 15 of RFC9350 "? Are we going to say that for every
section of RFC9350 that is not updated?
The document already explicitly says which section it updates:
"The following procedures augment the rules defined in Section 13
of [RFC9350 <https://www.rfc-editor.org/info/rfc9350>] by
introducing additional constraints based on Administrative Groups
(AGs) associated with the reverse direction of a link."
I
suggest you also look at rfc8500#section-3.5, rfc9339#section-7, and
rfc9339#section-8 to see to what extent the ops considerations
discussed out
there are relevant in this specific context.
##PP
I see no relevance of the above RFCs/sections to what we are
specifying here.
We do not alter any local link property based on something
that we receive from the other side, which is what the above
two RFCs do.
*/[Med] ACK/*
# IGP Flex-Algo Path Computation Rules Registry
Unless I’m mistaken, this registry is not specific to this
specification.
What is the rationale for adding this registry here?
##PP
This registry is specific to flex-algo technology, that has
been defined in RFC9350.
Section 13 of that RFC specifies the ordered set of rules that
MUST be followed when the algo specific calculation is done.
Additional rules have been added by this drat and also by
draft-ietf-lsr-flex-algo-bw-con. More changes are on the way.
We realized that it would be difficult for people to find the
latest set of rules without the centralized registry that
keeps track of all changes in these rules.
So we created the registry in this draft. Do you see a problem?
*/[Med] Thanks for clarifying. The implication is that we need
to discuss whether we update RFC9350 and
draft-ietf-lsr-flex-algo-bw-con so that the selection steps
are now authoritatively offloaded to the registry./*
##PP2
sure, I make this document to updat/e RFC9530/
How this registry is
intended to be used/maintained?
##PP
the same way as any other registry that uses "“Expert Review”
registration policy.
*/[Med] :-) My question is more on the practicalities: for
example, do we allow DEs to reorder of steps, merge steps,
insert a step between existing ones, delete steps, altern a
step, etc. /*
##PP2
we can only do what is backward compatible. We will provide the
"guidance" based on the discussion you have had with Les on this
thread.
Why “Expert Review” is picked as policy for
this registry, while all the steps were/are defined in PS
documents? Are DEs
allowed to delete/modify/merge/reorder steps? What are the
implications on
already specified metrics?
##PP
If you look at all ISIS IANA registries, their registration
policy is "Expert Review". Similarly many registries under
"Interior Gateway Protocol (IGP) Parameters" use the same policy.
I have no issues to change it to SA, but we have been happily
using "Expert Review" with IGP registries for many years and
it has worked well.
*/[Med] Given the implications on already existing
implementations, I think Standard Actions makes sense here. /*
----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------
# Illustration examples
Consider adding some examples to illustrate the intended use.
##PP
what exactly do you want me to illustrate? Is the use case not
clearly described?
*/[Med] What I had in mind is an illustrative example with
some few routers to show how the procedure is put into effect
to ensure path symmetry. Thanks./*
##PP2
There is no need for path symmetry here. I still do not understand
your ask here.
thanks,
Peter
# Sections 4/5: Simplify as the types are already assigned.
OLD:
Type (1 octet): An 8-bit field assigned by IANA to uniquely
identify the ISIS FAERAG Sub-TLV. Value 10 has been
assigned by
IANA.
NEW:
Type (1 octet): 10
##PP
done
*/[Med] Thanks/*
OLD:
Type (2 octets): A 16-bit field assigned by IANA to uniquely
identify the OSPF FAERAG Sub-TLV. Value 10 has been
assigned by
IANA.
NEW:
Type (2 octets): 10
##PP
done
*/[Med] ACK/*
# Section 11.1: Use the correct name of the IANA registry +
indicate the registry group
OLD:
IANA has assigned the following Sub-Sub-TLVs in the "ISIS
Sub-Sub-
TLVs for Flexible Algorithm Definition Sub-TLV" registry:
NEW:
IANA has assigned the following Sub-Sub-TLVs in the " IS-IS
Sub-Sub-TLVs
for Flexible Algorithm Definition Sub-TLV" registry under
“IS-IS TLV Codepoints”
registry group:
##PP
done
*/[Med] ACK/*
# Section 11.2: Use the correct name of the IANA registry +
indicate the registry group
OLD:
IANA has assigned the following Sub-TLVs in the "OSPF TLVs for
Flexible Algorithm Definition TLV" registry:
NEW:
IANA has assigned the following Sub-TLVs in the " OSPF Flexible
Algorithm Definition TLV Sub-TLVs" registry under “Open
Shortest Path First (OSPF) Parameters”
registry group:
##PP
done
*/[Med] ACK/*
# Section 11.2: nit
OLD: Description: Flexible Algorithm Include-All ReverseAdmin Group
NEW: Description: Flexible Algorithm Include-All Reverse Admin Group
##PP
fixed
*/[Med] Thanks./*
thanks,
Peter
Cheers,
Med
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