Hello Greg, Jorge, All,
I support these changes.
In section 7.11.1 it is the previos reference to the Control Word that needs to
be modified:
OLD TEXT
The EVPN L2-Attr Extended Community, when added to Inclusive
Multicast route:
* per-EVI attributes MTU, Control Word and Flow Label are conveyed,
and;
* per-ESI-and-EVI attributes P, B MUST be zero.
NEW TEXT
The EVPN L2-Attr Extended Community, when added to Inclusive
Multicast route:
* per-EVI attributes MTU, Control Word (SHOULD be set to 1) and Flow
Label are conveyed,
and;
* per-ESI-and-EVI attributes P, B MUST be zero.
As Jorge mentioned, when the EVPN L2-Attr Extended Community is included on
Ethernet A-D per
EVI route then the MTU, Control Word and Flow Label are not in use so that
is why “they MUST be zero”, in the second reference to these bits in Section
7.1.1
============
In addition to what you have written below on Section 18:
In my opinion, the following sentence should either be removed or updated:
OLD TEXT
If a network (inclusive of all PE and P nodes) uses entropy labels
per [RFC6790] for ECMP load balancing, then the control word MAY
NOT be used.
NEW TEXT
If a network (inclusive of all PE and P nodes) uses entropy labels
per [RFC6790] for ECMP load balancing, then the control word SHOULD still
be used.
===============
In addition RFC 8214 needs to be addressed. This was also mentioned at the IETF
Meeting in Brisbane.
Thank you kindly.
Best Regards,
Menachem
From: BESS <[email protected]> on behalf of Greg Mirsky
<[email protected]>
Date: Friday, 22 March 2024 at 3:07
To: Jorge Rabadan (Nokia) <[email protected]>
Cc: [email protected] <[email protected]>,
[email protected] <[email protected]>, MPLS
Working Group <[email protected]>, [email protected]
<[email protected]>, [email protected] <[email protected]>
Subject: Re: [bess] PFN questions in rfc4732bis
CAUTION: External E-Mail - Use caution with links and attachments
Hi Jorge,
thank you for your expedient feedback to the proposed updates. I have several
follow-up notes logged below under the GIM>> tag.
Regards,
Greg
On Fri, Mar 22, 2024 at 9:30 AM Jorge Rabadan (Nokia)
<[email protected]<mailto:[email protected]>> wrote:
Hi Greg,
Thanks for getting back.
My comments in line with [jorge].
Jorge
From: Greg Mirsky <[email protected]<mailto:[email protected]>>
Date: Thursday, March 21, 2024 at 2:41 AM
To:
[email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>,
[email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>,
MPLS Working Group <[email protected]<mailto:[email protected]>>,
[email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>
Subject: PFN questions in rfc4732bis
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for additional information.
Dear All,
following the presentation of our work on the Post-stack First Nibble (PFN) to
the BESS WG at IETF-119, I took an AP to come with questions and proposals for
the authors of rfc4732bis. I thought that once the authors of the respective
drafts converge on the updates, we share them with the BESS WG. Below, please
find my notes:
• rfc4732bis recognizes MPLS Entropy label as a source of entropy for
load-balancing. 1stnibble draft also refers to RFC
6391<https://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.ietf.org_doc_rfc6391_&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=cezglEhs6Oa_CKN9mhFbT8T8kmWwaNdtBDjE9bvBG_E&m=f9mqEJ1P1fyT-GceDqOAwZOtLN9vYtkDjjIhXGhqATDiV_HIDj6ioNdEIGZ1iG6E&s=5OAGJEbhyQZ_lv9PWvOvDTUQ7LGgMT9hpw9B5wXj4VQ&e=>
as another optional source of the entropy for load-balancing. Would it be
helpful adding a refgerence to RFC 6391 in the discussion of the load-balancing
in rfc4732bis?
[jorge] that should be fine.
• The definition of the C flag in Section 7.11 is as follows:
C If set to 1, a control word [RFC4448] MUST be present
when sending EVPN packets to this PE. It is
recommended that the control word be included in the
absence of an entropy label [RFC6790].
To reflect the position expressed in the 1stnibble draft, perhaps the following
update is appropriate:
NEW TEXT:
C If set to 1, a control word [RFC4448] MUST be present
when sending EVPN packets to this PE.
END
[jorge] I personally see no issue with the above update if the other co-authors
are ok too.
• Furthermore, the following update may be considered in Section 7.11.1:
OLD TEXT:
* per-ESI-and-EVI attributes P, B are conveyed, and;
* per-EVI attributes MTU, Control Word and Flow Label MUST be zero.
NEW TEXT:
* per-ESI-and-EVI attributes P, B are conveyed;
* per-EVI attributes MTU, and Flow Label MUST be zero, and;
* per-EVI attribute Control Word MUST be set.
[jorge] I don’t think the above change is correct. The reason is this refers to
the L2 attributes extended community sent along with the AD per EVI routes in
EVPN ELAN services (not EVPN VPWS), and this route is purely used for
multi-homing. The non-multihoming related attributes MUST be zero, since they
are signaled along with the inclusive multicast ethernet tag route. So the
current text is correct.
GIM>> I acknowledge that the use of the Control Word in this scenario that I am
not familiar with. The motivation for proposing this update is based on my
itnerpretation of the definition of the C flag in Section 7.11 (see above) and
the intention of the draft-ietf-mpls-1stnibble to deprecate the use of non-PSH
encapsulations of non-IP payload. As I understand the current text in question,
by setting the Control Word to zero the control plane will produce packets
without PSH (PW CW). If that is correct, then that is precisely what our work
on the PFN aims to exclude.
• The text in Section 18, following the first paragraph, may be
replaced with the following text:
NEW TEXT:
In order to avoid frame misordering described in the above paragraph,
and following conclusions of [I-D.ietf-mpls-1stnibble], the control word
MUST be used in all use cases.
END
[jorge] so basically you are suggesting to use CW always and use MUST as
normative language, irrespective of a) the underlaying transport, b) whether
entropy label is used and c) whether deep packet inspection for ECMP is used.
The only problem that I see is that, till now, implementations not supporting
CW were still compliant with RFC7432 and this bis draft. Now it would not be
the case anymore.
I personally think it might be better to use a SHOULD, e.g.:
NEW:
In order to avoid frame misordering described in the above paragraph,
the control word SHOULD be used in all use cases [I-D.ietf-mpls-1stnibble].
END
But I’d like to hear from other coauthors and the BESS WG to see if this is ok.
Finally, if we were to add [I-D.ietf-mpls-1stnibble] as a reference, it would
be an informative reference.
GIM>> We've used SHOULD in RFC
8469<https://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.ietf.org_doc_html_rfc8469&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=cezglEhs6Oa_CKN9mhFbT8T8kmWwaNdtBDjE9bvBG_E&m=f9mqEJ1P1fyT-GceDqOAwZOtLN9vYtkDjjIhXGhqATDiV_HIDj6ioNdEIGZ1iG6E&s=TWTOL85TMzc33zd31_A7GIj_GuBBrPesJZflBXCJ3DQ&e=>,
and believe that it is time to deprecate the practice of non-PSH encapsulation
of non-IP payload in MPLS altogether, and use PSH/CW in all scenarios for
non-IP payload. I'll note that the deprecation, as defined in
draft-ietf-mpls-1stnibble, applies only to new deployments and implementations.
(I believe that an intellegent implementation that supports non-PSH(non-CW)
encapsulation is also capable of using PW CW encapsulation.)
Please share you questions, comments, and suggestions.
Regards,
Greg
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