Segment Routing over IPv6 Argument Signaling for BGP Services
draft-ietf-bess-bgp-srv6-args-10

Received changes through RFC Editor sync (changed state to RFC, created became rfc relationship between draft-ietf-bess-bgp-srv6-args and RFC 9819, changed IESG state to RFC Published)

[Ballot comment]

# Éric Vyncke, INT AD, comments for draft-ietf-bess-bgp-srv6-args-08
CC @evyncke

Thank you for the work put into this document.

Please find below some non-blocking COMMENT points (but replies would be appreciated even if only for my own education), and one nit.

Special thanks to Zhaohui (Jeffrey) Zhang for the shepherd's write-up including the WG consensus and the justification of the intended status.

I hope that this review helps to improve the document,

Regards,

-éric

## COMMENTS (non-blocking)

### Abstract

Suggest removing the first sentence.

Possibly add a reference to RFC 8986 network programming as this is specific to net-pgm and not plain SRv6.

### Section 1

s/SRv6 refers to Segment Routing instantiated on the IPv6 data plane/SRv6 refers to Segment Routing instantiated *over* the IPv6 data plane/ ?

*VERY* ambiguous statement `SRv6 Service Segment Identifier (SID) refers to an SRv6 SID` (recursive and conflicting redefinition of SID)

### Section 2

`As specified in [RFC8986], an SRv6 SID comprises three components:` is not correct as RFC 8402 that defines SID has not this structure. So, let's be specific and states that "RFC 8946 SID comprises three components" or something similar.

### Section 3.1

s/Ethernet Auto-Discovery (A-D) ... are utilized/s/Ethernet Auto-Discovery (A-D) ... *is* utilized/ ?

`::0` is not a canonical format for "::".

s/0:0:0:0:aaaa::/::aaaa:0:0:0/ (also in section 3.3)

### Section 3.3

`BUM` is already define before.

### Being more generic ?

Sections 3.1 and 3.2 seems very specific, but should the described mechanism be more generic ? The bit-wise OR seems indeed too simplistic and this mechanism could be used for other end point behavior beyond those described in section 3.1 and 3.2

## NITS (non-blocking / cosmetic)

### Use of SVG graphics

To make a much nicer HTML rendering, suggest using the aasvg too to generate SVG graphics. It is worth a try especially if the I-D uses the Kramdown file format ;-)

[Ballot comment]
Thank you for this document. I have a few nits but nothing major:

  == There are 3 instances of lines with non-RFC3849-compliant IPv6 addresses
    in the document.  If these are example addresses, they should be changed.

16   RFC9252 defines procedures and messages for BGP Services for Segment

Jim> Note that RFC 9252 says “BGP overlay services” not “BGP services”. Can we make this consistent with the cited reference.

74 1.  Introduction

76   SRv6 refers to Segment Routing instantiated on the IPv6 data plane
77   [RFC8402].  SRv6 Service Segment Identifier (SID) refers to an SRv6

Jim> Shouldn’t this be something like (SSID) rather than (SID) as the abbreviation does not align with the text (?). SRv6 Service SID is a type of SID but not the only one so using SID as the abbreviation seems wrong. It would be better to just say “SRv6 Service SID” which is inline with what RFC 9252 does.

83   signaling of BGP services including L3VPN, EVPN, and Internet

Jim> Again, s/BGP services/BGP overlay services

84   services using SRv6 as data plane.

Jim> SRv6 is not really the data plane, IPv6 is. I would suggest to remove “as data plane” and just end the sentence at “SRv6”.

86   For certain EVPN services, [RFC8986] introduced the End.DT2M SRv6
87   Endpoint Behavior, which utilizes arguments (i.e., Arg.FE2).

Jim> Please expand the reference to RFC8986 Section 4.12 which is where End.DT2M is defined in that RFC.

142   As specified in Section 3.2.1 of [RFC9252], the SRv6 SID Structure
143   sub-sub-TLV MUST be included when signaling an SRv6 SID corresponding

Jim> s/SRv6 SID Structure sub-sub-TLV/SRv6 SID Structure Sub-Sub-TLV

397           are both non-zero and but not equal, then no usable ARG value

Jim> s/and but not equal/but not equal

[Ballot comment]
Hi Ketan, Syed, Jorge, & Wen,

Thank you for the effort put into this well-written document.

Also, thanks to Joe Clarke for the OPSDIR review. I noted that Ketan promised a revised version ;-)

The document inherits deployment/ops considerations in RFC9252. The document reasonably includes provisions to ease troubleshooting (logging, in particular). Support of tracing-like capabilities would help detecting when inconsistent structures would be interesting to investigate as future work.

Please find below some comments, many are nits:

# Expand SRv6 in the title/abstract

# The abstract should be self-contained. Consider at least adding title of the cited RFC and expand all acronyms.

# “Internet services”: I know that 9252 uses that term but still I don’t parse it :-) Do we meant “IP Connectivity services”? If so, consider updating that.

# Is there a special meaning associated with “BGP Service”? I see 9252 uses both variants “BGP Services” and “BGP services”, though. Likewise, both flavors are used in this spec. Need some clarity here.

# Section 1

## Do we have any public pointer to cite for “implementation and interoperability testing”?

CURRENT:
  implementation and interoperability testing, it was observed that the
  specifications outlined in [RFC9252] lacked sufficient detail,
  leading to ambiguities in interpretation and implementation.

## Can we cite an example of similar endpoint behavior?

CURRENT:
  described herein are also applicable to other similar endpoint
  behaviors with arguments that may be signaled using BGP.

## (nitty nit) TPOS-O and TPOS-L are not used in RFC9252 as such. I understand that this is introduced here for the illustration examples. Maybe add that note as a legend to one of the example and delete these mentions here:

CURRENT:
  Consequently, the Transposition Offset (TPOS-O) and Transposition
  Length (TPOS-L) are set to zero, and references to MPLS label fields

# Section 2

## nit

OLD:
  For SRv6 SIDs
  associated with SRv6 Endpoint Behaviors that do not support argument

NEW:
  For SRv6 SIDs
  associated with SRv6 Endpoint Behaviors that do not support arguments,

## I don’t think the following a new behavior to justify the use of normative language. Is it?

CURRENT:
    Consequently, all bits following
  the FUNC portion MUST be set to zero, and the argument length MUST be
  zero.

## This is already part of 9252 which is updated by this doc. I don’ think the normative language is justified here.

CURRENT:
  As specified in Section 3.2.1 of [RFC9252], the SRv6 SID Structure
  sub-sub-TLV MUST be included when signaling an SRv6 SID corresponding
  to an endpoint behavior that supports argument. 

## I guess this is using “SRv6 SID Structure Sub-Sub-TLV”. Can we say that in the text?

CURRENT:
  Since arguments may be optional, the SRv6 Endpoint Node that owns the
  SID MUST advertise the SRv6 SID Structure along with the LOC:FUNC

# Section 3.1: Check

CURRENT:
  Since the End.DT2M behavior
  supports the use of an ARG, an SRv6 SID Structure sub-sub-TLV MUST be
  included. 

Isn’t that covered by:

  “the SRv6 Endpoint Node that owns the
  SID MUST advertise the SRv6 SID Structure along with the LOC:FUNC
  portion of the SRv6 SID to indicate whether arguments are supported
  for that specific SID”?

# Section 3.3

## (nit) s/The ingress Provider Edge (PE) router/The ingress PE

## (nit) s/Figure 7 below/Figure 7

# Section 4

OLD: specified in document in Section 3.3 MUST be used to correctly derive the SRv6
NEW: specified in Section 3.3 MUST be used to correctly derive the SRv6

Cheers,
Med

[Ballot comment]
I found no-transport-related concerns in this document.

I have one comment:

“Additionally, as a
  non-zero ARG value is being signaled, the Argument Length (AL) MUST
  be set to the size of the ARG, and the size SHOULD be a multiple of
  8. “
- WHY SHOULD? I may have missed, but did not see any reason why the length is specified this way.
- Perhaps it would be useful to note how receivers are to process an AL size when not a multiple of 8?

IESG/Authors/WG Chairs:

IANA has completed its review of draft-ietf-bess-bgp-srv6-args-06, which is currently in Last Call, and has the following comments:

We understand that this document doesn't require any registry actions.

While it's often helpful for a document's IANA Considerations section to remain in place upon publication even if there are no actions, if the authors strongly prefer to remove it, we do not object.

If this assessment is not accurate, please respond as soon as possible.

For definitions of IANA review states, please see:

https://datatracker.ietf.org/help/state/draft/iana-review

Thank you,

David Dong
IANA Services Sr. Specialist

The following Last Call announcement was sent out (ends 2025-03-04):

From: The IESG
To: IETF-Announce
CC: bess-chairs@ietf.org, bess@ietf.org, draft-ietf-bess-bgp-srv6-args@ietf.org, gunter@vandevelde.cc, zzhang@juniper.net
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (SRv6 Argument Signaling for BGP Services) to Proposed Standard


The IESG has received a request from the BGP Enabled ServiceS WG (bess) to
consider the following document: - 'SRv6 Argument Signaling for BGP Services'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits final
comments on this action. Please send substantive comments to the
last-call@ietf.org mailing lists by 2025-03-04. Exceptionally, comments may
be sent to iesg@ietf.org instead. In either case, please retain the beginning
of the Subject line to allow automated sorting.

Abstract


  RFC9252 defines procedures and messages for SRv6-based BGP services
  including L3VPN, EVPN, and Internet services.  This document updates
  RFC9252 and provides more detailed specifications for the signaling
  and processing of SRv6 SID advertisements for BGP Service routes
  associated with SRv6 Endpoint Behaviors that support arguments.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-bess-bgp-srv6-args/



No IPR declarations have been submitted directly on this I-D.

# https://datatracker.ietf.org/doc/draft-ietf-bess-bgp-srv6-args/

*This version is dated 4 July 2022.*

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

The work has been discussed and agreed among typical/key/active EVPN
participants, including the SRPING WG co-chair Bruno.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

No.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

There are three implementations reported from Cisco, Juniper, and Nokia during
the WGLC.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

This is a signaling update to RFC9252 and does not involve changes in Segment
Routing base technology or BGP base protocol.
Spring/IDR WGs were copied during the WGLC. No responses have been received.
Bruno from thw Srping WG had comments during the WG adoption period and
they were addressed.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

Not required.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

N/A.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

N/A.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Yes.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

No.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

Proposed Standard, and justifed as follows:

  "This document updates [RFC9252] to provide the necessary details and
  clarifications related to the signaling of SRv6 Service SIDs
  corresponding to SRv6 Endpoint Behaviors that use arguments."
 
12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

All co-authors have declared they are unaware of (undisclosed) IPRs.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes. Four co-authors.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

There is one idnits warning:

  == There are 3 instances of lines with non-RFC3849-compliant IPv6 addresses
    in the document.  If these are example addresses, they should be changed.

But that is a false positive about the intentional use of SID: 0:0:0:0:aaaa::.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

No.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

None.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

No.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

No.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

This document updates RFC9252 and that is properly reflected.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

No IANA changes needed.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

No IANA changes needed.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

# https://datatracker.ietf.org/doc/draft-ietf-bess-bgp-srv6-args/

*This version is dated 4 July 2022.*

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

The work has been discussed and agreed among typical/key/active EVPN
participants, including the SRPING WG co-chair Bruno.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

No.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

There are three implementations reported from Cisco, Juniper, and Nokia during
the WGLC.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

This is a signaling update to RFC9252 and does not involve changes in Segment
Routing base technology or BGP base protocol.
Spring/IDR WGs were copied during the WGLC. No responses have been received.
Bruno from thw Srping WG had comments during the WG adoption period and
they were addressed.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

Not required.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

N/A.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

N/A.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Yes.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

No.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

Proposed Standard, and justifed as follows:

  "This document updates [RFC9252] to provide the necessary details and
  clarifications related to the signaling of SRv6 Service SIDs
  corresponding to SRv6 Endpoint Behaviors that use arguments."
 
12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

All co-authors have declared they are unaware of (undisclosed) IPRs.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes. Four co-authors.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

There is one idnits warning:

  == There are 3 instances of lines with non-RFC3849-compliant IPv6 addresses
    in the document.  If these are example addresses, they should be changed.

But that is a false positive about the intentional use of SID: 0:0:0:0:aaaa::.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

No.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

None.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

No.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

No.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

This document updates RFC9252 and that is properly reflected.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

No IANA changes needed.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

No IANA changes needed.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/