HTTP Cache Groups
draft-ietf-httpbis-cache-groups-07

Received changes through RFC Editor sync (changed state to RFC, created became rfc relationship between draft-ietf-httpbis-cache-groups and RFC 9875, changed IESG state to RFC Published)

[Ballot comment]
As Mark has stated he will change the example and my other concern is no longer valid, I am changing my ballot to No Objection.

[Ballot comment]
"Abstract", paragraph 0
>    This specification introduces a means of describing the relationships
>    between stored responses in HTTP caches, "grouping" them by
>    associating a stored response with one or more opaque strings.

The ballot text for this document still refers to Francesca as the Responsible AD. That should be fixed.

-------------------------------------------------------------------------------
NIT
-------------------------------------------------------------------------------

All comments below are about very minor potential issues that you may choose to
address in some way - or ignore - as you see fit. Some were flagged by
automated tools (via https://github.com/larseggert/ietf-reviewtool), so there
will likely be some false positives. There is no need to let me know what you
did with these suggestions.

Section 1, paragraph 5
> oduces one new source of such events: a HTTP response header field that allow
>                                      ^
Use "an" instead of "a" if the following word starts with a vowel sound, e.g.
"an article", "an hour".

[Ballot comment]
Thanks to Barry Lieba for the secdir review.

Section 3, example:  I agree with Andy Newton's  "your fav pop star' discuss.  There are so many options to choose from, it would seem possible and prudent to pick an obviously fictional example. (It is reported that Kylie Minogue has never been on Eurovision, even though Australia is a member).

[Ballot comment]
Nice, easy to read, and useful document.

Just one comment, when reading "opaque" I was expecting an apparently meaningless string, e.g., a hash of something, but readable strings are used in the examples. Should there be some operational guidance on the 'group' string (meaningful vs. random strings) ?

[Ballot discuss]
# Andy Newton, ART AD, comments for draft-ietf-httpbis-cache-groups-05
CC @anewton1998

* line numbers:
  - https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-httpbis-cache-groups-05.txt&submitcheck=True

* comment syntax:
  - https://github.com/mnot/ietf-comments/blob/main/format.md

* "Handling Ballot Positions":
  - https://ietf.org/about/groups/iesg/statements/handling-ballot-positions/

## Discuss

As noted in https://www.ietf.org/blog/handling-iesg-ballot-positions/,
a DISCUSS ballot is just a request to have a discussion on the following topics:

Thanks for writing this document. It is very well written and easy to read.

### Your Fav Pop Star HERE

I hate to be that guy, but...

187        Cache-Group-Invalidation: "eurovision-results", "kylie-minogue"

TIL that Australia is a member of the EBU and therefore this is a logical grouping,
however does this document require the use of real people and organizations to
create an interoperable specification?

### Maximum Length

I see that minimum lengths are set:

205        Implementations MUST support at least 32 groups in a field value,
206        with up to at least 32 characters in each member.  Note that generic
207        limitations on HTTP field lengths may constrain the size of this
208        field value in practice.

However, no maximum field or string lengths are set. I see this in RFC 9651:

    This specification defines minimums for the length or number of
    various structures supported by implementations. It does not specify
    maximum sizes in most cases, but authors should be aware that HTTP
    implementations do impose various limits on the size of individual
    fields, the total number of fields, and/or the size of the entire
    header or trailer section.

Should this document set maximums? If not, is the expected behavior that the headers are ignored?

[Ballot comment]
Hi Mark,

Thank you for this well-written document.

Please find below some comments:

# (nit) consider split this long sentence:

OLD:
  In addition to sharing invalidation events, the relationships
  indicated by grouping can also be used by caches to optimise their
  operation; for example, it could be used to inform the operation of
  cache eviction algorithms.

NEW
  In addition to sharing invalidation events, the relationships
  indicated by grouping can also be used by caches to optimise their
  operation. For example, it could be used to inform the operation of
  cache eviction algorithms.

# (nit)

OLD: Section 3 introduces one new source of such events: a HTTP response

NEW: Section 3 introduces one new source of such events: an HTTP response

# Same origin

CURRENT:
  These mechanisms operate within a single cache, across the stored
  responses associated with a single origin server . 

Do we need to say how that "single origin server" is identified?

# Mention the section where to look at

CURRENT:
  The Cache-Groups HTTP Response Header is a List of Strings
  [STRUCTURED-FIELDS]. 

and

CURRENT:
  The Cache-Group-Invalidation response header field is a List of
  Strings [STRUCTURED-FIELDS]. 

Please add a reference to the exact section to look at.

As we don’t have a clear reference, I don't know whether we allow empty values? Same value repeated several times? upper case, etc.

# Parameters

CURRENT:
  The ordering of members is not significant.  Unrecognised Parameters
  MUST be ignored.

Which parameters?

Also, shouldn’t the validation be based on RFC8941 to avoid redundant behaviors? That is, do we need this MUST?

# Lack of reasoning

CURRENT:
  Implementations MUST support at least 32 groups in a field value ,
  with up to at least 32 characters in each member.  Note that generic
  limitations on HTTP field lengths may constrain the size of this
  field value in practice.

and

CURRENT:
  Implementations MUST support at least 32 groups in a field value,
  with up to at least 32 characters in each member.  Note that generic
  limitations on HTTP field lengths may constrain the size of this
  field value in practice.

What is the rationale for picking these values? What is currently supported by existing implementations? Can this be configurable? How one can retrieve what is supported by a given implementation?

# (nit) Both items

OLD: the same group when all of the following conditions are met

NEW: the same group when both of the following conditions are met

# Comparison logic

CURRENT:
  1.  They both contain a Cache-Groups response header field that
      contains the same String (in any position in the List), when
      compared character-by-character .

Is the comparison case-sensitive? Or do we rely on rfc8941 for these matters, e.g., to prevent upper case to be used in a list item?

# Reasoning again

CURRENT:
  A cache that receives a Cache-Group-Invalidation header field on a
  response to an unsafe request MAY invalidate any stored responses
  that share groups (per Section 2.1) with any of the listed groups.

What is the rationale for the MAY here?

# Interaction with proxies

How this mechanism interacts with proxies? Are those allowed to inject/alter what is set by a server?

May be adding a reference where such «generic» matters are covered would be useful here.

# Management

CURRENT:
  (sometimes referred to as "shared hosting") might allow one party to
  group its resources with those of others, or to send signals which
  have side effects upon them.

How that is managed by a "party" in practice? Is it a configuration action?

# Cascaded effect

If we have an entry that belongs to A/B, another that belongs to B/C, and a third to C/D. If A group is invalidated, this will impact the second entry per the rules in 2.2.1. However, does this impact the third one as well is it shares a group with the second invalidated one?

Cheers,
Med

[Ballot comment]
Thanks for this document. It's well-written and helps standardize behavior that many CDNs already do in proprietary ways.

- https://github.com/httpwg/http-extensions/pull/3016 addresses Last Call feedback and has not yet been merged.
- https://github.com/httpwg/http-extensions/issues/2933 has not been addressed.

Please incorporate that feedback and publish a new version before the rest of the IESG begins reviewing, if you intend to do so.

[Ballot comment]
- https://github.com/httpwg/http-extensions/pull/3016 addresses Last Call feedback and has not yet been merged.
- https://github.com/httpwg/http-extensions/issues/2933 has not been addressed.

Please incorporate that feedback and publish a new version before the rest of the IESG begins reviewing, if you intend to do so.

The following Last Call announcement was sent out (ends 2025-02-26):

From: The IESG
To: IETF-Announce
CC: draft-ietf-httpbis-cache-groups@ietf.org, francesca.palombini@ericsson.com, httpbis-chairs@ietf.org, ietf-http-wg@w3.org, tpauly@apple.com
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (HTTP Cache Groups) to Proposed Standard


The IESG has received a request from the HTTP WG (httpbis) to consider the
following document: - 'HTTP Cache Groups'
  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 2025-02-26. 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


  This specification introduces a means of describing the relationships
  between stored responses in HTTP caches, "grouping" them by
  associating a stored response with one or more opaque strings.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-httpbis-cache-groups/



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

## 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?

This is a simple document that had good working group support. It mainly applies
to implementors of caches, so it had engagement from a subset of the community,
but had good support there.

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

No controversy on this document.

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 appeals threatened.

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)?

This document represents a standardization of a practice that is common, but
can vary across implementations.

## 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.

No close interactions with other technology.

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.

No such requirements.

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]?

No YANG.

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.

No formal language here. This has HTTP response examples, which look correct.

## 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, I believe this document is ready to progress.

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?

We haven't done specific area reviews, but I don't think it needs one.
Since this is a product of the HTTP group, we don't do a separate HTTPDIR review.

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, since this is a protocol extension.

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.

The author has not disclosed any IPR for this document.

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, the author is willing to be listed.

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.)

No nits found.

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

The references seem appropriate.

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

No non-accessible references.

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.

No updates

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]).

The IANA section registers one HTTP field name, which seems reasonable.

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 new registries.

[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/

## 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?

This is a simple document that had good working group support. It mainly applies
to implementors of caches, so it had engagement from a subset of the community,
but had good support there.

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

No controversy on this document.

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 appeals threatened.

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)?

This document represents a standardization of a practice that is common, but
can vary across implementations.

## 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.

No close interactions with other technology.

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.

No such requirements.

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]?

No YANG.

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.

No formal language here. This has HTTP response examples, which look correct.

## 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, I believe this document is ready to progress.

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?

We haven't done specific area reviews, but I don't think it needs one.
Since this is a product of the HTTP group, we don't do a separate HTTPDIR review.

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, since this is a protocol extension.

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.

The author has not disclosed any IPR for this document.

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, the author is willing to be listed.

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.)

No nits found.

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

The references seem appropriate.

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

No non-accessible references.

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.

No updates

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]).

The IANA section registers one HTTP field name, which seems reasonable.

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 new registries.

[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/