The Time Zone Information Format (TZif)
draft-murchison-tzdist-tzif-16

[Ballot comment]
Updating to remove my Discuss position, as I am confident that it can be
resolved (e.g., via an RFC Editor note).  The original point was:

This is a very boring, almost-trivial discuss point, but the document seems to have
an internal inconsistency to resolve before publication:

Section 3.1 says that the typecnt "MUST NOT be zero", but Section 3.2 says:

  A TZif data block consists of seven variable-length elements, each of
  which is series of zero or more items.  [...]

This is in conflict with the above "MUST NOT be zero" for typecnt.
I don't have a better suggestion than adding a parenthetical "(except for
the local time records, which as mentioned above cannot have zero items)",
even though I acknowledge that it is pretty awkward.

Original COMMENT section:

Section 2

  Coordinated Universal Time (UTC):  The basis for civil time since
      1960.  It is approximately equal to mean solar time at the prime
      meridian (0 degrees longitude).

Usually when "approximately" is used I ask for some quantification/bounds,
but I guess we can skip that for this well-known case.

Section 3.2

  transition types:  A series of one-octet unsigned integers specifying
      the type of local time of the corresponding transition time.
      These values serve as indices into the array of local time type
      records.  The number of type indices is specified by the 'timecnt'
      field in the header.  Each type index MUST be in the range [0,
      'typecnt' -1].

Please specify that the array accesses are zero-indexed.  (Also for
(desig)idx.)

      (is)dst:  A one-octet value indicating whether local time should
        be considered Daylight Savings Time (DST).  The value MUST be 0

nit: just "Daylight Saving"

Section 5.1

nit(?): some readers might interpret the "truncation range" to be "the
range that is truncated, i.e., omitted, from the file" as opposed to "the
range after truncation".  I guess one could make the same claim about the
phrase "truncated range" as well, so maybe no action is the best plan,
here.

Section 7

I also agree with Adam about the privacy considerations -- while the
contents of the file are not the concern, the metadata surrounding which
files go where have privacy implications worth mentioning.

[Ballot discuss]
This is a very boring, almost-trivial discuss point, but the document seems to have
an internal inconsistency to resolve before publication:

Section 3.1 says that the typecnt "MUST NOT be zero", but Section 3.2 says:

  A TZif data block consists of seven variable-length elements, each of
  which is series of zero or more items.  [...]

This is in conflict with the above "MUST NOT be zero" for typecnt.
I don't have a better suggestion than adding a parenthetical "(except for
the local time records, which as mentioned above cannot have zero items)",
even though I acknowledge that it is pretty awkward.

[Ballot comment]
Section 2

  Coordinated Universal Time (UTC):  The basis for civil time since
      1960.  It is approximately equal to mean solar time at the prime
      meridian (0 degrees longitude).

Usually when "approximately" is used I ask for some quantification/bounds,
but I guess we can skip that for this well-known case.

Section 3.2

  transition types:  A series of one-octet unsigned integers specifying
      the type of local time of the corresponding transition time.
      These values serve as indices into the array of local time type
      records.  The number of type indices is specified by the 'timecnt'
      field in the header.  Each type index MUST be in the range [0,
      'typecnt' -1].

Please specify that the array accesses are zero-indexed.  (Also for
(desig)idx.)

      (is)dst:  A one-octet value indicating whether local time should
        be considered Daylight Savings Time (DST).  The value MUST be 0

nit: just "Daylight Saving"

Section 5.1

nit(?): some readers might interpret the "truncation range" to be "the
range that is truncated, i.e., omitted, from the file" as opposed to "the
range after truncation".  I guess one could make the same claim about the
phrase "truncated range" as well, so maybe no action is the best plan,
here.

Section 7

I also agree with Adam about the privacy considerations -- while the
contents of the file are not the concern, the metadata surrounding which
files go where have privacy implications worth mentioning.

[Ballot comment]
I share Spencer's confusion about whether this is documenting something that exists, or if it is defining new things. I think a section with a little background, and possibly an explanation of the history of the 3 mentioned versions, would be helpful.

(Note that, if the answer is that it is defining (some) new things, I kind of wish this had been a working group document. But I'm not going to push that point this late in the process.)

I agree with Adam's concern about privacy. Are there any use cases where a TZIF object might be associated with a person? (For example, I know people who run scripts to insert their current time zone in their XMPP status.) If so, that might imply geolocation information, which is definitely privacy sensitive.

Otherwise, I have a few editorial comments:

§3: "... data specific to version
N+1 either typically appears after version N data..."
Does "typically" imply "not always? I realize there are two choices in the paragraph, but are there cases where neither are true?

§4: "These recommended practices should be followed..."
That language seems to weaken the MUST in the second bullet.

[Ballot comment]
I'm a little confused on one high-level point. In this text,

  This document defines the Time Zone Information Format (TZif).  It is
  a binary format used by most UNIX systems to calculate local time.
  There is a wide variety of interoperable software [tz-link] capable
  of generating and reading files in this format.

is it correct to say that you're documenting the existing format, or are you also defining aspects that are not currently deployed (which would obviously be "defining")?

[Ballot comment]

Thanks for the work everyone did on this document.

---------------------------------------------------------------------------

§7:

I'm glad to see a privacy considerations section in this document. I do
think, however, that it overlooks a relatively major point. The reasons that a
client might choose to download a time zone other than the one it is currently
in will frequently pertain to upcoming locations that its users are going to
be in. While the specific time frame for such a visit won't be indicated, this
information is likely to be perceived by users as very privacy sensitive. I
believe this document should recommend that time zone retrieval be performed
over a confidential channel.

---------------------------------------------------------------------------

§3.2:

>  verrsion 2+ data block.

Nit: "version"

---------------------------------------------------------------------------

General:

The format described by this document is rather complex in some ways. I think it
would be a great aid to implementors if the document included an example,
especially if it were annotated.

(Via drafts-lastcall@iana.org): IESG/Authors/WG Chairs:

The IANA Functions Operator has completed its review of draft-murchison-tzdist-tzif-13. If any part of this review is inaccurate, please let us know.

The IANA Functions Operator understands that, upon approval of this document, there is a single action which we must complete.

In the application registry on the Media Types registry page located at:

https://www.iana.org/assignments/media-types/

two, new media types will be registered as follows:

Name: tzif
Template: [ TBD-at-Registration ]
Reference: [ RFC-to-be ]

Name: tzif-leap
Template: [ TBD-at-Registration ]
Reference: [ RFC-to-be ]

The IANA Functions Operator understands that this is the only action required to be completed upon approval of this document.

Note:  The actions requested in this document will not be completed until the document has been approved for publication as an RFC. This message is meant only to confirm the list of actions that will be performed.

Thank you,

Sabrina Tanamal
Senior IANA Services Specialist

The following Last Call announcement was sent out (ends 2018-10-09):

From: The IESG
To: IETF-Announce
CC: lear@ofcourseimright.com, alexey.melnikov@isode.com, tzdist-bis@ietf.org, draft-murchison-tzdist-tzif@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (The Time Zone Information Format (TZif)) to Proposed Standard


The IESG has received a request from an individual submitter to consider the
following document: - 'The Time Zone Information Format (TZif)'
  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
ietf@ietf.org mailing lists by 2018-10-09. 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 document defines the Time Zone Information Format (TZif) for
  representing and exchanging time zone information, independent of any
  particular service or protocol.  Two MIME media types for this format
  are also defined.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-murchison-tzdist-tzif/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-murchison-tzdist-tzif/ballot/


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

> (1) What type of RFC is being requested (BCP, Proposed Standard,
> Internet Standard, Informational, Experimental, or Historic)? Why is
> this the proper type of RFC? Is this type of RFC indicated in the
> title page header?
>
Proposed Standard.

> (2) The IESG approval announcement includes a Document Announcement
> Write-Up. Please provide such a Document Announcement Write-Up. Recent
> examples can be found in the "Action" announcements for approved
> documents. The approval announcement contains the following sections:
>
> Technical Summary
>
> Relevant content can frequently be found in the abstract and/or
> introduction of the document. If not, this may be an indication that
> there are deficiencies in the abstract or introduction.

  This document defines the Time Zone Information Format (TZif) for
  representing and exchanging time zone information, independent of
  any particular service or protocol.  Two MIME media types for this
  format are also defined.  Note that this format has existed for
  over three decades in one form or another.

>
> Working Group Summary
>
> Was the document considered in any WG, and if so, why was it not
> adopted as a work item there? Was there controversy about particular
> points that caused the WG to not adopt the document?

This document was not considered by any existing working group. The AD
considered creating a WG, but it was thought that things were moving
quickly enough with the right people without one.


>
> Document Quality
>
> Are there existing implementations of the protocol? Have a significant
> number of vendors indicated their plan to implement the
> specification?

This format is widely deployed.

> Are there any reviewers that merit special mention as having done a
> thorough review, e.g., one that resulted in important changes or a
> conclusion that the document had no substantive issues? If there was a
> MIB Doctor, Media Type or other expert review, what was its course
> (briefly)? In the case of a Media Type review, on what date was the
> request posted?

Ned Freed did a media-type review on June 6, 2018.  However, a second
review is requested, as the media-type entries have changed.

>
> Personnel
>
> Who is the Document Shepherd? Who is the Responsible Area Director?

Eliot Lear is the Shepherd.  Alexey Melnikov is the responsible AD.

>
> (3) Briefly describe the review of this document that was performed by
> the Document Shepherd. If this version of the document is not ready
> for publication, please explain why the document is being forwarded to
> the IESG.

The shepherd has implemented the draft (sans leap seconds) to validate it.

>
> (4) Does the document Shepherd have any concerns about the depth or
> breadth of the reviews that have been performed?

Not yet.

>
> (5) Do portions of the document need review from a particular or from
> broader perspective, e.g., security, operational complexity, AAA, DNS,
> DHCP, XML, or internationalization? If so, describe the review that
> took place.


Additional media-type review, ART, Security, Ops, GenART.


>
> (6) Describe any specific concerns or issues that the Document
> Shepherd has with this document that the Responsible Area Director
> and/or the IESG should be aware of? For example, perhaps he or she is
> uncomfortable with certain parts of the document, or has concerns
> whether there really is a need for it. In any event, if the interested
> community has discussed those issues and has indicated that it still
> wishes to advance the document, detail those concerns here.

The leap second processing text is intricate, especially when
truncation occurs.  The mailing list spent an extensive amount of
time on this aspect, and there is consensus on what is there now.
This having been said, additional operational experience will bear out
whether it is properly interpreted over time.  Having multiple existing
implementations, at least one of which is open source should mitigate
this risk.

>
> (7) Has each author confirmed that any and all appropriate IPR
> disclosures required for full conformance with the provisions of BCP
> 78 and BCP 79 have already been filed. If not, explain why.

Yes.

>
> (8) Has an IPR disclosure been filed that references this document? If
> so, summarize any discussion and conclusion regarding the IPR
> disclosures.

No.

>
> (9) How solid is the consensus of the interested community behind this
> document? Does it represent the strong concurrence of a few
> individuals, with others being silent, or does the interested
> community as a whole understand and agree with it?

Among the small community of participants, there is strong consensus.

>
> (10) Has anyone threatened an appeal or otherwise indicated extreme
> discontent? If so, please summarise 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 one has threatened to appeal, nor is there at this point disagreement.


> (11) Identify any ID nits the Document Shepherd has found in this
> document. (See http://www.ietf.org/tools/idnits/ and the
> Internet-Drafts Checklist). Boilerplate checks are not enough; this
> check needs to be thorough.

There are a few nits, but these appear to be the nits tool and not the
document.  In particular, the document isn't properly recognizing
different types or references or the updated 2119 boiler template, and
it is parsing URLs in the references section and complaining that
there is no reference.


>
> (12) Describe how the document meets any required formal review
> criteria, such as the MIB Doctor, media type, and URI type reviews.

Review performed by a designated expert, but see above.

>
> (13) Have all references within this document been identified as
> either normative or informative?

Yes.

>
> (14) Are there normative references to documents that are not ready
> for advancement or are otherwise in an unclear state? If such
> normative references exist, what is the plan for their completion?

No.

>
> (15) Are there downward normative references references (see RFC
> 3967)? If so, list these downward references to support the Area
> Director in the Last Call procedure.

Not unless we view POSIX as a downref.

>
> (16) Will publication of this document change the status of any
> existing RFCs? Are those RFCs listed on the title page header, listed
> in the abstract, and discussed in the introduction? If the RFCs are
> not listed in the Abstract and Introduction, explain why, and point to
> the part of the document where the relationship of this document to
> the other RFCs is discussed. If this information is not in the
> document, explain why the interested community considers it
> unnecessary.

This document does not change the status of any other work.

>
> (17) 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 protocol extensions that
> the document makes are associated with the appropriate reservations in
> IANA registries. Confirm that any referenced IANA registries have been
> clearly identified. Confirm that newly created IANA registries include
> a detailed specification of the initial contents for the registry,
> that allocations procedures for future registrations are defined, and
> a reasonable name for the new registry has been suggested (see RFC
> 5226).

No new registries are created.  Existing registries are updated in
accordance with appropriate templates and procedures, but see above
re the media-type.


>
> (18) List any new IANA registries that require Expert Review for
> future allocations. Provide any public guidance that the IESG would
> find useful in selecting the IANA Experts for these new registries.
>

n/a

> (19) Describe reviews and automated checks performed by to validate
> sections of the document written in a formal language, such as XML
> code, BNF rules, MIB definitions, etc.
>

This document does not specify formal grammar, but a file format.  As
such, no XML, BNF, or MIB definitions exist.