Alternatives for Multilevel Transparent Interconnection of Lots of Links (TRILL)
draft-ietf-trill-rbridge-multilevel-07

[Ballot comment]
This document "enumerates and examines alternatives" related to multilevel TRILL.  It provides useful information, but I think its publication might be premature given that, for example, the work on unique and aggregated nicknames is still in progress in the WG -- even if that work is stable, there's still a (maybe small) probability of this document falling out of sync.

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

The IANA Services Operator has reviewed draft-ietf-trill-rbridge-multilevel-05.txt, 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.

Thank you,

Sabrina Tanamal
IANA Services Specialist
PTI

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC: shares@ndzh.com, trill-chairs@ietf.org, trill@ietf.org, draft-ietf-trill-rbridge-multilevel@ietf.org, akatlas@gmail.com
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Alternatives for Multilevel TRILL (Transparent Interconnection of Lots of Links)) to Informational RFC


The IESG has received a request from the Transparent Interconnection of Lots
of Links WG (trill) to consider the following document: - 'Alternatives for
Multilevel TRILL (Transparent Interconnection of Lots
  of Links)'
  as Informational RFC

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 2017-06-28. 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


  Although TRILL is based on IS-IS, which supports multilevel unicast
  routing, extending TRILL to multiple levels has challenges that are
  not addressed by the already-existing capabilities of IS-IS.  One
  issue is with the handling of multi-destination packet distribution
  trees. Other issues are with TRILL switch nicknames. How are such
  nicknames allocated across a multilevel TRILL network? Do nicknames
  need to be unique across an entire multilevel TRILL network or can
  they merely be unique within each multilevel area?

  This informational document enumerates and examines alternatives
  based on a number of factors including backward compatibility,
  simplicity, and scalability and makes recommendations in some cases.







The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-trill-rbridge-multilevel/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-trill-rbridge-multilevel/ballot/

The following IPR Declarations may be related to this I-D:

  https://datatracker.ietf.org/ipr/1579/
  https://datatracker.ietf.org/ipr/1813/

Format reference:  RFC 4858, this is the current template for the Document (2/24/2012)

Status of shepherd's report:  Submitted to IESG for review.

==================

(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?

Type: Informational.
Why is it the right type:  Describes the reason why the WG is allowing a choice of
This informational document suggests allowing a choice of approach to
allow multiple-levels between:
a) unique nicknames - giving a unique nickname to all TRILL switches in
  L1/L2 areas, and having L1/L2 border switch advertise to the area which is available at
  each level or having address space split between area/node-nickname
b) aggregated nicknames - hiding nicknames used in each area and having
border TRILL switches rewrite nicknames on ingress/egress TRILL packets.

Understanding these choices is useful to deployments  - so this informational
draft is useful to users, vendors, and researchers.

(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
  Extending TRILL to multiple levels has challenges that are not
  addressed by the already-existing capability of IS-IS to have
  multiple levels.  One issue is with the handling of multi-destination
  packet distribution trees. Another issue is with TRILL switch
  nicknames.  There have been two proposed approaches.  One approach,
  which we refer to as the "unique nickname" approach, gives unique
  nicknames to all the TRILL switches in the multilevel campus, either
  by having the Level-1/Level-2 border TRILL switches advertise which
  nicknames are not available for assignment in the area, or by
  partitioning the 16-bit nickname into an "area" field and a "nickname
  inside the area" field.  The other approach, which we refer to as the
  "aggregated nickname" approach, involves hiding the nicknames within
  areas, allowing nicknames to be reused in different areas, by having
  the border TRILL switches rewrite the nickname fields when entering
  or leaving an area. Each of those approaches has advantages and
  disadvantages.

  This informational document suggests allowing a choice of approach in
  each area. This allows the simplicity of the unique nickname approach
  in installations in which there is no danger of running out of
  nicknames and allows the complexity of hiding the nicknames in an
  area to be phased into larger installations on a per-area basis.


Working Group Summary

  WG has worked on these solutions for 2+ years. 
  The WG consensus had no objections, and support of all key players with comments.

  WG LC:
  https://www.ietf.org/mail-archive/web/trill/current/msg07079.html

Document Quality

Protocol extension has no implementation of this code.
Huawei plans to implement this function.

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?

  RTG-DIR review:
    RTG-DIR Reviewer: Stig Venaas
    https://www.ietf.org/mail-archive/web/trill/current/msg07478.html

No other reviews required.

Personnel
  Document shepherd: Susan Hares
  Responsible AD: Alia Atlas
  RTG-DIR reviewer: Stig Venaas

(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.

Shepherd review:
(first review)
https://www.ietf.org/mail-archive/web/trill/current/msg07254.html
(-03.txt review)
To be added

Nits run:
No errors except:
  == There are 1 instance of lines with non-RFC6890-compliant IPv4 addresses
    in the document.  If these are example addresses, they should be changed.

This is an error in nits program.  The addresses are not IPv4 addresses.

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

No.

(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.

No wider reviews needed for informational.

(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 WG has discussed those issues and
has indicated that it still wishes to advance the document, detail those
concerns here.

No additional concerns.

(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.

Mingui Zhang:
https://www.ietf.org/mail-archive/web/trill/current/msg07081.html
Radia Perlman
https://www.ietf.org/mail-archive/web/trill/current/msg07091.html
Donald Eastlake:
https://www.ietf.org/mail-archive/web/trill/current/msg07093.html
Anoop Ghanwani
https://www.ietf.org/mail-archive/web/trill/current/msg07098.html

Hongjun Zhai - 
https://www.ietf.org/mail-archive/web/trill/current/msg07516.html

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

yes
https://datatracker.ietf.org/ipr/search/?submit=draft&id=draft-ietf-trill-rbridge-multilevel
https://datatracker.ietf.org/ipr/1813/
https://datatracker.ietf.org/ipr/1579/

The IPR disclosures have existed since the draft was adopted with the IPR disclosed in 2012.

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

The discussions on multi-level occurred over 3 years - so the lack of contention is the result of lots discussions at IETF session on multi-level prior to drafts.

(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 appeals pending.

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

Nits run:
No errors except:
  == There are 1 instance of lines with non-RFC6890-compliant IPv4 addresses
    in the document.  If these are example addresses, they should be changed.

This is an error in nits program.  The addresses are not IPv4 addresses.

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

Informational document that is useful to users, vendors, TRILL WG, and
any researchers examining the TRILL work.  No MIB, yang, media, or URI reviews.

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

Normative - Ok.
Informative - checking on four drafts

  1) [DraftAggregated] - Bhargav Bhikkaji, Balaji Venkat Venkataswami,
        Narayana Perumal Swamy, "Connecting Disparate Data
        Center/PBB/Campus TRILL sites using BGP", draft-balaji-trill-over-ip-multi-level, Work In Progress.

This draft is individual draft, but it is a current work.  The AD should consider the status.

All other informative references are TRILL WG drafts.

(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.

No.

(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 WG considers it unnecessary.

No.  - it is informational only.

(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 IANA related work.  Just an informational draft.

(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.

Not applicable.

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

Not applicable.