Operational Management of Loop-Free Alternates
draft-ietf-rtgwg-lfa-manageability-11

[Ballot comment]
Ron Bonica's Opsdir review.

Folks,

I have reviewed this document as part of the Operational directorate's ongoing effort to review all IETF documents being processed by the IESG.  These comments were written with the intent of improving the operational aspects of the IETF drafts. Comments that are not addressed in last call may be included in AD reviews during the IESG review.  Document editors and WG chairs should treat these comments just like any other last call comments.

This document is on the Standards Track. It provides operational feedback on LFA, highlights some limitations, and proposes a set of refinements to address those limitations.  It also proposes required management specifications.

The document is well-written and nearly ready for publication.

Major Issues
----------------
None

Minor Issues
---------------
- Please run this document through the NIT checker and address the NITS

- I am not sure how the sitting IESG feels about the use of lowercase "must", "should" and "may". You may want to check this before the IESG review.


Ron Bonica

---

example that I would cite as good to all caps

6.1
...


  o  Per prefixes: prefix protection SHOULD have a better priority
      compared to interface protection.  This means that if a specific
      prefix must be protected due to a configuration request, LFA must
      be computed and installed for this prefix even if the primary
      outgoing interface is not configured for protection.

LFA MUST

since it's a requirement

in most other cases I see a lower cast must what is being described is the logic that draws you to a conclusion, and those are ok.

[Ballot comment]
Similar to others, I find the readability/English poor. I think it will be too much for the RFC Editor and the RFC Editor will not catch some of these errors e.g.:
- 6.2.4.1 SRLG "preference system"
- 6.2.4.2 "Link coloring is a powerful system"
I would say (similar to Alvaro's comment on "alert system"), it's not a "system". A better wording would be "technique" or "method". Agree with others, a proof reading pass is really needed.

[Ballot comment]
I've got nothing that rises to the level of a discuss, but I do have a few comments:

*** Substantive Comments: ***

-- section 4, last paragraph:

This is an odd thing to make normative. It seems more a question of business and ecosystem decisions.

-- 6.2.4.2:

Can you explain the "color" metaphor, or reference an explanation?

-- 8:

The entirety of the security considerations are of the form of "No new considerations compared to [RFC5286]". Please offer supporting arguments for that. For example, a high-level description of the nature of the changes, new behaviors, or clarifications introduced in this draft, and how those do or do not impact the security considerations.


*** Editorial Comments: ***

-- General:

There are pervasive grammatical errors, especially incorrect use of singular and plural forms, missing articles, and incorrect use of commas. The RFC editor will fix these, but you could save them quite a bit of work by making another proofreading pass.

Also, throughout the draft, there are lists of examples in the form of ":A,B,C...". I suggest using the form "A,B,C etc.", or even better "For example , A, B, and C" or "e.g., A, B, and C"

-- section 2, first bullet:

Last sentence is a fragment.

-- 3.1, last paragraph:

This seems to say that, in addition to the technical issues mentioned here, service providers simply might not like it. Is that really what you mean to say?

-- 4, last bullet:

Missing "to" . Otherwise, this renders to "... may be able monitor constantly..."

-- 5, first paragraph: "As all FRR mechanism, ..."

I think there's one or more missing words. Do you mean "As [in/for] all other FRR mechanisms, ..."?

"Depending of the hardware..."

s/of/on

'... compared to the amount of destinations in RIB."

I suggest " ... compared to the number of destinations in the RIB."

-- 2nd paragraph " ... permit to compute ... "

"Permit" needs a direct object. That is "... permits [something] to compute...". What is the something?

(Note: This construction appears several times)

-- 6.1, first paragraph: "The granularity of LFA activation should be controlled ..."

-- 6.1, last bullet in first list: "... SHOULD have a better priority ... "
s/better/higher

-- 6.2, item 3 in the numbered list: "... an implementation SHOULD pick only one based on its own
      decision, as a default behavior."

A "default behavior" implies that people might make non-default choices. I suggest striking the phrase", as a default behavior".



I'm not sure what that means.

-- 2nd paragraph: " ... following criteria:"

I suggest s/criteria/granularities

(Note: I see quite a bit of the use of the word "criteria" when I think you mean something else. )

-- 6.2.3:

What does "enhanced criteria" mean? Also the word "Downstreamness" seems a bit of a stretch, but if the RFC editor lets that get by then more power to you :-)

-- 6.2.4.1:
Please expand SRLG on first mention.

-- 6.2.5.4: 5th paragraph "... it is needed to limit..."

perhaps "... implementations need to limit..."

-- 9 and 10:

Section 9 is out of place (should probably go right before references), and 10 is empty.

[Ballot comment]
I've got nothing that rises to the level of a discuss, but I do have a few comments:

*** Substantive Comments: ***

-- section 4, last paragraph:

This is an odd thing to make normative. It seems more a question of business and ecosystem decisions.

-- 6.2.4.2:

Can you explain the "color" metaphor, or reference an explanation?

-- 8:

The entirety of the security considerations are of the form of "No new considerations compared to [RFC5286]". Please offer supporting arguments for that. For example, a high-level description of the nature of the changes, new behaviors, or clarifications introduced in this draft, and how those do or do not impact the security considerations.
*** Editorial Comments: ***

-- General:

There are pervasive grammatical errors, especially incorrect use of singular and plural forms, missing articles, and incorrect use of commas. The RFC editor will fix these, but you could save them quite a bit of work by making another proofreading pass.

Also, throughout the draft, there are lists of examples in the form of ":A,B,C...". I suggest using the form "A,B,C etc.", or even better "For example , A, B, and C" or "e.g., A, B, and C"

-- section 2, first bullet:

Last sentence is a fragment.

-- 3.1, last paragraph:

This seems to say that, in addition to the technical issues mentioned here, service providers simply might not like it. Is that really what you mean to say?

-- 4, last bullet:

Missing "to" . Otherwise, this renders to "... may be able monitor constantly..."

-- 5, first paragraph: "As all FRR mechanism, ..."

I think there's one or more missing words. Do you mean "As [in/for] all other FRR mechanisms, ..."?

"Depending of the hardware..."

s/of/on

'... compared to the amount of destinations in RIB."

I suggest " ... compared to the number of destinations in the RIB."

-- 2nd paragraph " ... permit to compute ... "

"Permit" needs a direct object. That is "... permits [something] to compute...". What is the something?

(Note: This construction appears several times)

-- 6.1, first paragraph: "The granularity of LFA activation should be controlled ..."

-- 6.1, last bullet in first list: "... SHOULD have a better priority ... "
s/better/higher

-- 6.2, item 3 in the numbered list: "... an implementation SHOULD pick only one based on its own
      decision, as a default behavior."

A "default behavior" implies that people might make non-default choices. I suggest striking the phrase", as a default behavior".



I'm not sure what that means.

-- 2nd paragraph: " ... following criteria:"

I suggest s/criteria/granularities

(Note: I see quite a bit of the use of the word "criteria" when I think you mean something else. )

-- 6.2.3:

What does "enhanced criteria" mean? Also the word "Downstreamness" seems a bit of a stretch, but if the RFC editor lets that get by then more power to you :-)

-- 6.2.4.1:
Please expand SRLG on first mention.

-- 6.2.5.4: 5th paragraph "... it is needed to limit..."

perhaps "... implementations need to limit..."

-- 9 and 10:

Section 9 is out of place (should probably go right before references), and 10 is empty.

[Ballot comment]
I only have a few editorial things to add:

-- Section 4 --

  Implementers SHOULD document their LFA selection algorithms (default
  and tuning options) in order to leave possibility for 3rd party
  modules to model these policy-LFA expressions.

I'm not going to whine about this *too* much, but I don't see this as an appropriate use of 2119 key words.  I'd be happier if it were changed to not be a 2119 word.  That said, there's no need for discussion.  Do as you think best.

-- Section 6.2 --

  3.  If the defined policy does not permit to determine a unique best
      LFA,

The wording here is really awkward English.  The verb "permit" needs a direct object here, as in "does not permit  to determine ."  You can't just omit the .  The easiest fix is to change "to determine" to "the determination of".  (I would also use "allow" rather than "permit", but that's just a personal wording preference.)

-- Section 6.2.4.1 --

  When SRLG protection is computed, and implementation SHOULD permit to

Same problem here as in 6.2, above, but because of the list the fix isn't as easy.  First, "and" should be "an".  Second, the fix should probably be like this:

NEW
  When SRLG protection is computed, an implementation SHOULD permit the
  following:

  o  Exclusion of alternates violating SRLG.

  o  Maintenance of a preference system between alternates based on
      SRLG violations. [...etc...]
END

In the first sub-bullet, "Preference based on number of violation," both instances of "violation" should be "violations".

-- Section 7.3 --

  o  MUST be able to display, for every prefixes, the primary next hop
      as well as the alternate next hop information.

"prefixes" should be "prefix".

-- Section 7.4 --
When you say "provide an alert system" here, I think you mean "provide an alert", or, perhaps better, "trigger an alert" or "generate an alert".  Presumably, in order to do that, an alert system has to be available.  But the point here is that you saying when specific alerts should be triggered/generated.

[Ballot comment]
1. The abstract mentions a lot of things that this document covers: “provides operational feedback on LFA, highlights some limitations, and proposes a set of refinements to address those limitations.  It also proposes required management specifications.”  The Introduction presents a quick guide to what some sections cover (good idea!), but not all sections are mentioned there.

It would be nice to cover all the sections in the “document map” in the introduction.


2. In section 3.1 it may not be clear to all readers why P4 is not an LFA for P8.  In all the other cases there is an explicit statement (a sentence or two) that explains and clarifies.


3. In Section 6.2.4.2 the document talks about signaling color information, it includes a set of requirements..and it reads “How signaling is done is out of scope of the document”, but then you go on and point to a specific solution.  Even if there might be a high certainty that the solution you point at is moving on in the process, is good, should be used, etc..  I think this document would be better served by just defining the requirements (specially if you’re pointing at the solution as out of scope).  You do the same in 6.2.4.4.


4. The IS-IS overload bit is mentioned in several places as important to consider.  Are there similar considerations related to the use of the OSPF MaxLinkMetric or the R-bit?  If so, please include them..if not, please explain why in the document.  [BTW, there is no reference pointing to the OL bit.]

The updated version addresses my AD review concerns.  The improvements aren't technical changes, but since they
are a bit more than merely editorial, I have asked RTGWG to provide some quick reviews and I intend to hold the draft
in AD followup until June 30, unless I hear back positively from RTGWG.

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

IANA has reviewed draft-ietf-rtgwg-lfa-manageability-08, which is currently in Last Call, and has the following comments:

We understand that, upon approval of this document, there are no IANA Actions that need completion.

While it is helpful for the IANA Considerations section of the document to remain in place upon publication, if the authors prefer to remove it, IANA doesn't object.

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

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Operational management of Loop Free Alternates) to Proposed Standard


The IESG has received a request from the Routing Area Working Group WG
(rtgwg) to consider the following document:
- 'Operational management of Loop Free Alternates'
  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 2015-06-18. 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


  Loop Free Alternates (LFA), as defined in RFC 5286 is an IP Fast
  ReRoute (IP FRR) mechanism enabling traffic protection for IP traffic
  (and MPLS LDP traffic by extension).  Following first deployment
  experiences, this document provides operational feedback on LFA,
  highlights some limitations, and proposes a set of refinements to
  address those limitations.  It also proposes required management
  specifications.

  This proposal is also applicable to remote LFA solution.





The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-rtgwg-lfa-manageability/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-rtgwg-lfa-manageability/ballot/


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

  https://datatracker.ietf.org/ipr/2490/
  https://datatracker.ietf.org/ipr/2196/

(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?

  The Intended Status is 'Proposed Standard'. 
  The type of RFC is properly indicated in the title page header.
  This draft provides operational feedback on LFA, RFC286, (also Standards Track) document.

(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

  This draft provides operational feedback on LFA (RFC5286), highlights some limitations,
  and proposes a set of refinements to address those limitations. 
  It also proposes required management specifications.

Working Group Summary

  This draft has been thoroughly discussed in the WG, very good feedback had been provided by SP and vendor community.
  The draft adoption and progress had received full support from the WG.
  All comments have been addressed.  The draft is ready for publication.

Document Quality

  There are existing implementations and multiple vendors have shown significant interest in the topic. 

Personnel

  Jeff Tantsura is the Document Shepherd.
  Alia Atlas is the Responsible Area Director.

(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 draft has been thoroughly reviewed by the Shepherd.
  All comments have been addressed.  The draft is ready for publication.

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

  No concerns.

(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.

  N/A

(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.

  N/A

(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.  Every author has confirmed.

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

  Yes.  The authors have been asked (and they answered) on the WG
  list about IPR at every step of the process.  There haven't been
  any concerns raised on the list.

(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 draft adoption and progress had received full support from the WG,
  As mentioned above, significant discussion (including several vendors and operators)
  has taken place on the list.

(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.

(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.

  No nits.

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

  N/A

(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.

  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.

  The state of other documents remains unchanged.

(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).

  This draft has no action for IANA.

(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 the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.

  N/A