Application-Aware Targeted LDP
draft-ietf-mpls-app-aware-tldp-09

[Ballot comment]
(I cleared my discuss. Alexey pointed out that the registration policies for unassigned ranges are explicitly mentioned in the table itself. Apologies, I missed that.)

-General:  When you use the word "application", is a person skilled in MPLS automatically going to think in terms of the sort of "applications" listed here? If not, it would be good to have a paragraph early in the introduction that describes what you mean by "applications". As an application-layer person, I tend to think of it in terms of application-layer applications. Am I correct to assume that it would not make sense to register, for example, HTTP in the the LDP Targeted Application Identifier registry?

- 1.1: I noticed a number instances of at least "may" in lower case. If your intent is that lower case words not be treated as keywords, please consider using the new boilerplate from RFC 8174

Nits:

-1, first paragraph: "LDP uses extended discovery mechanism..."
Missing article before "discovery".

-2.2, paragraph 4 and 5, "... a maximum value, as 0xffff.": should "as" be "such as"?

-2.2, paragraphs 6 and 7: the "it" in the opening sentence of each paragraph has an unclear antecedent.

[Ballot comment]
Close to a DISCUSS, but in the end a COMMENT, assuming I don't know enough about tLDP.
Let's have a discussion regardless.

  This document
  defines a mechanism to advertise and negotiate Targeted Applications
  Capability (TAC) during LDP session initialization.

...
  This document proposes and describes a solution to advertise Targeted
  Application Capability (TAC), consisting of a targeted application
  list, during initialization of a tLDP session.

...
  An LSR MAY advertise that it is capable to negotiate a targeted LDP
  application list over a tLDP session by using the Capability
  Advertisement as defined in [RFC5561] and encoded as follows:

...
  At tLDP session establishment time, a LSR MAY include a new
  capability TLV, TAC TLV, as an optional TLV in the LDP Initialization
  message.


Reading the doc., I've been wondering for many pages now. Do we speak negotation ...
From the initiating LSR: these are the Targeted Application (Identifier(s)) for which I would like to initializate a tLDP
Answer from the responding LSR: yes, possible. No, not possible
Question: is the tLDP session established.

From the initiating LSR: from this list, tell me which Targeted Application (Identifiers) you support
Answer from the responding LSR: here are the Targeted Application (Identifiers) I support

From the receiving LSR: here are the Targeted Application (Identifiers) I support

Throughout the doc, clarify if the LSR is the initiating or receiving party.
As a starting point, this text should be updated:

      At tLDP session establishment time, a LSR MAY include a new
      capability TLV, TAC TLV, as an optional TLV in the LDP Initialization
      message.

LSR => initiating LSR.

Oh, wait, then I've been confused with: "If both the peers advertise TAC TLV,"
So both can start the negotiation?

Then you speak about "the responding LSR playing the active role in LDP session"
So it's not about initiating/responding LSR any longer.

A small diagram with arrows, at least for the most common case, would go a long way.

[Ballot comment]
Please expand the following acronyms upon first use and in the title;
see https://www.rfc-editor.org/materials/abbrev.expansion.txt for guidance.

- LSR - Label Switching Router
- mLDP - Multipoint LDP
- PQ - Unknown
- TAI - Unknown
- RSVP-TE - RSVP - Traffic Engineering
- P2MP - Point-to-Multipoint
- PW - pseudowire
- P2P-PW - Peer-to-peer Psuedowire (presumably?)
- MP2MP - Multipoint-to-Multipoint
- HSMP - Unknown
- LSP - Label Switched Path
- MP2P - Unknown (should this be P2MP?)
- MPT - Unknown

[Ballot comment]
Document: draft-ietf-mpls-app-aware-tldp-00.txt

  LDP can use the extended discovery mechanism to establish a tLDP
  adjacency and subsequent session as described in [RFC5036]. An LSR

Please expand LDP and tLDP on first use. Also, I don't see tLDP in
RFC 5037 despite the citation


S 2.1.
      A Targeted Applications Capability data consists of none, one
      or more 32 bit Targeted Application Elements. Its encoding is
      as follows:

This is ungrammatical. Is it intended to say "zero or more"?

S 2.2.
  If the receiver LSR does not receive the TAC in the Initialization
  message or it does not understand the TAC TLV, the TAC negotiation
  MUST be considered unsuccessful and the session establishment MUST
  proceed as per [RFC5036]. On the receipt of a valid TAC TLV, an LSR
  MUST generate its own TAC TLV with TAEs consisting of unique TA-Ids
  that it supports over the tLDP session. If there is at least one TAE
  common between the TAC TLV it has received and its own, the session
  MUST proceed to establishment as per [RFC5036]. If not, A LSR MUST
  send a 'Session Rejected/Targeted Application Capability Mis-Match'
  Notification message to the peer and close the session. The
  initiating LSR SHOULD tear down the corresponding tLDP adjacency
  after send or receipt of a 'Session Rejected/Targeted Application
  Capability Mis-Match' Notification message to or from the responding
  LSR respectively.

This seems like odd semantic: if I don't understand the TLV, I continue
with session establishment, but if I understand it but there's no overlap
I close the session?


  instance, suppose a initiating LSR advertises A, B and C as TA-Ids.
  Further, suppose the responding LSR advertises C, D and E as TA-Ids.
  Than the negotiated TA-Id, as per both the LSRs is C. In the second
  instance, suppose a initiating LSR advertises A, B and C as TA-Ids
  and the responding LSR, which acts as a passive LSR, advertises all
  the applications - A, B, C, D and E that it supports over this
  session. Than the negotiated targeted application as per both the

Should this say "applications"? It seems like you're just computing
intersection.

  If the Targeted Application Capability and Dynamic Capability, as
  described in [RFC5561], are negotiated during session initialization,
  TAC MAY be re-negotiated after session establishment by sending an
  updated TAC TLV in LDP Capability message. The updated TAC TLV
  carries TA-Ids with incremental update only. The updated TLV MUST
  consist of one or more TAEs with E-bit set or E-bit off to advertise
  or withdraw the new and old application respectively. This may lead
  to advertisements or withdrawals of certain types of FEC-Label
  bindings over the session or tear down of the tLDP adjacency and
  subsequently the session. 

So, advertisements are cumulative? If I advertise A, B and then C,
that means I do A, B, C?

[Ballot comment]
1: Does this document really need 6 front page authors?

2: The shepherd writeup says: "We are aware of several intentions to implement this secification. An implementation poll has been sent to the working group and as further information is received, the write-up will be updated." -- was any further info received?

3: The shepherd writeup also says: "There is one small issue that I'm currently clearing with IANA." -- is this the value of the status code E bit? Or some other issue?

Nits:
1: There are are a number of unexpanded acronyms -- e.g: LSP is no "well known" - https://www.rfc-editor.org/materials/abbrev.expansion.txt

2: Sec 1  Introduction
"LDP uses extended discovery mechanism to establish..." - "LDP uses *the* extended discovery mechanism" (or discovery *mechanisms*)

3: Sec 1  Introduction
"An LSR initiates extended discovery... " - "A LSR..." ("An Label Switch" wouldn't make much sense)

4: Sec 1  Introduction
"In addition, since the session is initiated and established after adjacency formation, the responding LSR has no targeted applications information to choose the targeted application" - "has no targeted applications information available to choose which targeted application".

5: Sec 1  Introduction
"Also, targeted LDP application is mapped .." - "Also, the targeted LDP application is mapped"

6: Sec 1.2 Terminology
"This document uses terminology discussed in [RFC7473] along with others defined in this document." feels clumsy. How about:
"In addition to the terminology defined in [RFC7473], this document uses the following terms: "

7: Sec 2.1 Encoding
"An LSR MAY advertise that it is capable to negotiate a targeted LDP ..." - "An LSR MAY advertise that it is capable of negotiating a targeted LDP ..."

[Ballot discuss]
This should be easy to fix, but needs to be fixed before the draft progresses:

Section 7 establishes a new IANA registry under the Label Distribution Protocol (LDP) Parameters page. Unless I missed something (which happens) it doesn't specify the registration policy as required by BCP26. Please see RFC 5226 section 4.1 for details.

[Ballot comment]
-General:  When you use the word "application", is a person skilled in MPLS automatically going to think in terms of the sort of "applications" listed here? If not, it would be good to have a paragraph early in the introduction that describes what you mean by "applications". As an application-layer person, I tend to think of it in terms of application-layer applications. Am I correct to assume that it would not make sense to register, for example, HTTP in the the LDP Targeted Application Identifier registry?

- 1.1: I noticed a number instances of at least "may" in lower case. If your intent is that lower case words not be treated as keywords, please consider using the new boilerplate from RFC 8174

Nits:

-1, first paragraph: "LDP uses extended discovery mechanism..."
Missing article before "discovery".

-2.2, paragraph 4 and 5, "... a maximum value, as 0xffff.": should "as" be "such as"?

-2.2, paragraphs 6 and 7: the "it" in the opening sentence of each paragraph has an unclear antecedent.

[Ballot comment]
1. A pointer to the applications mentioned in the Introduction would be nice (FEC 128, rLFA, etc.) in first mention.

2. In Section 2.2 (Procedures):

2.1. "The TAC TLV's Capability data MAY consists of none, one or more TAE each pertaining to a unique TA-Id that a LSR supports over the session." If there is no TAE, how can it be related to a TA-Id?  Also, I think that the "MAY" in this case is just stating a fact, so it should be "may".

2.2. "For instance, if the tLDP session is established for BGP auto discovered pseudowire, only FEC 129 label bindings MUST be distributed over the session."  That "MUST" shouldn't be in caps because it is part of an example.

2.3. TAI is used instead of TA-Id twice at the end of the section.

[Ballot comment]
I have a small list of issues that I think you should look at:

LSR -- needs expansion in the Abstract, as it is not an abbreviation recognized by RFC Editor.

In 2.2

  If the receiver LSR does not receive the TAC TLV in the Initialization message
  or it does not understand  the TAC TLV, the TAC negotiation MUST be considered
  unsuccessful and the session establishment MUST proceed as per [RFC5036].

Firstly, you can't have requirements on any implementation that doesn't support this specification. Secondly, the last MUST is already the default. So I think use of RFC 2119 lange here is not appropriate, you should just use "is considered" and "proceeds".

The following text:

If it sets the session setup retry interval to maximum, the session MAY stay in a non-existent state. When this LSR detects a change in the responding LSR configuration or its own configuration pertaining to TAC TLV, it MUST clear the session setup back off delay associated with the session in order to re-attempt the session establishment.

is repeated twice in the same section.

What is "TAI"?

In 5.2: the section is titled "Use Cases", so I didn't expect any normative RFC 2119 language in there. Some MAY seem not to be specifying implementation choices, so they should be "may".

[Ballot comment]
nits regarding use of normative language:

1) sec 2.2.: „Therefore, if
  the intersection of the sets of received and sent TA-Id is null, then
  LSR MUST send 'Session Rejected/Targeted Application Capability Mis-
  Match' Notification message to the initiating LSR and close the
  session.“
Probably no need to make this normative MUST again in the example text
-> s/MUST send/sends/

2) Similar the use of normative language in the use case section (5) does not seem to be appropriate, or at least not consistent. Maybe just convert all upper cases MAYs to lower case in that section.

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

The IANA Services Operator has completed its review of draft-ietf-mpls-app-aware-tldp-08.txt. If any part of this review is inaccurate, please let us know.

The IANA Services Operator has a question about one of the actions requested in the IANA Considerations section of this document.

The IANA Services Operator understands that, upon approval of this document, there are three actions which we must complete.

First, in the TLV Type Name Space registry located on the Label Distribution Protocol (LDP) Parameters registry page at:

https://www.iana.org/assignments/ldp-namespaces/

a single, new entry is to be registered as follows:

Value: [ TBD-at-registration ]
Description: Targeted Applications capability
Reference: [ RFC-to-be ]

We note that the authors have requested that the value assigned by the lowest available value after 0x050B.

Second, in the Status Code Name Space registry also located on the Label Distribution Protocol (LDP) Parameters registry page at:

https://www.iana.org/assignments/ldp-namespaces/

a single, new entry is to be registered as follows:

Range/Value: [ TBD-at-registration ]
E:
Description: Session Rejected/Targeted Application Capability Mis-Match
Reference: [ RFC-to-be ]

IANA Question -> What is the value of E for this new status code?

Third, a new registry is to be created called the LDP Targeted Application Identifier registry. The new registry will be located on the Label Distribution Protocol (LDP) Parameters registry page at:

https://www.iana.org/assignments/ldp-namespaces/

There are initial registrations in the new registry and the rules for maintenance in the registry are as follows:

Value Description Reference
-------- ------------------------- ---------------
0x0000 Reserved [ RFC-to-be ]
0x0001 LDPv4 Tunneling [ RFC-to-be ]
0x0002 LDPv6 Tunneling [ RFC-to-be ]
0x0003 mLDP Tunneling [ RFC-to-be ]
0x0004 LDPv4 Remote LFA [ RFC-to-be ]
0x0005 LDPv6 Remote LFA [ RFC-to-be ]
0x0006 LDP FEC 128 PW [ RFC-to-be ]
0x0007 LDP FEC 129 PW [ RFC-to-be ]
0x0008 LDP Session Protection [ RFC-to-be ]
0x0009 LDP ICCP [ RFC-to-be ]
0x000A LDP P2MP PW [ RFC-to-be ]
0x000B mLDP Node Protection [ RFC-to-be ]
0x000C LDPv4 Intra-area FECs [ RFC-to-be ]
0x000D LDPv6 Intra-area FECs [ RFC-to-be ]
0x0001 - 0x1FFF Available for assignment
by IETF Review
0x2000 - 0F7FF Available for assignment
as first come first served
0xF800 - 0xFBFF Available for private use
0xFC00 - 0xFFFE Available for experimental use
0xFFFF Reserved [ RFC-to-be ]

The IANA Services Operator understands that these three actions are the only ones 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 only to confirm what actions will be performed.


Thank you,

Sabrina Tanamal
IANA Services Specialist
PTI

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC: mpls@ietf.org, draft-ietf-mpls-app-aware-tldp@ietf.org, mpls-chairs@ietf.org, db3546@att.com, loa@pi.nu
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Application-aware Targeted LDP) to Proposed Standard


The IESG has received a request from the Multiprotocol Label Switching WG
(mpls) to consider the following document:
- 'Application-aware Targeted LDP'
  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 2017-06-09. 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


  Recent targeted LDP (tLDP) applications such as remote loop-free
  alternate (LFA) and BGP auto discovered pseudowire may automatically
  establish a tLDP session to any LSR in a network.  The initiating LSR
  has information about the targeted applications to administratively
  control initiation of the session. However, the responding LSR has no
  such information to control acceptance of this session. This document
  defines a mechanism to advertise and negotiate Targeted Applications
  Capability (TAC) during LDP session initialization.  As the
  responding LSR becomes aware of targeted applications, it may
  establish a limited number of tLDP sessions for certain applications.
  In addition, each targeted application is mapped to LDP Forwarding
  Equivalence Class (FEC) Elements to advertise only necessary LDP FEC-
  label bindings over the session. This document updates RFC 7473 for
  enabling advertisement of LDP FEC-label bindings over the session.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-mpls-app-aware-tldp/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-mpls-app-aware-tldp/ballot/

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

  https://datatracker.ietf.org/ipr/2507/
  https://datatracker.ietf.org/ipr/2796/

As required by RFC 4858, this is the current template for the Document
Shepherd Write-Up.

  The MPLS WG requests that

                    Application-aware Targeted LDP
                  draft-ietf-mpls-app-aware-tldp

  is published as an RFC on the Standards Track (PS)

(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 type of document should be Proposed Standard - the title page
  says:
  Intended Status: Proposed Standard.

  The document specifies protocol, protocl elements and procedurtes,
  so it should be publsihed as a 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

  Some tLDP applications e.g. remote loop-free alternate (LFA) and
  BGP auto discovered pseudowires may establish a tLDP session to any
  LSR in a network. The LSR that initializes such a session has
  enough information to administratively control initiation of the
  session. The targetted LSR normally does not have the information
  necessary to control acceptance of the requested session. This
  document defines a mechanism to advertise and negotiate Targeted
  Applications Capability (TAC) during LDP session initialization.
  The targetted LSR is made aware of targeted applications through
  the TAC information. When this happens it can establish a limited
  number of tLDP sessions for certain applications.
  In addition, each targeted application is mapped to LDP Forwarding
  Equivalence Class (FEC) Elements to advertise only necessary LDP
  FEC-label bindings over the session.

Working Group Summary

  Was there anything in WG process that is worth noting? For
  example, was there controversy about particular points or
  were there decisions where the consensus was particularly
  rough?

  The wg process for this document has been fairly normal, and
  the working agree that this is a necessary extension to LDP
  for some applications. Discussion has been targetted on resolving
  a small number of outstanding issues. The consensus in the working
  are good.

Document Quality

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

  We are aware of several intentions to implement this secification.
  An implementation poll has been sent to the working group and as
  further information is received, the write-up will be updated.
  No expert review outside the working group is necessary.

Personnel

  Loa Andersson is the Document Shepherd.
  Deborah Brungard 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 document shepherd has reviewd the document fully three times:
  - when the -00 individual version was posted
  - as part of adopting the document as a working group document
  - as part of preparing the document for wglc
  - a scoped review (including IANA section) was done as part of
    preparing the publication request.

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

  No such concerns, the document has been reviewed by the working
  group (at wgap and wglc), it has been reviewed by the mpls-rt and
  wg chair/shepherd. Each of the reviews have resulted on comments
  that depending on the nature been addressed on (technical) or
  off (editorial) the list



(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 such conserns.

(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 such 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.

  All the authors have stated on the working group list that they
  are not aware of any IPRs other than those that has been disclosed
  through the IETF process.

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

  The IETF IPR pages lists two IPRs disclosed against this dcoument,
  in reality it is only IPR that has been updated as the dicument
  changed file-name when accepted as a wg doc.
  The MPLS WG makes the working group aware of existing IPRs at
  working group adoption and working group last call. We ask if there
  are any concerns about the IPR, i.e. silence is interpreted as
  accepting the conditions in the IPR disclosure.

(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? 

  It is very solid, this is something that is needed in MPLS networks
  using LDP. 

(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 such threats!

(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.

  The document passes nits tool clean.

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

  No such reviews neweded.

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

  Yes, the references are correctly split into normative and
  informative refernces.

(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?

  All the normative refrences are to existing standard tracks RFCs.

(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 downwad references.

(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.

  There will be no changes of status for any RFCs when this document
  is published.

(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).

  The Document Shepherd has reviewed the IANA section several times,
  it is clear and well-written.
  There is one small issue that I'm currently clearing with 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.

  No such registries.

(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.

  No other automated reviewa than nits tool is necessary.