RSVP-TE Extensions for Associated Bidirectional Label Switched Paths (LSPs)
draft-ietf-teas-mpls-tp-rsvpte-ext-associated-lsp-07

[Ballot comment]
The term "reverse unidirectional LSPs" breaks my head as you really mean something like bi-directional bundled LSPs. But anyhow, that might be just me.

[Ballot comment]

I don't have any specific threat to offer, but I have to say
this sets my antennae jangling a bit from a security
perspective. If you let someone loose on an ingress node here
who could setup these bidirectional associations, I'd imagine
they could generate fun and profit, would that be fair?  Has
anyone tried to play the attacker/red-team here to see if
they can find any issues with this? Could I probe from the
ingress node and figure out what other LSPs exist at an
egress node, and they try take those over?

As another nit, I see we say here "introduce no additional"
but see RFC6780, which says "no new security considerations
are introduced" and "there are no new risks" and we all point
back to RFC5920. (Sorry for the whine, that "nothing new
here" thing grates when one sees it so often;-)

I guess I basically wish I shared your confidence. And while
I don't, I also don't know enough about MPLS to point out
anything that'd justify trying to block this.

Email to authors
=====
Hi,

Last call completed on this document, but I think you have a little work to do.

At the least you need to resolve the remaining issue that Lou took to the mailing list.

Can you also please check to see whether there were any directorate reviews of last call comments and address them as necessary.

As soon as you can produce a new revision or close the outstanding issues I will advance the document.

Thanks for the work,
Adrian

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (RSVP-TE Extensions for Associated Bidirectional LSPs) to Proposed Standard


The IESG has received a request from the Traffic Engineering Architecture
and Signaling WG (teas) to consider the following document:
- 'RSVP-TE Extensions for Associated Bidirectional LSPs'
  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 2015-02-23. 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 describes Resource reSerVation Protocol (RSVP)
  extensions to bind two point-to-point unidirectional Label Switched
  Paths (LSPs) into an associated bidirectional LSP.  The association
  is achieved by defining new Association Types for use in ASSOCIATION
  and in Extended ASSOCIATION Objects.  One of these types enables
  independent provisioning of the associated bidirectional LSPs on both
  sides, while the other enables single sided provisioning.  The
  REVERSE_LSP Object is also defined to enable a single endpoint to
  specify all the parameters of an associated LSP in the single sided
  provisioning case.


The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-teas-mpls-tp-rsvpte-ext-associated-lsp/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-teas-mpls-tp-rsvpte-ext-associated-lsp/ballot/


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

  http://datatracker.ietf.org/ipr/2139/

AD review
=========

Authors,
                   
Thanks for this document which I found clear and not too long.

I have done my usual AD review to try to flush out any issues that
might otherwise show up in IETF last call or IESG review.

The only largish issue I have is about error conditions. Pretty much the
only error handling I see is in 5.3 where you have:

  An egress node, upon receiving a Path message containing an
  ASSOCIATION or Extended ASSOCIATION Object with Association Type set
  to "Single Sided Associated Bidirectional LSP" MUST create an LSP in
  the reverse direction or reject the Path message by sending a
  PathErr.

...but you don't say what reason code to give.

You need to handle some other error conditions such as...

**** race conditions
**** what if the association is triggered by both ends at the same time?
**** what if the reverse dirn LSP has already been associated with
    something else?

**** failure conditions
**** what if not willing or able to associate?
**** what if set-up of reverse LSP fails?
**** what if requested REVERSE LSP parameters are not acceptable?
**** what if the remote end point doesn't support the association                                     
    mechanism defined here? how will the initiator know?


I also have some smaller points as set out below.

I'll put the I-D into "revised I-D needed" state while we discuss these
points and while you produce an update.

Thanks for the work,
Adrian

====

You have a different number of font-page authors and names in the
Authors' Addresses section.

Looks like Fan Yang and Weilian Jiang should be moved to a
Contributors section.

---

Section 1 is OK, but it would have been better to just list the relevant
requirements (7, 11, 12, 50) and then the additional requirement (14).

Probably no need to change now, but my preference is to avoid the risk
of introducing an error during the copying or editorial process. If you
feel like making this change, I would be happier.

---

Because you use RBNF in section 4, you need to add a statement to
Section 2 like:

  This document uses the Routing Backus-Naur Form (RBNF) to define
  message formats as defined in [RFC5511].

And then, of course, add a normative reference.

---

I think 2.1.1 is missing an important statement about co-routing.

"A pair of reverse unidirectional LSPs that are associated to form an
associated bidirectional LSP do not necessarily follow the same path
through the network. If they do follow the same path, they are known as
'co-routed'."

---

3.1

  This section provides an overview and definition of the models for
  provisioning bidirectional LSPs.

This is missing the word "associated" to read "associated bidirectional"

---

Shouldn't 3.1.1 also mention the REVERSE_LSP Object. Something like...

  For the single sided provisioning, the Traffic Engineering (TE)
  tunnel is configured only on one endpoint.  An LSP for this tunnel is
  initiated by the initiating endpoint with the (Extended) ASSOCIATION
  Object inserted in the Path message.  The other endpoint then creates
  the corresponding reverse TE tunnel and signals the reverse LSP in
  response using information from the REVERSE_LSP Object if present.

---

3.1.2

Pedantry, but...

OLD
  For the double sided provisioning, two unidirectional TE tunnels are
  configured independently on both endpoints.
NEW
  For the double sided provisioning, two unidirectional TE tunnels are
  configured independently, one on each endpoint.
END

---

3.2

  This section provides an overview of the association signaling
  methods for the bidirectional LSPs.

Again, this is missing "associated"

---

3.2.1

OLD
  LSP1 is then signaled with an (Extended) ASSOCIATION Object inserted
  in the Path message, in which the Association Type indicating single
  sided provisioning.
NEW
  LSP1 is then signaled with an (Extended) ASSOCIATION Object inserted
  in the Path message, in which the Association Type indicating single
  sided provisioning is included.
END

---

3.2.2

OLD
  For the double sided provisioning model, both LSP1 and LSP2 are
  signaled independently with (Extended) ASSOCIATION Object inserted in
  the Path message, in which the Association Type indicating double
  sided provisioning.
NEW
  For the double sided provisioning model, both LSP1 and LSP2 are
  signaled independently with (Extended) ASSOCIATION Object inserted in
  the Path message, in which the Association Type indicating double
  sided provisioning is included.

---

3.2.2 needs to include some comment about how the two LSPs are selected
to be associated. I think this is simply "by management action applied
at both end points", although I wonder whether it is enough to apply the
action at just one end point because the association object will achieve
the desired result.

Please think about this and add a note.

---

Section 3.3.1 is fine as it is, but I think that it makes it look like
the REVERSE LSP object is only used for asymmetric b/w. Perhaps...

OLD
  As
  described in this document, addition of the REVERSE_LSP Object also
  allows the initiating node to control the reverse LSP by including
  other existing objects in a REVERSE_LSP Object.
NEW
  As
  described in Section 4.4, addition of the REVERSE_LSP Object also
  allows the initiating node to control other aspects of the reverse
  LSP (such as its path) by including other subobjects in a REVERSE_LSP
  Object.
END

---

For clarity 3.4 needs to observe that multiple association objects may
be present in the signaling of a single LSP.

---

4.2

      The new Association Types are defined as follows (values are
      temporary early allocations as per RFC7120):

Delete the bit in brackets, please, so that we don't accidentally find
it in the published RFC. Your message is already in 6.1 (which is good).
         
---

4.4.1

  Class_Num = 203 (of the form 11bbbbbb), C_Type = 1 (values are
  temporary early allocations as per RFC7120)

Same thing. Please remove the bit about early allocation.

(BTW, you have "of the form 11bbbbbb" twice in this section.

---

4.4.2 or 5.2

Maybe...

  The REVERSE_LSP object MUST NOT be included in a REVERSE_LSP object.

---

5.2

  An
  egress node MUST tear down and reestablish a new reverse LSP when
  REVERSE_LSP Object is either added or removed in the received Path
  message.

That's confusing!
- Why is modification of an existing LSP not allowed?
- Why does removal of the REVERSE_LSP object require tearing down and
  reestablishment since all that has happened is that the requirements
  for the reverse LSP have been relaxed?
- Why does addition of the REVERSE_LSP necessarily require tear down
  and reestablishment when the existing LSP might already satisfy the
  requirements?
- Is make-before-break used or is this assumed to be an out-of-service
  operation? If out-of-service you need to describe how that is
  achieved (e.g., using LI).

---

5.3 has

  If REVERSE_LSP Object is not present in the received Path message of
  the LSP, the egress node SHOULD use the LSP properties from the
  received LSP Path message to signal the LSP in the reverse direction
  (which may depend on the local policy).

This worries me. Do you mean that in the absence of a REVERSE_LSP object
containing an ERO, the reverse LSP MUST be co-routed with the forward
LSP?

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

Changes are expected over time. This version is dated 24 February 2012.

(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)?

Standards Track.

Why is this the proper type of RFC?

The docment defines RSVP related formats and behaviors.

Is this type of RFC indicated in the title page header?

Yes.

(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 describes Resource reSerVation Protocol (RSVP)
extensions to bind two point-to-point unidirectional Label
Switched Paths (LSPs) into an associated bidirectional LSP.
The association is achieved by defining new Association Types
for use in ASSOCIATION and in Extended ASSOCIATION objects.
One of these types enables independent provisioning of the
associated bidirectional LSPs on both sides, while the other
enables single sided provisioning.

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 document moved from the CCAMP to TEAS WGs as part
of the routing WG changes. This document has been fairly
noncontroversial.

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?

The base GMPLS protocol has been implemented. The extensions
defined in this document are compatible with earlier implementations.
While there have been no public statements on implementation, the
authors are from multiple vendors and an operator, and implementation
is expected. The Acknowledgement section acknowledges a
prototype implementation.

Personnel

Who is the Document Shepherd?

Deborah Brungard

Who is the Responsible Area
  Director?

Adrian Farrel

(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 reviewed the document as it has progressed
through the CCAMP WG. The Shepherd believes this document 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.


(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.

(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 specific 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.

Yes, see thread at
http://www.ietf.org/mail-archive/web/ccamp/current/msg16560.html

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

One related IPR, no concerns were expressed.

(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?

Solid among those who are interested. Strong concurrence of those
interested in MPLS-TP, with others being silent is a reasonable
characterization. 

(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 discontent seen.

(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.

The document passes ID 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.

No.

(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 IANA section was fully reviewed by the document shepherd. Two new
Association Type values, a new Class Number, and a new Class Type value,
are requested by the document. All of these values have temporary
early allocations as per RFC7120.


(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.

None.

(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.