Coordinated Multicast Trees (CMT) for Transparent Interconnection of Lots of Links (TRILL)
draft-ietf-trill-cmt-11

[Ballot comment]
1.1, 2nd paragraph: I assume the all-caps for "DOES NOT" are for emphasis, and we all know 2119 does not define that phrase. But it looks enough like 2119 language that it may confuse people.

Figure 2 is misaligned.

[Ballot comment]
Given the broad waiver written into the Applicability section, I am left to wonder about the more interesting multicast issues like interactions with IP multicast and actual distribution tree construction in TRILL.  I guess that is future work.

[Ballot comment]
I have a couple of significant concerns — I don't think are at the level of a DISCUSS and should be easily resolved.

1. What is a "virtual RBridge".  Is there a formal definition and a reference?  I think we can all pretty much guess what it is, but this is a standards track document and we shouldn't be guessing.  The Abstract ("Virtual representation of the non-TRILL network with a single Rbridge…") and Section 1.1 ("…a virtual Rbridge is used to represent multiple RBridges connected to an edge CE…") seem to attempt a definition, but one talks about a non-TRILL network and the other about RBridges which are TRILL constructs.

2. Section 5.6. (Failure scenarios) presents a failure recovery algorithm and says that "implementations MAY include other failure recover algorithms."  My concern is whether having different algorithms (in the same virtual RBridge group) can cause inconsistent performance or maybe even loops.  If so, then I think that fact should be called out and maybe a recommendation put forward to have one algorithm per group.

BTW, these are the same comments put forth in Stig Venaas' RTG-Dir review — but I didn't see a reply to that [https://mailarchive.ietf.org/arch/msg/rtg-dir/sdJci3nJ47BjpK4cm9LVWX36WZM].

[Ballot comment]
As mentioned by Tina in her OPS DIR review.

Section 5.7

After sentence about tunnelling, another sentence could be added as following.

“It should be noted that tunneling would require silicon change though CMT itself is software upgrading only.”



It can be also added in the introduction or abstract, CMT method doesn’t need hardware upgrade, this is the biggest advantage of CMT.

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

IANA has completed its review of draft-ietf-trill-cmt-08. If any part of this review is inaccurate, please let us know.

IANA has questions about this document's IANA Considerations section, which may need to be rewritten.

The section states, "This document requires no IANA actions because the ''Affinity Supported'' capability bit and the Affinity sub-TLV have been assigned in [RFC7176]."

However, this document is listed as the reference for the following TRILL-VER Sub-TLV Capability Flag registration:

0 Affinity sub-TLV support. [draft-ietf-trill-cmt]

We'll need to update this reference both when the document is approved for publication and when the document is 

Is the "Affinity sub-TLV" registration the registration of "AFFINITY" in the Sub-TLVs for TLV 144 registry at http://www.iana.org/assignments/isis-tlv-codepoints? If so, this registration has RFC 7176 as its reference. Should this document be listed as an additional reference for it?

The IANA Considerations section needs to be clear both about the fact that this document is the reference for the first registration, and about whether it is or isn't the reference for the second registration (if the second registration should be mentioned here).

Something along these lines could work, if it's correct to say that this document should be the reference for one but not the other:

"This document serves as the reference for TRILL-VER Sub-TLV Capability Flags registration "Affinity sub-TLV support." (bit 0).

"It mentions Sub-TLVs for TLV 144 registration "AFFINITY" (value 17), but should not be listed as a reference for that registration."

thanks,

Amanda Baber
IANA Senior Specialist
ICANN

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.

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Coordinated Multicast Trees (CMT) for TRILL) to Proposed Standard


The IESG has received a request from the Transparent Interconnection of
Lots of Links WG (trill) to consider the following document:
- 'Coordinated Multicast Trees (CMT) for TRILL'
  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 2015-10-05. 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


  TRILL facilitates loop free connectivity to non-TRILL networks via
  choice of an Appointed Forwarder for a set of VLANs. Appointed
  Forwarders provide load sharing based on VLAN with an active-standby
  model. High performance applications require an active-active load-
  sharing model. The Active-Active load-sharing model can be
  accomplished by representing any given non-TRILL network with a
  single virtual RBridge. Virtual representation of the non-TRILL
  network with a single RBridge poses serious challenges in multi-
  destination RPF (Reverse Path Forwarding) check calculations. This
  document specifies required enhancements to build Coordinated
  Multicast Trees (CMT) within the TRILL campus to solve related RPF
  issues. CMT provides flexibility to RBridges in selecting desired
  path of association to a given TRILL multi-destination distribution
  tree. This document updates RFC 6325.




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

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


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

  https://datatracker.ietf.org/ipr/2225/

Major Issues:

1) In Sec 5.3, it says "If an RBridge RB1 advertises an Affinity sub-TLV
with an AFFINITY RECORD that's ask for nickname RBn to be its child in
any tree and RB1 is not adjacent to a real or virtual RBridge RBn,
that AFFINITY RECORD is in conflict with the campus topology and MUST
be ignored."  How does an RBridge determine the connectivity of a
virtual RBridge RBn?  I can see that a Designated RBridge announces
the pseudo-nickname for the vDRB to the other RBridges in the LAALPs
(as described in draft-ietf-trill-pseudonode-nickname) but I don't see
any specific way that the connectivity of a virtual RBridge is
described and known by the other RBridges.  What am I missing?

Minor Issues:

2) In Sec 5.1, it talks about the tree number.  Is how the tree number
derived described elsewhere?  Is this something that each RBridge can
do independently?  Could you add a reference?

3) In Sec 5.1, could you clarify which RBridges are doing the
Distribution Tree provisioning?  I'm sure it's my lack of deep
familiarity, but until I got to Sec 5.2, it wasn't at all clear to me.

4) In Sec 5.6, it says "Timer T_j SHOULD be at least < T_i/2" Do you mean that timer T_j should be no more than T_i/2 or that timer T_j should be no less than T_i/2.  The "<" makes this unclear to me because the "at least" contradicts it; is it T_j < T_i/2 or T_i/2 < T_j.

(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, as indicated on the title page. This document
updates the TRILL distribution tree construction algorithm currently
specified in Proposed Standard RFC 6325.

(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:

The TRILL base protocol facilitates loop free connectivity to
non-TRILL networks via choice of an Appointed Forwarder for a set of
VLANs.  Appointed Forwarders provides load sharing based on VLAN with
an active-standby model. High performance operations require an
active-active load sharing model with rapid fail over and load
spreading on a per flow basis.  Active-Active load sharing can be
accomplished by representing any given non-TRILL network with a single
virtual RBridge. Virtual representation of the non-TRILL network with
a single RBridge poses serious challenges in multi-destination RPF
(Reverse Path Forwarding) check calculations.  This document specifies
required enhancements to build Coordinated Multicast Trees (CMT)
within the TRILL campus to solve RPF related issues.

  Working Group Summary:

This draft was developed by the WG over a two year period.  There has
been relatively little controversy over the technical content of the
draft. It has good WG support.

  Document Quality:

This document is of good quality. CMT is implemented in the Cisco
Nexus product line.

  Personnel:
    Document Shepherd:  Donald Eastlake, 3rd
    Responsible Area Director:  Alia Atlas

(3) Briefly describe the review of this document that was performed
    by the Document Shepherd.

The Shepherd provided some technical review and input to this
draft. The most recent Shepherd review is shown here:
http://www.ietf.org/mail-archive/web/trill/current/msg06618.html

(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 special 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.

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

Yes, see https://datatracker.ietf.org/ipr/2225/ by Dell Computer which
provides for non-assertion on a reciprocal basis and is believed to
relate to published patent application US20140071987 A1 "Systems and
methods providing reverse path forwarding compliance for a multihoming
virtual routing bridge". This IPR disclosure was not noted in the
first WG Last Call on this draft and a 2nd WG Last Call was
specifically held due to that oversight. There were no objections.

(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?

Many members of the WG have been involved in the development of
strategies to provide active-active support at the TRILL edge
[RFC7379] and support this draft with a reasonably broad 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.

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 nit errors.

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

No formal review required.

(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?

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, although there are references to standards documents of other
organizations which the nits checker finds as possible downrefs.

(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?

This draft updates RFC 6325 because implementation of CMT changes the
mandatory distribution tree construction algorithm in RFC 6325. This
update is indicated on the title page.

(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.

No IANA actions are required because the Affinity TLV was assigned by
[RFC7176]. 

(18) List any new IANA registries that require Expert Review for
    future allocations.

No new IANA registries are created.

(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.

None required.

(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, as indicated on the title page. This document
updates the TRILL distribution tree construction algorithm currently
specified in Proposed Standard RFC 6325.

(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:

The TRILL base protocol facilitates loop free connectivity to
non-TRILL networks via choice of an Appointed Forwarder for a set of
VLANs.  Appointed Forwarders provides load sharing based on VLAN with
an active-standby model. High performance operations require an
active-active load sharing model with rapid fail over and load
spreading on a per flow basis.  Active-Active load sharing can be
accomplished by representing any given non-TRILL network with a single
virtual RBridge. Virtual representation of the non-TRILL network with
a single RBridge poses serious challenges in multi-destination RPF
(Reverse Path Forwarding) check calculations.  This document specifies
required enhancements to build Coordinated Multicast Trees (CMT)
within the TRILL campus to solve RPF related issues.

  Working Group Summary:

This draft was developed by the WG over a two year period.  There has
been relatively little controversy over the technical content of the
draft. It has good WG support.

  Document Quality:

This document is of good quality. CMT is implemented in the Cisco
Nexus product line.

  Personnel:
    Document Shepherd:  Donald Eastlake, 3rd
    Responsible Area Director:  Ted Lemon

(3) Briefly describe the review of this document that was performed
    by the Document Shepherd.

The Shepherd provided some technical review and input to this
draft. The most recent Shepherd review is shown here:
http://www.ietf.org/mail-archive/web/trill/current/msg06618.html

(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 special 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.

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

Yes, see https://datatracker.ietf.org/ipr/2225/ by Dell Computer which
provides for non-assertion on a reciprocal basis and is believed to
relate to published patent application US20140071987 A1 "Systems and
methods providing reverse path forwarding compliance for a multihoming
virtual routing bridge". This IPR disclosure was not noted in the
first WG Last Call on this draft and a 2nd WG Last Call was
specifically held due to that oversight. There were no objections.

(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?

Many members of the WG have been involved in the development of
strategies to provide active-active support at the TRILL edge
[RFC7379] and support this draft with a reasonably broad 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.

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 nit errors.

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

No formal review required.

(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?

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, although there are references to standards documents of other
organizations which the nits checker finds as possible downrefs.

(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?

This draft updates RFC 6325 because implementation of CMT changes the
mandatory distribution tree construction algorithm in RFC 6325. This
update is indicated on the title page.

(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.

No IANA actions are required because the Affinity TLV was assigned by
[RFC7176]. 

(18) List any new IANA registries that require Expert Review for
    future allocations.

No new IANA registries are created.

(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.

None required.