IPv6 Support for Generic Routing Encapsulation (GRE)
draft-ietf-intarea-gre-ipv6-14

[Ballot comment]
Thanks for working through my Discuss about checksums and VPNs.

The version of the Discuss I cleared said this:

Thank you for working with me on this Discuss, and addressing my Comments. I've revised this Discuss based on conversations with Ron (and we're converging).

I have three questions, but I'm ready to clear.

For reference, the Checksum text in -13 now looks like this:

4.2.  Checksum Considerations

  As stated in [RFC2784], the GRE header can contain a checksum.  If
  present, the GRE header checksum can be used to detect corruption of
  the GRE header and GRE payload.

  The GRE header checksum cannot be used to detect corruption of the
  IPv6 delivery header.  Furthermore, the IPv6 delivery header does not
  contain a checksum of its own.  Therefore, no available checksum can
  be used to detect corruption of the IPv6 delivery header.

  In one failure scenario, the destination address in the IPv6 delivery
  header is corrupted.  As a result, the IPv6 delivery packet is
  delivered to a node other than the intended GRE egress node.
  Depending upon the state and configuration of that node, it will
  either:

  a.  Drop the packet

  b.  De-encapsulate the payload and forward it to its intended
      destination

  c.  De-encapsulate the payload and forward it to a node other than
      its intended destination.  For example, the payload might be
      intended for a node on one VPN, but delivered to an identically
      numbered node in another VPN.

  Behaviors a) and b) are acceptable.  Behavior c) is not acceptable.
  However, behavior c) is possible only when the payload destination
  address is not globally unique and the GRE egress node provides
  disambiguating context to that address.

  Before deploying GRE over IPv6, network operators should consider the
  likelihood of behavior c) in their network.  GRE over IPv6 MUST NOT
  be deployed other than where the network operator deems the risk
  associated with behavior c) to be acceptable.

  The risk associated with behavior c) could be mitigated with end-to-
  end authentication of the payload.
 
So, my questions are:

(1) how likely is it that endpoints in different VPNs would have overlapping address ranges?

(2) is it correct that if endpoint A gets traffic that was intended for an identically addressed endpoint B in another VPN using an overlapping address range, and that traffic is authenticated, endpoint A can say "this isn't for me", but if that traffic is not encrypted, is traffic intended for endpoint B leaking to endpoint A?

(3) if I'm not completely in the weeds so far, is "end-to-end authentication" something an operator can do? If the answer to (2) is "yes", is "end-to-end encryption" something an operator can do?

[Ballot discuss]
Thank you for working with me on this Discuss, and addressing my Comments. I've revised this Discuss based on conversations with Ron (and we're converging).

I have three questions, but I'm ready to clear.

For reference, the Checksum text in -13 now looks like this:

4.2.  Checksum Considerations

  As stated in [RFC2784], the GRE header can contain a checksum.  If
  present, the GRE header checksum can be used to detect corruption of
  the GRE header and GRE payload.

  The GRE header checksum cannot be used to detect corruption of the
  IPv6 delivery header.  Furthermore, the IPv6 delivery header does not
  contain a checksum of its own.  Therefore, no available checksum can
  be used to detect corruption of the IPv6 delivery header.

  In one failure scenario, the destination address in the IPv6 delivery
  header is corrupted.  As a result, the IPv6 delivery packet is
  delivered to a node other than the intended GRE egress node.
  Depending upon the state and configuration of that node, it will
  either:

  a.  Drop the packet

  b.  De-encapsulate the payload and forward it to its intended
      destination

  c.  De-encapsulate the payload and forward it to a node other than
      its intended destination.  For example, the payload might be
      intended for a node on one VPN, but delivered to an identically
      numbered node in another VPN.

  Behaviors a) and b) are acceptable.  Behavior c) is not acceptable.
  However, behavior c) is possible only when the payload destination
  address is not globally unique and the GRE egress node provides
  disambiguating context to that address.

  Before deploying GRE over IPv6, network operators should consider the
  likelihood of behavior c) in their network.  GRE over IPv6 MUST NOT
  be deployed other than where the network operator deems the risk
  associated with behavior c) to be acceptable.

  The risk associated with behavior c) could be mitigated with end-to-
  end authentication of the payload.
 
So, my questions are:

(1) how likely is it that endpoints in different VPNs would have overlapping address ranges?

(2) is it correct that if endpoint A gets traffic that was intended for an identically addressed endpoint B in another VPN using an overlapping address range, and that traffic is authenticated, endpoint A can say "this isn't for me", but if that traffic is not encrypted, is traffic intended for endpoint B leaking to endpoint A?

(3) if I'm not completely in the weeds so far, is "end-to-end authentication" something an operator can do? If the answer to (2) is "yes", is "end-to-end encryption" something an operator can do?

[Ballot comment]
This was the previous version of my Discuss - I'm moving it to the Comments section. Thanks for helping me better understand the situation.

In this text, in section 2.1,

  However, if the GRE Checksum Present field is set to zero, the GRE
  header is not protected by any checksum.  Furthermore, depending on
  which of the above-mentioned conditions are true, selected portions
  of the GRE payload will not be protected by any checksum.

  Network operators should evaluate risk factors in their networks and
  configure GRE ingress nodes appropriately.
 
What I'm trying to understand ("Discuss"), is what the risk factors actually look like for GRE over IPv6 in this draft.

The working assumption is that packets with corrupted addresses can be mis-delivered anywhere, and when you don't have a checksum that allows you to figure out that the packet has been corrupted, the accidental endpoint is going to try to deliver it to some unsuspecting application.

In GRE over UDP, we ended up with some conservative recommendations, because a corrupted UDP packet with no checksum could be misdelivered anywhere on the Internet.

I suspect that's also true for GRE directly over IPv6, but want to understand better before the document is approved.

The recommendations in https://tools.ietf.org/html/draft-ietf-tsvwg-gre-in-udp-encap-07#section-5.2 are (provided for your convenience):

  When UDP is used over IPv6, the UDP checksum is relied upon to
  protect both the IPv6 and UDP headers from corruption, and so MUST
  used with the following exceptions:

    a. Use of GRE-in-UDP in networks under single administrative
        control (such as within a single operator's network) where it
        is known (perhaps through knowledge of equipment types and
        lower layer checks) that packet corruption is exceptionally
        unlikely and where the operator is willing to take the risk of
        undetected packet corruption.

    b. Use of GRE-in-UDP in networks under single administrative
        control (such as within a single operator's network) where it
        is judged through observational measurements (perhaps of
        historic or current traffic flows that use a non-zero checksum)
        that the level of packet corruption is tolerably low and where
        the operator is willing to take the risk of undetected packet
        corruption.

    c. Use of GRE-in-UDP for traffic delivery for applications that
        are tolerant of mis-delivered or corrupted packets (perhaps
        through higher layer checksum, validation, and retransmission
        or transmission redundancy) where the operator is willing to
        rely on the applications using the tunnel to survive any
        corrupt packets.

  For these exceptions, the UDP zero-checksum mode can be used.
 
A similar set of recommendations are included in https://tools.ietf.org/html/rfc7510#section-3.2, for MPLS over UDP.

My previous comments (reproduced below) have already been addressed. Thank you!
 
We have a conversation about the risk factors pretty much every time we talk about turning checksums off, and often, we start without a shared understanding of what can go wrong. I'm wondering if there's a canonical description of the risks that could be referenced here. I've asked TSV-DIR if one exists (so, no action for the draft authors, unless you already have a reference in mind), but in the absence of a reasonable reference, a forward pointer to section 4.2 might be helpful.

In this text, in section 3.2,

  Before activating a GRE tunnel and periodically thereafter, the GRE
  ingress node MUST execute procedures that verify the tunnel's ability
  to carry a 1280-byte IPv6 payload packet from ingress to egress,
  without fragmenting the payload.  Having executed those procedures,
  the GRE ingress node MUST activate or deactivate the tunnel
  accordingly.
 
I understand "MUST deactivate" (thank you), but wonder if "activate" is a MUST here.

[Ballot discuss]
I'm balloting this question as Discuss because we haven't had a chance to close on it in e-mail yet. To be clear, I'm sure we'll be able to do that fairly quickly.

In this text, in section 2.1,

  However, if the GRE Checksum Present field is set to zero, the GRE
  header is not protected by any checksum.  Furthermore, depending on
  which of the above-mentioned conditions are true, selected portions
  of the GRE payload will not be protected by any checksum.

  Network operators should evaluate risk factors in their networks and
  configure GRE ingress nodes appropriately.
 
What I'm trying to understand ("Discuss"), is what the risk factors actually look like for GRE over IPv6 in this draft.

The working assumption is that packets with corrupted addresses can be mis-delivered anywhere, and when you don't have a checksum that allows you to figure out that the packet has been corrupted, the accidental endpoint is going to try to deliver it to some unsuspecting application.

In GRE over UDP, we ended up with some conservative recommendations, because a corrupted UDP packet with no checksum could be misdelivered anywhere on the Internet.

I suspect that's also true for GRE directly over IPv6, but want to understand better before the document is approved.

The recommendations in https://tools.ietf.org/html/draft-ietf-tsvwg-gre-in-udp-encap-07#section-5.2 are (provided for your convenience):

  When UDP is used over IPv6, the UDP checksum is relied upon to
  protect both the IPv6 and UDP headers from corruption, and so MUST
  used with the following exceptions:

    a. Use of GRE-in-UDP in networks under single administrative
        control (such as within a single operator's network) where it
        is known (perhaps through knowledge of equipment types and
        lower layer checks) that packet corruption is exceptionally
        unlikely and where the operator is willing to take the risk of
        undetected packet corruption.

    b. Use of GRE-in-UDP in networks under single administrative
        control (such as within a single operator's network) where it
        is judged through observational measurements (perhaps of
        historic or current traffic flows that use a non-zero checksum)
        that the level of packet corruption is tolerably low and where
        the operator is willing to take the risk of undetected packet
        corruption.

    c. Use of GRE-in-UDP for traffic delivery for applications that
        are tolerant of mis-delivered or corrupted packets (perhaps
        through higher layer checksum, validation, and retransmission
        or transmission redundancy) where the operator is willing to
        rely on the applications using the tunnel to survive any
        corrupt packets.

  For these exceptions, the UDP zero-checksum mode can be used.
 
A similar set of recommendations are included in https://tools.ietf.org/html/rfc7510#section-3.2, for MPLS over UDP.

[Ballot comment]
My previous comments (reproduced below) have already been addressed. Thank you!
 
We have a conversation about the risk factors pretty much every time we talk about turning checksums off, and often, we start without a shared understanding of what can go wrong. I'm wondering if there's a canonical description of the risks that could be referenced here. I've asked TSV-DIR if one exists (so, no action for the draft authors, unless you already have a reference in mind), but in the absence of a reasonable reference, a forward pointer to section 4.2 might be helpful.

In this text, in section 3.2,

  Before activating a GRE tunnel and periodically thereafter, the GRE
  ingress node MUST execute procedures that verify the tunnel's ability
  to carry a 1280-byte IPv6 payload packet from ingress to egress,
  without fragmenting the payload.  Having executed those procedures,
  the GRE ingress node MUST activate or deactivate the tunnel
  accordingly.
 
I understand "MUST deactivate" (thank you), but wonder if "activate" is a MUST here.

[Ballot discuss]
I'm confused by "It updates the GRE specification, RFC 2784." and "This document specifies GRE procedures for IPv6, used as either the payload or delivery protocol."

Let me take this sentence (in the GRE Header Fields)

  The GRE ingress node SHOULD set the Checksum Present field in the GRE
  header to zero.

I don't know if it's valid for both IPv4 and IPv6.
Based on the "update" flag, I would say it's valid for both, as it updates RFC 2784.
Based on the abstract, I would say it's only for IPv6
If the latter, it should clearly say so. Alternatively, the "update" can be removed, to treat this RFC as an extension, specific to IPv6. However, we would lose the forward ref from RFC 2784

[Ballot comment]
I have a few minor comments:

-- 3.2, 2nd paragraph:

As worded, I expected to find defined procedures (or a citation to such) to accomplish the verification. I see from the following paragraph that this is not the case. I think the following change would be more clear:

OLD
  Before activating a GRE tunnel and periodically thereafter, the GRE
  ingress node MUST execute procedures that verify the tunnel’s ability
  to carry a 1280-byte IPv6 payload packet from ingress to egress,
  without fragmenting the payload.
NEW
  Before activating a GRE tunnel and periodically thereafter, the GRE
  ingress node MUST verify the tunnel’s ability
  to carry a 1280-byte IPv6 payload packet from ingress to egress,
  without fragmenting the payload.
END

-- 3.2, last paragraph:
Do all such existing implementations have the ability to be configured to fragment and reassemble payload packets? That is, is there a class of existing implementation that can no longer be considered compliant?

-- 3.3, last sentence:
Is there a reciprocal requirement for the egress to reassemble the fragmented delivery header?

-- 4.2, 2nd to last paragraph:
This seems like a very subjective MUST NOT. Please consider stating this without 2119 keywords.

-- 8.1, first reference:
That’s probably not appropriate as a normative reference. Neither the URL or the content can be assumed to be stable. Would it make sense to reference RFC 7042 instead?

** Nits **

--1, first sentence:
s/Generic Routing Encapsulation/The Generic Routing Encapsulation/

-- 3
s/carry IPv6 payload/carry an IPv6 payload/    ; (or /carry IPv6 payloads/)

-- 3.1
It would be helpful to mention that this is the IPv6 ether type.

[Ballot comment]
The draft looks good, but I do have one item to chat about that should be very easy to address.  Its subtle wording, but I think it is important.  Thanks.

Surprisingly, RFC4023 does a pretty good job explaining the threats that IPsec encryption and authentication help mitigate.  The wording in the security section of this draft reads to me as if you can use either encryption or authentication to address those threats.  I'm pretty sure that was not intended as each assists to mitigate different threats, clearly described in RFC4023.

The Security Considerations has the following text right now:
  These threats apply to
  any GRE payload.  As stated in RFC 4023, these threats can be
  mitigated by authenticating and/or encrypting the delivery packet
  using IPsec [RFC4301].  Alternatively when the payload is IPv6, these
  threats can also be mitigated by authenticating and/or encrypting the
  payload using IPsec, instead of the delivery packet.

How about something like the following (feel free to propose something else):
  These threats apply to
  any GRE payload.  As stated in RFC 4023, the various threats can be
  mitigated through options such as authenticating and/or encrypting the delivery packet
  using IPsec [RFC4301].  Alternatively when the payload is IPv6, these
  threats can also be mitigated by authenticating and/or encrypting the
  payload using IPsec, instead of the delivery packet.

If it is changed in the first sentence, I think it makes the second one follow a bit better without changes.

[Ballot comment]
In this text, in section 2.1,

  However, if the GRE Checksum Present field is set to zero, the GRE
  header is not protected by any checksum.  Furthermore, depending on
  which of the above-mentioned conditions are true, selected portions
  of the GRE payload will not be protected by any checksum.

  Network operators should evaluate risk factors in their networks and
  configure GRE ingress nodes appropriately.
 
We have a conversation about the risk factors pretty much every time we talk about turning checksums off, and often, we start without a shared understanding of what can go wrong. I'm wondering if there's a canonical description of the risks that could be referenced here. I've asked TSV-DIR if one exists (so, no action for the draft authors, unless you already have a reference in mind), but in the absence of a reasonable reference, a forward pointer to section 4.2 might be helpful.

In this text, in section 3.2,

  Before activating a GRE tunnel and periodically thereafter, the GRE
  ingress node MUST execute procedures that verify the tunnel's ability
  to carry a 1280-byte IPv6 payload packet from ingress to egress,
  without fragmenting the payload.  Having executed those procedures,
  the GRE ingress node MUST activate or deactivate the tunnel
  accordingly.
 
I understand "MUST deactivate" (thank you), but wonder if "activate" is a MUST here.

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

IANA has reviewed draft-ietf-intarea-gre-ipv6-09, which is currently in Last Call, and has the following comments:

We understand that this document doesn't require any IANA 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, IANA does not 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:  (IPv6 Support for Generic Routing Encapsulation (GRE)) to Proposed Standard


The IESG has received a request from the Internet Area Working Group WG
(intarea) to consider the following document:
- 'IPv6 Support for Generic Routing Encapsulation (GRE)'
  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 2015-07-09. 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


  Generic Routing Encapsulation (GRE) can be used to carry any network-
  layer payload protocol over any network-layer delivery protocol.  GRE
  procedures are specified for IPv4, used as either the payload or
  delivery protocol.  However, GRE procedures are not specified for
  IPv6.

  This document specifies GRE procedures for IPv6, used as either the
  payload or delivery protocol.  It updates the GRE specification, RFC
  2784.





The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-intarea-gre-ipv6/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-intarea-gre-ipv6/ballot/


No IPR declarations have been submitted directly on this I-D.

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)?  Why
is this the proper type of RFC?  Is this type of RFC indicated in the
title page header?

  Proposed Standard.

  The document has received significant community review, and appears
  to enjoy enough community interest to be considered valuable. It defines
  GRE procedures for IPv6, updating RFC 2784, which is has the status of
  Proposed Standard.

  The RFC type is indicated in the document header page.

(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 document specifies GRE procedures for IPv6, when used either as payload
  or delivery protocol. Generic Routing Encapsulation (GRE) can be used to carry
  any network-layer payload protocol over any network-layer delivery protocol.
  GRE procedures are specified for IPv4 in RFC 2784, but are not defined for IPv6.

  The document describes how GRE for IPv6 has been implemented by several vendors.

Working Group Summary

  The normal WG process was followed and the document has been discussed for several
  cycles. The document as it is now, reflects WG consensus, with nothing special worth noting.

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 document describes how GRE for IPv6 has been implemented
  by several vendors, so there exist implementations of the mechanisms
  described in the document.

  The document has received multiple thorough reviews in the WG.

Personnel

  Carlos J. Bernardos (cjbc@it.uc3m.es) is the document shepherd.
  Brian Haberman (brian@innovationslab.net) is the AD.
 
(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
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  The Document Shepherd has personally done a thorough review of the
  document. Some changes (mainly editorial) were requested to the
  authors and included in the last revision of the draft. The Document
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  IDnits only reports about the document creation date being in past and some other minor comments that seem to be fine.

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If so, list these downward references to support the Area Director in
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  None needed.

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)?  Why
is this the proper type of RFC?  Is this type of RFC indicated in the
title page header?

  Proposed Standard.

  The document has received significant community review, and appears to enjoy enough community interest to be considered valuable. It defines  GRE procedures for IPv6, updating RFC 2784, which is has the status of Proposed Standard.

  The RFC type is indicated in the document header page.

(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 document specifies GRE procedures for IPv6, when used either as payload or delivery protocol. Generic Routing Encapsulation (GRE) can be used to carry any network-layer payload protocol over any network-layer delivery protocol. GRE procedures are specified for IPv4 in RFC 2784, but are not defined for IPv6.

  The document describes how GRE for IPv6 has been implemented by several vendors.

Working Group Summary

  The normal WG process was followed and the document has been discussed for several cycles. The document as it is now, reflects WG consensus, with nothing special worth noting.

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 document describes how GRE for IPv6 has been implemented by several vendors, so there exist implementations of the mechanisms described in the document.

  The document has received multiple thorough reviews in the WG.

Personnel

  Carlos J. Bernardos (cjbc@it.uc3m.es) is the document shepherd.
  Brian Haberman (briad@innivationslab.net) is the AD.
 
(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 personally done a thorough review of the document. Some changes (mainly editorial) were requested to the authors and included in the last revision of the draft. The Document Shepherd believes the document is ready for forwarding to IESG for publication.

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

  The Document Shepherd has no concerns about the depth or breadth of these reviews.

(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.

  The Document Shepherd has 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.

  Yes.

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

  No IPRs declared.

(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? 

  There is WG consensus behind this document.

(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.

  IDnits only reports about the document creation date being in past and some other minor comments that seem to be fine.

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

  None needed.

(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 document makes no request of 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.

  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.

  None needed.