Using Only Link-Local Addressing inside an IPv6 Network
draft-ietf-opsec-lla-only-11

[Ballot comment]
I promised to drop my DISCUSS at the end of the telechat.  There was rather overwhelming advice from operators who actually have large deployments in the field that this was a bad idea, and I think that should be reflected in the document, but I'm not going to actively block the document because the text doesn't currently reflect that message.

That said, I would like to see the text updated to clearly say that some experienced operators consider this a bad idea, and that operators who are considering deploying this method should bear that in mind and not take the fact that this document has been published by the IETF as an indication that this is a preferred method of deployment.

[Ballot discuss]
I'm raising this as a DISCUSS for the meeting today because I don't know what the outcome of the discussion we had about this back in April/May was.  It looks like this text is the result of that discussion (it appears to be the only change since the discussion):

  During WG and IETF last call the technical correctness of the
  document has been reviewed, however debate exists as to whether to
  recommend this technique.  The deployment of this technique is
  appropriate where it is found to be necessary.

This doesn't seem to entirely capture the opinions that were stated during IETF last call.  Do we feel that the last call comments have been adequately addressed?  I don't have a strong opinion on this either way; I just want to make sure we actually talk about it on the telechat, given our recent penchant for brevity.  Regardless of the outcome of that discussion, I will drop the DISCUSS after the telechat is done.

[Ballot comment]
I have not seen a response to Peter Yee's Gen-ART review, although some of the suggested issues have been corrected.

FWIW, I still think Peter was right in these two items that have not been changed:

Page 4, 5th paragraph, 2nd sentence: SSH brute force password attacks aren't
really reduced unless the reduction is simply not being able to attack a
single router over multiple interfaces in parallel.  A better scheme for
reducing SSH brute force password attacks might be to limit the rate of
responses to SSH login attempts in the face of repeated failures.
Considering dropping this marginal example.

Page 6, 1st partial paragraph: the argument is made that "more work" is
required to discover all of an IXPs loopback interface addresses before a
generic attack can be mounted.  This wouldn't seem to be a lot of upfront
work and once it has been done, the advantage is negated.  I don't find the
argument particularly persuasive.

[Ballot comment]
  During WG and IETF last call the technical correctness of the
  document has been reviewed, however debate exists as to whether to
  recommend this technique.  The deployment of this technique is
  appropriate where it is found to be necessary.

Wow. The above (especially the second sentence), along with the shepherd writeup, does make one wonder whether the WG really wanted to publish this document. I'm not about to stand in the way, but to say that the "technique is appropriate where it is found to be necessary" is not a very meaningful claim.

[Ballot comment]

nitty nits only:

section 1: "attack horizon" isn't the usual phrase, "attack
surface" is I think more common (and is used later for this).

section 1: "The deployment of this technique is appropriate
where it is found to be necessary" seems to be a tautology.

2.4: I think uRPF and PTMUd are used without expansion.
(And why the small 'd' in PMTUd, don't recall that before.)

[Ballot comment]

section 1: "attack horizon" isn't the usual phrase, "attack
surface" is I think more common (and is used later for this).

section 1: "The deployment of this technique is appropriate
where it is found to be necessary" seems to be a tautology.

2.4: I think uRPF and PTMUd are used without expansion.
(And why the small 'd' in PMTUd, don't recall that before.)

[Ballot comment]
Overall, I think this is a well written draft and think the security benefits could be very positive. 

In section 2.2, could you move up the reference to RFC6752 and then you can avoid the last sentence in this section.  I think it makes it cleaner and leads you right to the detailed description for iACL.

Suggest change from: "This may
  ease protection measures, such as infrastructure access control lists
  (iACL)."
To: "This may
  ease protection measures, such as infrastructure access control lists
  (iACL). [RFC6752]" 

I agree with the point made in this paragraph and think another advantage is that you can define ACLs for the pass through traffic at this point that is 'invisible' for direct attacks.  Some firewalls operate in what they call bridge mode for that purpose.

Please see the recommendation in the SecDir review to include references to security considerations sections in previously mentioned RFCs in the draft.  Here's a link in case you didn't see it.

https://www.ietf.org/mail-archive/web/secdir/current/msg04709.html

[Ballot comment]
= Section 2.3 =
If it seems reasonable, might it be possible to say "LLAs have usually been EUI-64 based" rather than "LLAs are usually EUI-64 based" given that there is some movement away from embedding hardware addresses in IIDs (e.g., draft-ietf-6man-default-iids)?

[Ballot comment]
I have no strong objection to the publication of this document although
there is to me a faint whiff of what a sceptic might call snake oil.
Some of that arises from an imbalance of language ("advantages"
against "caveats" rather than "opportunities" against "disadvantages")
and some of it could have been dispelled by answering the shepherd
write-up question on implementation by describing the existing
deployments that use this technique.

Anyway, here are two editorial issues for you to consider...

Are the last two paragraphs of 2.2 in the right section? They do not
appear to describe "advantages" of the proposed scheme.

The text "using only link-local addresses on infrastructure links" is
lumpy to read, but does convey exactly what you mean. There is a
temptation to read it as "using link-local addresses only on
infrastructure links" and you will need to watch the RFC Editor to make
sure that bug doesn't creep in. And you will need to fix Section 3
where you have
  Using LLAs only on infrastructure links reduces the attack surface of
  a router

[Ballot discuss]
I believe there is an additional that should be discussed in this document, but I want to get the authors' opinions on it.

The document makes the claim that using LLAs between infrastructure devices reduces the attack surface of the network.  However, I think there is an adverse side effect that needs to be discussed.  If every device in a network follows this advice and only uses a globally-scoped address on its loopback interface, it seems easier to map the topology of the network.  Since all responses to pings/traceroutes from a single router will have the same global address, an attacker can map adjacent devices by probing from different points outside the network.  In the non-LLA case, responses to pings/traceroutes typically use the interface addresses, which would vary in the same type of probing.  By reducing the number of addresses that can be used in ping/traceroute responses, the LLA-only network is more vulnerable to network mapping.

IESG/Authors/WG Chairs:

IANA has reviewed draft-ietf-opsec-lla-only-07, which is currently in Last Call, and has the following comments:

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

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

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

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Using Only Link-Local Addressing Inside an IPv6 Network) to Informational RFC


The IESG has received a request from the Operational Security
Capabilities for IP Network Infrastructure WG (opsec) to consider the
following document:
- 'Using Only Link-Local Addressing Inside an IPv6 Network'
  as Informational RFC

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 2014-04-07. 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


  In an IPv6 network it is possible to use only link-local addresses on
  infrastructure links between routers.  This document discusses the
  advantages and disadvantages of this approach to help the decision
  process for a given network.




The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-opsec-lla-only/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-opsec-lla-only/ballot/


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

Document Shepherd Write-Up


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?


Type of RFC Requested: Informational
Why: This document provides information to the operator community regarding the advantages and disadvantages of exclusively using LLA addresses on infrastructure links in a network. This document neither prescribes a preferred method of deployment nor makes any changes to protocols.


(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.

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?

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?

Personnel

  Who is the Document Shepherd? Who is the Responsible Area
  Director?

Technical Summary
In an IPv6 network it is possible to use only link-local addresses on
infrastructure links between routers.  This document discusses the
advantages and disadvantages of this approach to help the decision
process for a given network.

Working Group Summary
This document had a bumpy ride within the working group. There is rough consensus that the document provides valuable insight into advantages and disadvantages of the network Link-Local approach and that the content it includes is technically correct. The bumps for this document have been driven by the believe that running a network based upon this approach is a general bad idea, and that even existence of this document provides perception it is an IETF supported approach.

Document Quality
The document is technically correct as seen by many reviews on the WG email list.
The document does not discuss a new protocol or implementation of a new protocol. The document provides advantages and disadvantages of using IPv6 Link-Local Addresses within an IPv6 Network. It has had thorough review by WG reviewers, with discussions inside the WG email list

Personnel
Area Director: Joel Jaeggli
Shepherd: Gunter Van de Velde



(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.


Document is ready for IESG review



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


The document has been sufficiently reviewed by knowledgeable reviewers of the OPSEC WG community


(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 special additional review required


(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.


In the OPSEC WG people have stated that eventhough they do not like the LLA approach, that here is value and support in publication of the advantages and disadvantages, because proper addressing is a key network architecture question. As Shepherd I see a need for documenting this in an IETF document as it is a question when architecting a Network.


(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.


IPR reminder sent out on 11 February.
Authors confirmed to not be aware of IPR attached to the document.



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


None


(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? 

I believe there is strong consensus that it is good to have a repository of advantages and disadvantages. There is agreement that the LLA draft should for sure not recommend the addressing approach discussed.



(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 threatening of appeal, or extreme discontent (some discontent is seen, but of not extreme level)



(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.


-06 has few idnits of informational reference matter
idnits 2.13.01

tmp/draft-ietf-opsec-lla-only-06.txt:
  Attempted to download rfc0495 state...
  Failure fetching the file, proceeding without it.
  Attempted to download rfc0792 state...
  Failure fetching the file, proceeding without it.

  Checking boilerplate required by RFC 5378 and the IETF Trust (see
  http://trustee.ietf.org/license-info):
  ----------------------------------------------------------------------------

    No issues found here.

  Checking nits according to http://www.ietf.org/id-info/1id-guidelines.txt:
  ----------------------------------------------------------------------------

    No issues found here.

  Checking nits according to http://www.ietf.org/id-info/checklist :
  ----------------------------------------------------------------------------

    No issues found here.

  Miscellaneous warnings:
  ----------------------------------------------------------------------------

  -- The document date (January 6, 2014) is 36 days in the past.  Is this
    intentional?


  Checking references for intended status: Informational
  ----------------------------------------------------------------------------

  == Unused Reference: 'RFC0792' is defined on line 353, but no explicit
    reference was found in the text

  == Outdated reference: A later version (-02) exists of
    draft-ietf-opsec-bgp-security-01


    Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).

    Run idnits with the --verbose option for more detailed information about
    the items above.



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

This document is purely informational, no new protocol design/architecture, mibs, etc discussed.


(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 normative references


(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.

There are no normative 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.


No, the publication will not change any existing RFCs



(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).


No IANA considerations within the document


(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 IANA considerations within the document


(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.


Informational document using traditional English.