Subject: Fwd: Summary of the LLMNR Last Call

From: Margaret Wasserman <[email-masked]>
Date: Mon, 19 Sep 2005 08:19:49 -0400

Sorry, I mistyped "namedroppers" on this message the first time...

Margaret

>Date: Sun, 18 Sep 2005 10:09:07 -0400
>To: [email-masked]
>From: Margaret Wasserman <[email-masked]>
>Subject: Summary of the LLMNR Last Call
>Cc: [email-masked], [email-masked]
>Bcc:
>X-Attachments:
>
>
>Hi All,
>
>As I am sure many of you have noticed, there was extensive 
>discussion during the IETF Last Call for the "Link Local Multicast 
>Name Resolution (LLMNR)" specification that is currently available 
>as draft-ietf-dnsext-mdns-43.txt.  Thanks to all who participated! 
>The discussion appears to have quieted down at this point, so I will 
>attempt to summarize the discussion and see if we can reach some 
>conclusions.
>
>First, I'll give a brief summary of the responses received:
>
>By my count 38 separate individuals responded to the Last Call. 
>Some of these people responded on the IETF list, some on the IESG 
>list, and some privately to me.  People who responded privately to 
>others were not counted  :-).
>
>Of the 38 respondents, only 18 of them stated an explicit opinion on 
>the publication of LLMNR as a Proposed Standard RFC.  Others 
>provided useful facts to inform the discussion and/or discussed 
>other topics, such as the structure of the DNS root.  I was quite 
>conservative about how I determined people's opinions, and I tried 
>not to infer peoples' opinions from factual statements about only 
>one of the protocols, etc.
>
>Of the 18 people who expressed an explicit opinion, 14 people argued 
>against the publication of LLMNR as a Proposed Standard.  I realize 
>that we don't vote on specifications in the IETF.  I also realize 
>that the IETF LC is worded to encourage the statements of objection 
>and not to encourage statements of support.  However, the fact that 
>14 separate individuals felt strongly enough that this document 
>should not be published to say so explicitly in response to an IETF 
>LC must be taken quite seriously.
>
>In addition to a few minor nits or comments, all of which have been 
>captured in the issue tracker, there seem to be three major concerns 
>with the publication of this protocol:
>
>(1) Concerns that publication of this protocol will be confusing or 
>actively harmful given the existing wide deployment of Apple's mDNS 
>protocol.
>
>Concerns here seem to hinge on whether end-users will use .local 
>extensions because they _think_ that they have mDNS available when 
>they actually do not, which, when combined with LLMNR's default 
>behavior of querying the DNS first, will result in a larger number 
>of .local lookups in the global DNS.  There are several possible 
>ways to alleviate this issue, including suppression of global 
>queries for .local domains as part of an LLMNR implementation, or 
>suppressing recursive lookups for names in the .local domain on the 
>local DNS server, but none of these solutions is currently specified 
>in the LLMNR specification or elsewhere.
>
>(2) Security concerns have been raised about the fact that 
>applications on hosts that implement LLMNR will not be able to tell 
>if a response has come from the DNS or from a local lookup.
>
>This opens applications to attack from nodes that can block global 
>DNS access and substitute local resolution.  Some ways to eliminate 
>or alleviate this issue might include:  using different domains 
>(such as .local) to distinguish global and local lookups, explicitly 
>using different global and local lookup mechanisms at the 
>application level, only falling back to local resolution when a "no 
>such name" response is received from the global DNS, placing further 
>limits on what answers are acceptable from local lookups (only for 
>certain domains configured as local, only within certain IP 
>subnets...).
>
>This security concern does not seem to be adequately explored and 
>addressed in the LLMNR specification.  At the very minimum, it 
>should be carefully explored in the security considerations section 
>so that implementers and users can be aware of these concerns.
>
>(3) Separate, but perhaps underlying both of the previous issues, 
>there seems be a fundamental disagreement about what technical 
>approach we should take to link-local name lookup.  LLMNR takes the 
>approach that local lookups should use the same names as global 
>lookups and that upper layers should not care whether a name was 
>resolved in the global DNS or locally, essentially making the local 
>lookup mechanism an extension of the DNS.  mDNS takes the approach 
>that local lookups should be distinguishable from global lookups and 
>accomplishes this through the use of a special local domain (.local).
>
>This is an issue that has been discussed extensively in the DNSEXT 
>WG at various times, and consensus was found to proceed with the 
>LLMNR approach.  However, it is not clear whether that consensus is 
>held by the wider IETF community, as there are at least 14 people in 
>the IETF who have explicitly disagreed with that decision during 
>IETF LC.
>
>So, based on the IETF LC discussion of this document, I have come to 
>two conclusions:
>
>CONCLUSION 1:  There are at least two blocking technical issues with 
>the LLMNR specification (raised in items #1 and #2 above) that would 
>need to be resolved before this document is technically ready for 
>publication as an Proposed Standard RFC.  We should resolve these 
>issues and determine that the IETF community is satisfied with their 
>resolution before sending the document to IESG review.
>
>CONCLUSION 2: The IETF community does not currently have consensus 
>to standardize a local name resolution mechanism that takes the 
>approach described in LLMNR.  Further work would be needed to 
>establish the IETF consensus required to publish this document as a 
>Proposed Standard.
>
>Based on these conclusions, I do not intend to forward the LLMNR 
>specification to the IESG for review and approval.  I am planning to 
>send the document back to the WG for resolution of these issues and 
>would issue another IETF LC if/when the WG believes that they have a 
>document that will address these issues and reach IETF consensus.
>
>We have a number of choices about how to proceed in this situation, 
>but before we talk about next steps, I would like to hear any 
>feedback that people might have regarding my summary of the 
>discussion so far and the conclusions that I have reached from it.
>
>Margaret
>
>
>

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---

From: Margaret Wasserman <[email-masked]>
Date: Wed, 21 Sep 2005 11:06:52 -0400

Hi Robert,

Our process, as currently instantiated, has three stages after a 
document is submitted to the IESG for review/approval:

1. AD Review -- the responsible AD reviews the document and 
determines if is ready for IETF LC.  Sometimes other things happen at 
this stage, like review by certain specialist groups (such as the MIB 
doctors) and/or resolution of AD Review comments.
2. IETF LC -- the document goes to IETF LC, after which the 
responsible AD determines whether the community has consensus to 
publish the document.  Any issues raised in IETF LC need to be 
addressed before he document is approved by the IESG.
3. IETF Evaluation -- the full IESG reviews the document on a 
telechat, stating positions (yes, no objection, discuss, abstain or 
recuse) on the document.  Any discuss positions have to be resolved 
before the document is forwarded to the RFC editor for publication. 
For a standards track document, there must also be at least one 'yes' 
position and at least 9 'yes/no-ob' positions for a document to be 
approved for publication.

It was my job (as responsible AD for DNSEXT) to perform the AD 
review, send the document to IETF LC, determine whether or not we 
have IETF consensus to publish the documen and make sure that any 
substantive issues raised during IETF LC are addressed before sending 
the document to the IESG for review.

In my opinion, based on the results of the IETF LC, the IETF LC 
raised two substantive technical issues with this specification, and 
the IETF community does not currently have consensus to publish this 
document as a Proposed Standard.  If the WG continues to believe that 
this document should be published as a Proposed Standard, they will 
address these technical issues (through changes to the document, 
informing the community why changes are not needed, or other means) 
and produce a document that will achieve IETF community consensus.

Like all decisions made by ADs, my decision is, of course, subject to appeal.

Margaret

At 9:32 PM +0700 9/21/05, Robert Elz wrote:
>     Message-ID:  <p0620071dbf52f99dab4c@[192.168.2.2]>
>
>I am not going to comment on the substance of the issues, or the
>doc in question, as I haven't been following what is happening with
>it, nor have a read a recent version.
>
>But ...
>
>   | Based on these conclusions, I do not intend to forward the LLMNR
>   | specification to the IESG for review and approval.
>
>What kind of process is going on here?    As I recall it, from rfc2026,
>it is the IESG that issues last calls, when it has a doc for review, and
>the IESG that decides if a last call has passed or not (that is, the IESG
>takes input from the comments received during the last call to help it make
>its decision on what to do with the doc that has been presented to it).
>
>How did we ever get an IETF last call on a doc that hasn't even gone to
>the IESG (apparently) but is still (apparently) under AD review ?
>
>And how does one AD (alone, apparently) get to draw conclusions based upon
>the results of the last call ?
>
>What is happening here?   Can't the IETF manage to either follow its
>own documented processes, or change them in the approved way?
>
>kre

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