Congestion Exposure (ConEx) Concepts, Abstract Mechanism, and Requirements
draft-ietf-conex-abstract-mech-13

[Ballot comment]

(Apologies, I only had time to skim this one, so
my comments might be a bit off the mark - feel
free to tell me I'm being dumb if so:-)

- The IPR declaration says licensing is to be provided
"later" though a note in fact does seem to contain a
(nice) set of terms. Might be good to fix?

- Could conex signals be used as part of an oracle
attack? I'm not sure they could but has someone
thought about that? If not, and if there were a way in
which to abuse conex along those lines then it could
be that stating a requirement that specific protocols
consider this would be a good idea. Note that I'm not
sure if a feasible way to use conex in such an attack
exists. If it did, a simple countermeasure might be to
just not allow for very fine-grained signals.

- It'd be good if the security considerations here
considered how more and more use of ciphertext might
affect conex, in particular for the proxy or audit
functionality. For example, is there any interplay
with what tcpinc is likely to produce?

[Ballot comment]
I am glad for the existence of this document. Thanks for taking the time
to write it.

Alissa's first comment needs to be addressed.

[Ballot comment]
= Section 2 =
"This document extends the capabilities of the Internet protocol suite
  with the addition of a new Congestion Exposure signal."

This document doesn't do that, right? Maybe one of the standards-track conex documents will, but this document does not directly affect the Internet protocol suite.

"ConEx represents a recognition that the
  IETF cannot regulate this space directly because it concerns the
  behaviour of users and applications, not individual transport
  protocols."

I'm not sure what "ConEx represents" means here, but no matter which way I interpret it I have a hard time getting to the conclusion that this sentence makes. I would recommend that this sentence and the one that follows it focus on the implications of the abstract mechanism described in this document, rather than on what the IETF does or does not do.

= Section 4.4 =
"As long as the packets in a flow have uniform sizes, it does not
  matter whether the units of congestion are packets or bytes.
  However, if an application sends very irregular packet sizes, it may
  be necessary for the sender to mark multiple packets to avoid being
  in technical violation of an audit function measuring in bytes (see
  Section 4.6)."

This makes me wonder how the sender is supposed to know whether an audit function at any given point on the network is counting in bytes or in packets, or what happens if the same packet/sender encounters audit functions on two different networks (in a single path, or in a multi-homed sender scenario) that count using different units. The requirement in Section 4.6 that the encoding scheme specify its assumption about units isn't sufficient, because packets that use the scheme could encounter an audit function that makes the opposite assumption. Is this addressed somewhere?

[Ballot comment]
Thanks for your response and agreed changes per the SecDir review.
https://www.ietf.org/mail-archive/web/secdir/current/msg05057.html

The draft looks good, thanks for your work on it and the detail level for security requirements like the specific requirements to protect against several attacks that may lead to a DoS in section 3.2 Audit. 

I found the first paragraph of 5.4 helpful to better understand what was intended by the term audit and think it would have been good to have that understanding a little earlier in the draft.  I was looking for possible security concerns that don't apply once I read this definition.

[Ballot comment]
I submit that a good number of the references really are normative, in that understanding them is necessary in order to understand this document.  I'd like to see the authors sort that out, and make an appropriate split in the references, so readers can know which ones truly do just add extra detail (informative), and which provide necessary background (normative).  That said, I don't consider that important enough to this document to block on it, so this is a non-blocking comment.  Please consider doing this, but there is no need to respond to me about it.  Thanks.

IESG/Authors/WG Chairs:

IANA has reviewed draft-ietf-conex-abstract-mech-12, 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:  (Congestion Exposure (ConEx) Concepts, Abstract Mechanism and Requirements) to Informational RFC


The IESG has received a request from the Congestion Exposure WG (conex)
to consider the following document:
- 'Congestion Exposure (ConEx) Concepts, Abstract Mechanism and
  Requirements'
  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 2014-08-08. 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 an abstract mechanism by which senders inform
  the network about the congestion encountered by packets earlier in
  the same flow.  Today, network elements at any layer may signal
  congestion to the receiver by dropping packets or by ECN markings,
  and the receiver passes this information back to the sender in
  transport-layer feedback.  The mechanism described here enables the
  sender to also relay this congestion information back into the
  network in-band at the IP layer, such that the total amount of
  congestion from all elements on the path is revealed to all IP
  elements along the path, where it could, for example, be used to
  provide input to traffic management.  This mechanism is called
  congestion exposure or ConEx.  The companion document "ConEx Concepts
  and Use Cases" provides the entry-point to the set of ConEx
  documentation.




The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-conex-abstract-mech/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-conex-abstract-mech/ballot/


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

  http://datatracker.ietf.org/ipr/1922/

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)?

Informational

Why is this the proper type of RFC?

The document describe the CONEX mechanisms in a abstract way. Other RFCs produced in the WG will define the actual protocol and will be Experimental.

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:

  This document describes an abstract mechanism by which senders inform
  the network about the congestion encountered by packets earlier in
  the same flow.  Today, network elements at any layer may signal
  congestion to the receiver by dropping packets or by ECN markings,
  and the receiver passes this information back to the sender in
  transport-layer feedback.  The mechanism described here enables the
  sender to also relay this congestion information back into the
  network in-band at the IP layer, such that the total amount of
  congestion from all elements on the path is revealed to all IP
  elements along the path, where it could, for example, be used to
  provide input to traffic management.  This mechanism is called
  congestion exposure or ConEx.  The companion document "ConEx Concepts
  and Use Cases" provides the entry-point to the set of ConEx
  documentation.


Working Group Summary:

There were no special issues worth noting during the WG process.

Document Quality:

The document received several thorough reviews. It is worth noting the reviews from Mirja Kuehlewind and David Wagner.
Personnel:

Who is the Document Shepherd?

Marcelo Bagnulo

Who is the Responsible Area Director?

Martin Stiemerling

(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.

I reviewed the document and I believe it 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 concern, several reviews of the document have been done and a lot of effort have been invested by the editors of the document.

(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 reviews are required by the document.

(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, they have confirmed.

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

There has been an IPR disclosure for the document. See https://datatracker.ietf.org/ipr/1922/
This was announced on the CONEX WG ml and briefly discussed (mostly due to an error in the announcement).
The WG was ok to go along with this, given the licensing terms.

(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 was quite a bit of discussion in the WG and in the ml about this document, so I believe the consensus behind the document is strong.

(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 threats were received.

(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.

ID nits checked. The only nits that are detected are outdated references (i.e. there is newels version of referenced drafts). this will need to be fixed anyway before publication as it is likely that even newer versions will come up between now and the final publication date.

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

No special formal review criteria is 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?

The only normative reference is RFC 2119.

(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 downward 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.

The publication of this document ail not change the status of any RFC.

(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 does not include any IANA request.

(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.

No special checks are required.