Directional Airtime Metric Based on Packet Sequence Numbers for Optimized Link State Routing Version 2 (OLSRv2)
RFC 7779

This document was approved at the Dec/3.15 IESG Telechat pending an update to reflect the discussions with the SEC and ART ADs.  While all conversations should be addressed, the MITM topic is of special importance.

[Ballot comment]

- General: This seems mostly to be an abstract metric that could be
re-used e.g. in ROLL or HOMENET (if it's good:-) but with
OLSR-specific text and concepts mixed in here and there.  It'd have
been better were it possible to separate the abstract metric from
the OLSR-specifics to make the former easier to re-use later. It's
fine if determining if that would be useful is a part of the
experiment, but it might be good to mention it here.

- Section 6: In particular "fraction of the loss rate" isn't clear
to me, but maybe that's fine and it's known term of art to folks who
do metrics.

- Section 11: Wrt the MitM comments from other ADs - one possiblity
here might be to recommend that protocols making use of this metric
should be cognizant of, and include mitigtions for, MitM attacks of
this kind. (Just a suggestion, feel free to ignore if you prefer.)

- Thanks for handling the secdir review [1] - I think that all the
issues there were resolved, but do say if some still need a bit
more chatting.

  [1] https://www.ietf.org/mail-archive/web/secdir/current/msg06185.html

[Ballot comment]
I agree with Kathleen's "Close to a Discuss" on warning about MitM attacks. I'm fine with actually addressing the attacks being out of scope, as I believe Kathleen is.

[Ballot comment]
- section 1, last paragraph:
The first part of this paragraph sounds like justification for making this standards track. It would be useful to discuss why this is experimental.  Is there an expectation some version of this may be republished in the standards track in the future? Is there a need for deployment experience prior to standardization?

Editorial Comments:

- Abstract:
Please expand OLSRv2 on first mention in abstract. (In addition to the existing expansion in the body.)

- section 4, 1st paragraph:
s/metric/metrics

[Ballot comment]
This is just a comment as the text is mostly there, but I feel like it could be stated more clearly...

In the Security considerations section, the first part of the discussion could call out "Denial of Service" attacks explicitly in addition to the description that is included that describes altering traffic patterns.  I would recommend making this a distinct paragraph for readability.

The next part of the security considerations section (starts with the last sentence of the first paragraph) seems it could also be a result of the lack of integrity protections on this measurement technique.  It might help to state that first and that active attacks may result as a consequence, leaving in the active attacks you already describe and the solution already included starting with the second sentence of the second paragraph.  If that's not the case, please just let me know why.

How is warning about MiTM attacks out-of-scope?  It seems these are possible, and even mentioned with rogue routers.  Wouldn't it be easier to state that without session encryption, MiTM is a threat?  If this is acknowledged, then at least the consideration is there for the reader to understand.  Addressing the threat may be out-of-scope, but warning about it shouldn't be.  This last comment is much closer to a discuss, so I'd appreciate a response.

Thank you!

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

IANA has reviewed draft-ietf-manet-olsrv2-dat-metric-07.txt, 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: aretana@cisco.com, manet@ietf.org, draft-ietf-manet-olsrv2-dat-metric@ietf.org, bebemaster@gmail.com, manet-chairs@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Packet Sequence Number based directional airtime metric for OLSRv2) to Experimental RFC


The IESG has received a request from the Mobile Ad-hoc Networks WG
(manet) to consider the following document:
- 'Packet Sequence Number based directional airtime metric for OLSRv2'
  as Experimental 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 2015-11-23. 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 specifies an directional airtime link metric for usage
  in OLSRv2.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-manet-olsrv2-dat-metric/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-manet-olsrv2-dat-metric/ballot/


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

I sent these comments to the authors:

=====
Hi!

I just finished reading this draft.  Thank you for the background and history.

I identified some Major issues that should be easy to fix.  But in general I found the document relatively easy to read and understand.  Once you address the comments (and post an update, as needed) for the Major items I will start the IETF Last Call.

Thanks!

Alvaro.


Major:
What are the parameters of this experiment?  Being an Experimental document, there should be some guidance as to what type of information wants to be collected, what type of topologies should be used, etc..to eventually declare the experiment a success.  This information can be used later to change the track and (for example) use it to move the DAT into the Standards Track.

Section 9.2. (Requirements for using DAT metric in OLSRv2 implementations) 
What happens to packets that don't meet these requirements?  I'm assuming that they're just not used to calculate the DAT, is that true?  Is it ok if some packets on a link meet the requirements and others don't?
The INTERVAL_TIME TLV doesn't have to be in every HELLO (according to rfc6130), and Section 9.4 accounts for that already.  So it looks like that is not really a requirement.

There is some rfc2119 language in Section 9.3. (Link Loss Data Gathering) that is not clear.
"For each incoming [RFC5444] packet, additional processing SHOULD be carried out after the packet messages have been processed as specified in [RFC6130] and [RFC7181]."  Which additional processing?  Are you just referring to what is specified later in this section?  Please be specific.
"[RFC5444] packets without packet sequence number MUST NOT be processed in this way by this metric."  I'm guessing here you also are referring to what's specified in the rest of the section, right? 

Even though this document doesn't formally (because it is Experimental) Update rfc5444, rfc6130 and rfc7181, it would be a good idea to include a section (maybe around Section 5) that summarizes the changes/updates done here.


Minor:
In Section 2. (Terminology), "diff_seqno(new, old)" is defined.  However, Section 9.3 uses "seq_diff" instead.

Section 3. (Applicability Statement): the references to OLSRv2 seems to not be correct.

Section 6. (Protocol Parameters)
This section starts by talking about "two constants", and then listing "these constants", but the list actually has 4 parameters.  Section 7 also seems to talk about constants.  Should these two sections be merged into one??
s/DAT_MEMORY_LENGTH  - Queue length…within the queue are used to calculate the cost of the link./DAT_MEMORY_LENGTH  - Queue length…within the queue length are used to calculate the cost of the link.

In Section 6.1. (Recommended Values) the recommended value for DAT_REFRESH_INTERVAL is 1; the first paragraph says that "mobile networks might require shorter DAT_REFRESH_INTERVAL".  The only thing lower than 1 is 0; would that mean that in a mobile network the recommendation is to continuously recalculate the metric?

References:
RFC3626, RFC7182 and RFC7183 can be Informative.

Do you want to reference the appendixes (B, C and D) somewhere in the main text?


Nits:
Introduction: s/OLSR networks gathered since the publication of OLSR/OLSR networks gathered since its publication

The DLEP reference is out of date.

Section 4:
s/dijkstra/Dijkstra
"…already gathered link loss data…"  A reference to Section 9 would be nice.

Appendix A.
B.A.T.M.A.N. Reference?
"consists of 400 routers (around 600 routes)"  400 or 600?

Idnits identifies some line spacing issues, please take a look.
=====

(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?

Experimental.  The draft proposes a method of calculating a metric to be used in a standard protocol, RFC 7181 (in a standard way.) This experimental draft will allow OLSRv2 deployments with a metric defined by the IETF MANET group.  It enables easier interoperability tests between implementations and will also deliver a useful baseline to compare other metrics to.

(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 specifies an directional airtime link metric for usage in OLSRv2.  A major shortcoming of OLSR was the use of hop count as a routing metric for MANET networks, which can have highly variable and heterogeneous link properties.  OLSRv2 integrates the concept of link metrics directly into the core specification but the calculation and/or acquisition of this dimensionless additive link cost is not specified. 

This document describes a method for specifying this routing metric for OLSRv2, the Directional Airtime routing metric.  This metric is a successor of the ETX-derived OLSR.org routing metric used since 2004.  It takes both loss rate and the link speed into account to provide a more accurate picture of the links within the network.

Working Group Summary:
There were no working group issues with any specific points.  There was desire for slight differences in the definition of the metric but as this is an experimental draft it does not preclude other different metrics from being defined and used.

Document Quality:

There are at least 3 different independent implementations.  Most OLSRv2 implementation authors have either implemented this draft or at least voiced the desire to do so. The specification is clear but at parts the prose are a bit awkward.

Personnel:
Document Shepherd?  Justin Dean
Responsible Area Director? Alvaro Retana

(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 shepherd has read and implemented the draft and 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 concerns.
(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.

An English Language review would be helpful.

(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 issues.

(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?

No IPR issues.

(8) Has an IPR disclosure been filed that references this document? If so, summarize any WG discussion and conclusion regarding the IPR disclosures.
No IPR issues.

(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 broad moderate support for the document with a few individuals strongly in support of it.  There was no opposition.

(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

2.13.02 
/tmp/draft-ietf-manet-olsrv2-dat-metric-06.txt:
/tmp/draft-ietf-manet-olsrv2-dat-metric-06.txt(428): Line has weird
spacing: '...eceived  is a ...'
/tmp/draft-ietf-manet-olsrv2-dat-metric-06.txt(432): Line has weird
spacing: '...T_total  is a ...'
/tmp/draft-ietf-manet-olsrv2-dat-metric-06.txt(437): Line has weird
spacing: '...et_time  is th...'
/tmp/draft-ietf-manet-olsrv2-dat-metric-06.txt(440): Line has weird
spacing: '...nterval  is th...'
/tmp/draft-ietf-manet-olsrv2-dat-metric-06.txt(453): Line has weird
spacing: '...tervals  is th...'
/tmp/draft-ietf-manet-olsrv2-dat-metric-06.txt(457): Line has weird
spacing: '...bitrate  is th...'
/tmp/draft-ietf-manet-olsrv2-dat-metric-06.txt(460): Line has weird
spacing: '...t_seqno  is th...'

No boilerplate issues or nits found

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

N/A

(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.

This will not change the status of any other 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).

As this document uses code-points defined in OLSRv2 (RFC 7181) and does not require any OTA signaling it does not require additional allocation by 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.

N/A

(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.

N/A