Use Cases and Operational Experience with Multipath TCP
draft-ietf-mptcp-experience-07

[Ballot discuss]
This is a great document, thank you for writing it.

I have one small change request though (based on Dan Romascanu's Gen-ART review):

> Multipath TCP was standardized in [RFC6824]

Please change this to "specified" (RFC 6824 is experimental).

[Ballot comment]
I would also like to request that the authors look at Dan's other comments:

---

Summary: Ready with issues

A very useful and well written document, which gathers implementation
and deployment experience and expands the list of the Multipath TCP
Use Cases. A few minor issues described below, if addressed, could
improve the clarity and usability of the document.

Major issues:

Minor issues:

1. The 'Introduction' section starts with the statement:

Multipath TCP was standardized in [RFC6824] and five independent
  implementations have been developed.

Saying 'was standardized' seems misleading to me, as RFC 6824 is an
experimental RFC, so not even standards-track (this putting aside the
discussions whether RFCs are standards). Actually at no point this
document mentions that Multipath TCP is Experimental, this seems odd.

2. It would be useful to clarify the statement about the iOS
implementation of Multipath TCP in the Introduction by mentioning what
'single application' is referred.

However, this particular Multipath TCP implementation is currently only used to support a single application.'

3. I am questioning whether the 'Multipath TCP proxies' section really
belongs to the use cases or rather to operational experience. After
all it's about a strategy of deployment of Multipath TCP in cases
where clients and/or servers do not support Multipath TCP but the need
exists probably because of the combination of one or several other use
cases.

4. In section 3.5:

There have been suggestions from Multipath TCP users to modify the
  implementation to allow the client to use different destination ports
  to reach the server.  This suggestion seems mainly motivated by
  traffic shaping middleboxes that are used in some wireless networks.
  In networks where different shaping rates are associated to different
  destination port numbers, this could allow Multipath TCP to reach a
  higher performance.  As of this writing, we are not aware of any
  implementation of this kind of tweaking.

Beyond the potential problems described in the following paragraph, is
such a 'tweak' consistent with the protocol definition, or would it
need to cause changes in the protocol as defined now? A clear
recommendation seems to be needed here.

5. A more clear recommendation would be useful also in 3.8. It is not
clear here whether the segment size selection is a design or a tuning
issue that can/should be added to applications.


Nits/editorial comments:

1. Section 3.12 contains a timed statement 'As of September 2015 ...'
which should be updated or maybe edited to make it less
time-dependent.

2. It seems to me that [RFC6824] and [RFC6181] should be Normative
References as they describe the protocol extensions, and the initial
list of use cases which is expanded by this document. Without reading
these two documents, this one does not make too much sense.

[Ballot comment]
Thanks for this document.

- This document contains a couple of possible improvements.
I believe this important aspect of the draft should also be mentioned in the abstract.

- Just a thought (no need to reply):
On one side, section 3.1 speaks of "middlebox interference".
On the other side, this document via [I-D.lhwxz-hybrid-access-network-architecture] proposes just that: a new middlebox function.
This new middlebox might generate some interference for others.  Sarcasm warning: I guess that middleboxes are like children, we can only stand ours.
I wanted to make that point, in light of all the middlebox discussions these days, for example in the QUIC charter.

- Another thought (again no need to reply)
  "Since September
  2013, Multipath TCP is also supported on smartphones and tablets
  running iOS7 [IOS7].  There are likely hundreds of millions of
  Multipath TCP enabled devices.  However, this particular Multipath
  TCP implementation is currently only used to support a single
  application.  Unfortunately, there is no public information about the
  lessons learned from this large scale deployment."

Yes, this is really unfortunate.

Below is Qin Wu's OPS directorate review:
I think this document is well written and ready for publication. Here are a few editorial comments:

1.      Section 1, paragraph 2 mentions that three implementation are open sources. Which three of them are open sources? I think it includes apple MP-TCP, but it is not clear in the text.

2.      Section 2.2 paragraph 7 points out using REMOVE_ADDR option may cause operational problem, but I don’t see any discussion on this in the operation experience section, is this an open issue that needs to be addressed in the future or other document?

3.      Section 3.1 talks about the v0.87 Multipath TCP implementation What does V0.87 stands for? Version number? is there any reference to it?

4.      Section 3.2

s/the the default congestion control/ the default congestion control

5.      Section 3.2 last paragraph said that Reports from some users indicate that they seem to favor OLIA. It looks this statement is groundless statement.

6.      Section 3.9

s/ returned to the DNS query/return in response to the DNS query

7.      Section 3.10 said:

“

A better approach would probably be to try a few attempts on

the WiFi interface and then try to use the second interface for the

initial subflow as well.

”

When trying to use second interface for initial subflow? A few attempts on the WIFI interface fails?

8.      Section 3.2

s/accomodate/accommodate

[Ballot comment]
Should this text

  The FTP interference is expected and due to
  Application Level Gateways running home routers.
 
be "running in home routers"? I'm not sure how to parse the sentence otherwise.

When reading this text

  This may be
  excessive in some environments, in particular when the client and/or
  the server have a large number of interfaces.
 
I am reminded that multiple IP addresses per interface are common in IPv6 and dual stack deployments. That would make the situation worse, wouldn't it? If so, would that be worth saying?

[Ballot comment]
I support Stephen's comment, and have a few minor comments of my own (none of which are showstoppers):

-1, first paragraph: I'm not sure we should describe an experimental RFC as "standardized".

-1, mention of iOS7: Is this really limited to iOS7 and not future versions? Would it make since to say that "Since September 2013...is also supported ... iOS"? (i.e. without the version?)  (Noting that iOS10 released this week...)

- 2.2, paragraph 9: Figure 1 just shows a generic 2 path connection. It doesn't seem to "summarize" the described scenario.

-2.2, 2nd paragraph after figure 1: I'm pretty sure there are in fact real applications that transfer bulk data. Do you mean to say that "Some [or even many or most] real applications do not..."

[Ballot comment]

I was a bit sad that there was no reporting of
experiences with the security aspects of MPTCP.  Have
we really learned nothing worth saying about that?
Have we really seen no attacks on, or tailored to,
MPTCP? It seems odd that the answer to both questions
is "no."

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

IANA has reviewed draft-ietf-mptcp-experience-06.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.

Thank you,

Sabrina Tanamal
IANA Specialist
ICANN

The following Last Call announcement was sent out:

From: The IESG
To: "IETF-Announce"
CC: draft-ietf-mptcp-experience@ietf.org, mptcp-chairs@ietf.org, multipathtcp@ietf.org, philip.eardley@bt.com, ietf@kuehlewind.net, "Philip Eardley" , olivier.bonaventure@uclouvain.be
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Use Cases and Operational Experience with Multipath TCP) to Informational RFC


The IESG has received a request from the Multipath TCP WG (mptcp) to
consider the following document:
- 'Use Cases and Operational Experience with Multipath TCP'
  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 2016-09-13. 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 discusses both use cases and operational experience
  with Multipath TCP in real world networks.  It lists several
  prominent use cases for which Multipath TCP has been considered and
  is being used.  It also gives insight to some heuristics and
  decisions that have helped to realize these use cases.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-mptcp-experience/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-mptcp-experience/ballot/


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

Document Writeup for Working Group Documents

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?
Informational – the document provides information about use cases and operational experiences of using multipath TCP

(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 discusses both use cases and operational experience with Multipath TCP in real world networks.  It lists several prominent use cases for which Multipath TCP has been considered and is being used.  It also gives insight to some heuristics and decisions that have helped to realize these use cases.
Working Group Summary:
The WG consensus is good.
Document Quality:
The document has been written by several of the people who have implemented the MPTCP protocol and who are intimately involved in its deployment. The document is very informative.
Personnel:
The Document Shepherd is Philip Eardley. The Responsible Area Director is Mirja Kühlewind.

(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 has been reviewed by the Shepherd. Various nits were corrected, including the addition of IANA and Security Considerations sections.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?
No.

(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.
No.

(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.

(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?
Good consensus

(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.
ID nits:
  == Line 1171 has weird spacing: '...o Tokyo  on th...'
Comment: this is a missing ‘:’
  -- The document date (July 08, 2016) is 5 days in the past.  Is this intentional?
Comment: Yes
  == Outdated reference: draft-ietf-dnsop-edns-client-subnet has been published as RFC 7871

(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 (all informative)

(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?
Not applicable

(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).
Reviewed – I agree there are no IANA considerations

(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.
Not applicable

(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.
Not applicable