A Conservative Loss Recovery Algorithm Based on Selective Acknowledgment (SACK) for TCP
draft-ietf-tcpm-3517bis-02

[Ballot comment]
I have no objection to the publication of this document.

One comment from Chris LILJENSTOLPE, part of the OPS-Directorate review.
I wish the authors had selected some other state variable name other than DupAck for the multiple SACK counter.  While it is well described in the draft, on first read it is really not a Duplicate ACK counter, but a multiple SACK counter (number of SACKs between covering ACKs).  While useful, it would have been more intuitive to call it MultSack or some such.  I do not propose editing the draft just for this purpose, but if another version of the draft is required, it may make the digestion of the material a little easier.

I leave up to you to act on his feedback.

Regards, Benoit.

IESG:

IANA has reviewed draft-ietf-tcpm-3517bis-02.txt, which is currently
in Last Call, and has the following comments:

We understand that this document doesn't require any IANA actions.

[Ballot comment]

"Pipe" definition says "The algorithm" is often
referred to as the pipe alg. That's a little unclear, maybe
better to say "The algorithm defined here...." and if
that is the case, to also put that in the abstract
and intro just to make it easier for someone who does
call it that to find the RFC.

[Ballot comment]

  The Gen-ART Review by Ben Campbell on 4-Apr-2012 suggests some
  improvements.  Please consider them.  The review can be found here:
  http://www.ietf.org/mail-archive/web/gen-art/current/msg07319.html

[Ballot comment]
I have no objection to the publication of this document.Just a couple of nits.

---

Isn't [PF01] rather old to be cited as "evidence that hosts are not
using the SACK information when making retransmission and congestion
control decisions"?

I guess this was good evidence when 3517 was first written, but maybe a
different form of words is called for now? Perhapswe don't even need
the evidence to motivte this work since it is now established.

---

Section 1

  A
  summary of the changes between this document and [RFC3517] can be
  found in Section 9.

Pardon my pedantry, but the changes are between 3517 and this document.

[Ballot comment]
Section 7 talks about the effectiveness of this approach when paired with TCP Reno, but I do not see any discussion of possible interactions with other TCP congestion control algorithms.  Has this re-transmission algorithm been tested with other congestion control algorithms?

[Ballot comment]
This seems a good, clear document.  Thanks for a thought-out Security Considerations section, as well.

I have one question, as a non-expert on this topic:
All four functions in section 4 are "SHOULD implement."  Can a meaningful implementation really be done if NONE of them are included?  If so, fine.  If not, maybe a few more words in the first paragraph would be useful, explaining under what conditions it's important to include them or makes sense to leave them out.

[Ballot comment]
An editorial:
It it is relative short document, but recents RFCs seems all to have a table of contents, which is missing in this draft.

State changed to In Last Call from Last Call Requested

The following Last Call Announcement was sent out:

From: The IESG

To: IETF-Announce

CC:

Reply-To: ietf@ietf.org

Subject: Last Call:  (A Conservative Selective Acknowledgment (SACK)-based Loss Recovery Algorithm for TCP) to Proposed Standard





The IESG has received a request from the TCP Maintenance and Minor

Extensions WG (tcpm) to consider the following document:

- 'A Conservative Selective Acknowledgment (SACK)-based Loss Recovery

  Algorithm for TCP'

  as a Proposed Standard



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 2012-04-11. 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 presents a conservative loss recovery algorithm for TCP

  that is based on the use of the selective acknowledgment (SACK) TCP

  option.  The algorithm presented in this document conforms to the

  spirit of the current congestion control specification (RFC 5681),

  but allows TCP senders to recover more effectively when multiple

  segments are lost from a single flight of data.









The file can be obtained via

http://datatracker.ietf.org/doc/draft-ietf-tcpm-3517bis/



IESG discussion can be tracked via

http://datatracker.ietf.org/doc/draft-ietf-tcpm-3517bis/ballot/





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

(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?

This document is requested to be published as Proposed
Standard. It is an update to an existing Proposed Standard RFC
3517. The intended status is NOT indicated on the title page
of the current version of document.

(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 a loss recovery algorithm based on the
use of TCP SACK option that conforms to the current TCP
congestion control requirements. It is a revision of Proposed
Standard RFC 3517, to provide clarifications and certain
performance enhancements to the earlier specified algorithm.

Working Group Summary

The document was accepted for publication by the TCPM working
group by clear consensus. The working group has extensively
reviewed the earlier versions of the document, and the result
represents the working group consensus. During the working
group last call, there were no requests for changes and only
comments were supportive of publication.

Document Quality

The document has employed the long-standing experience of
various people working closely with simulated and native TCP
SACK implementations. The current TCP SACK implementations are
believed to apply closely similar algorithm than what
described in this document, even though there may be
implementation-specific variations.

Personnel

Document Shepherd is Pasi Sarolahti .
Responsible Area Director is Wesley Eddy .

(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 Shepherd has reviewed the latest version of the
document and thinks the document is ready for publication
without further changes (apart from nits described below).

(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.

There are no concerns with the current version of the
document.

(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 IPR disclosures have been filed for this document, or its
predecessor RFC 3517.

(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?

Considering the past discussions and a succesful working group
last call, the shepherd's view is that this document
represents a strong WG 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.

* The title page is missing the intended status
* The document is missing IANA Considerations section (it has
no considerations, but the section should be included
nevertheless)
* According to idnits, there are a few instances of too long
lines and control characters
* Two references [RFC2018] and [RFC3042] are not referred to
from text

These nits should be straightforward to fix before the final
publication.

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

No formal reviews are required for this document.

(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 document is a revision of RFC 3517, and intended to
replace the earlier RFC, as implied by the draft name
(draft-ietf-tcpm-3517bis). This has not been otherwise
explicitly indicated on the title page, abstract, or
introduction, but the purpose is assumed to be understood by
the TCPM participants.

(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 have any IANA considerations, and is
currently missing the IANA considerations section.

(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 new IANA registries are required.

(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.

There are no sections that would require formal validation.