Stream Schedulers and User Message Interleaving for the Stream Control Transmission Protocol
draft-ietf-tsvwg-sctp-ndata-13

[Ballot comment]
I looked at the references for security considerations, [RFC4960] and [RFC6458], and don't see an explicit mention of fragmentation overlap and in my skim, didn't see that it was covered for reassembly as a warning.  Does this need to be added?  If not, can you explain how it is covered?

[Ballot comment]
I looked at the references for security considerations, [RFC4960] and [RFC6458], and don't see an explicit mention of fragmentation overlap and in my skim, didn't see that it was covered for reassembly as a warning.  Does this need to be added?  If not, can you explain how it is covered for each level?

[Ballot comment]
I wish this had been around back when we were figuring out how to share connections in MSRP.

Otherwise, just a couple of editorial comments:

- Abstract: "Multiple ways for performing
  this selection, called stream schedulers, are defined. "
I assume you mean that they are defined in this document rather than in previously existing documents, but it seems ambiguous.

- 2.1: "The sender uses two counters for
      each outgoing stream, one for ordered messages, one for unordered
      messages.  All counters are independent and initially 0."

s/ all / both  ; unless this rule is intended to apply to more counters than the ones mentioned in the previous sentence.

[Ballot comment]
Mostly editorial comments:
1) Why, after all, is SSN renamed to MID? I understand that the MID was extended to 32 bit and that the name might be more appropriate but I still find it confusing given both fields have the same semantics. Maybe it would help to point this out more explicitly in the document.

2) It could be helpful for the reader to also name the I and the U bits in section 2.1; especially the U bit could be referenced when MID is explained.

3) Should there maybe be a recommendation that re-assotiating without interleaving support could be tried if a ABORT message is received. I guess that failure case could occur if the negation was altered in the network and one end thinks it support interleaving but the other not...?

4) Related to my first point: I guess you only need a new I-FORWARD-TSN chunk because you use MID instead of SSN. This seem to me that you just took the opportunity to make this change with this extension but then it should maybe be the spell out as a 'separate' change/improvement in the intro.

5) Really a nit but hard to read otherwise; you really need to use a comma here (sec 1.1):
OLD
"If I-DATA support has been negotiated for an association
  I-DATA chunks are used for all user-messages."
NEW
"If I-DATA support has been negotiated for an association,
  I-DATA chunks are used for all user-messages.“

[Ballot comment]
TECHNICAL
I'm not sure I am following the rules about interleaving multiple
messages in the same flight.

  The sender MUST NOT fragment more than one user message in any given
  stream at any time.  At any time, a sender MAY fragment multiple user
  messages, each of them on different streams.

So, say I have one stream and the application sends M1 and M2 and both
need to be fragmented, so I have M1a, M1b and M2a and M2b. Does this
mean that I can't send M2a until M1{a,b} has been acknowledged?
If so what's the need for that requirement? It seems like you could
use MID to reassemble correctly. And given this requirement, why do
you need MID?


Because fragementation is indicated by index, not range,
what happens if you have to reduce MTU? So, say I have a message of
size 2K which I fragment into 1K/1K and then I have to decrease
my MTU to 512 bytes?


EDITORIAL
I think it would be helpful to indicate that B has to be
set for the first chunk in S 2.1. Or perhaps move the overview of
how the sender behaves in S 2.2.2 up in the document?

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

The IANA Services Operator has completed its review of draft-ietf-tsvwg-sctp-ndata-12. If any part of this review is inaccurate, please let us know.

The IANA Services Operator understands that, upon approval of this document, there are three actions which we must complete.

First, in the Chunk Types registry on the Stream Control Transmission Protocol (SCTP) Parameters registry page located at:

https://www.iana.org/assignments/sctp-parameters/

a new Chunk Type will be registered as follows:

ID Value: [ TBD-at-registration ]
Chunk Type: Payload Data Supporting Interleaving [I-DATA]
Reference: [ RFC-to-be ]

We note that the authors have suggested 64 for this ID Value and the value must come from the pool of chunks with the upper two bits set to "01."

Second, also in the Chunk Types registry on the Stream Control Transmission Protocol (SCTP) Parameters registry page located at:

https://www.iana.org/assignments/sctp-parameters/

a new Chunk Type will be registered as follows:

ID Value: [ TBD-at-registration ]
Chunk Type: I-FORWARD-TSN
Reference: [ RFC-to-be ]

We note that the authors have suggested 194 for this ID Value and the value must come from the pool of chunks with the upper two bits set to "11."

Third, a new subregistry for the I-DATA Chunk Flags will be created under the Chunk Flags registry also on the Stream Control Transmission Protocol (SCTP) Parameters registry page located at:

https://www.iana.org/assignments/sctp-parameters/

I-DATA Chunk Flags

+------------------+-----------------+---------------+
| Chunk Flag Value | Chunk Flag Name | Reference |
+------------------+-----------------+---------------+
| 0x01 | E bit | [ RFC-to-be ] |
| 0x02 | B bit | [ RFC-to-be ] |
| 0x04 | U bit | [ RFC-to-be ] |
| 0x08 | I bit | [ RFC-to-be ] |
| 0x10 | Unassigned | |
| 0x20 | Unassigned | |
| 0x40 | Unassigned | |
| 0x80 | Unassigned | |
+------------------+-----------------+---------------+

The IANA Services Operator understands that these three actions are the only ones required to be completed upon approval of this document.

Note:  The actions requested in this document will not be completed until the document has been approved for publication as an RFC. This message is only to confirm what actions will be performed.


Thank you,

Sabrina Tanamal
IANA Services Specialist

The following Last Call announcement was sent out (ends 2017-08-25):

From: The IESG
To: IETF-Announce
CC: gorry@erg.abdn.ac.uk, tsvwg@ietf.org, spencerdawkins.ietf@gmail.com, Gorry Fairhurst , draft-ietf-tsvwg-sctp-ndata@ietf.org, tsvwg-chairs@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Stream Schedulers and User Message Interleaving for the Stream Control Transmission Protocol) to Proposed Standard


The IESG has received a request from the Transport Area Working Group WG
(tsvwg) to consider the following document: - 'Stream Schedulers and User
Message Interleaving for the Stream Control
  Transmission Protocol'
  as 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 2017-08-25. 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


  The Stream Control Transmission Protocol (SCTP) is a message oriented
  transport protocol supporting arbitrarily large user messages.  This
  document adds a new chunk to SCTP for carrying payload data.  This
  allows a sender to interleave different user messages that would
  otherwise result in head of line blocking at the sender.  The
  interleaving of user messages is required for WebRTC Datachannels.

  Whenever an SCTP sender is allowed to send user data, it may choose
  from multiple outgoing SCTP streams.  Multiple ways for performing
  this selection, called stream schedulers, are defined.  A stream
  scheduler can choose to either implement, or not implement, user
  message interleaving.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-ndata/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-ndata/ballot/


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

Shepherd wiretap for draft-ietf-tsvwg-sctp-ndata-11

As required by RFC 4858, this is the current template for the Document Shepherd Write-Up.

(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?

Standards Track, PS.

(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:

  The Stream Control Transmission Protocol (SCTP) is a message oriented
  transport protocol supporting arbitrarily large user messages.  This
  document adds a new chunk to SCTP for carrying payload data.  This
  allows a sender to interleave different user messages that would
  otherwise result in head of line blocking at the sender.

  Whenever an SCTP sender is allowed to send user data, it may choose
  from multiple outgoing SCTP streams.  Multiple ways for performing
  this selection, called stream schedulers, are defined.  A stream
  scheduler can choose to either implement, or not implement, user
  message interleaving.

  In line with other SCTP specifications, this document includes an informational  appendix describing and API to the mechanisms.

Working Group Summary:

The document has received feedback from the WG.

Document Quality:

This document is one of several relating to WebRTC Datachannels, and has received inputs from other related WGs.

Personnel:

Who is the Document Shepherd?  Gorry Fairhurst

Who is the Responsible Area Director? Spencer Dawkins

(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.

This document is ready.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?

No. This draft has been reviewed many times.

The FreeBSD kernel implementation and the userland stack usrsctp (which shares most of the code) both support sending and receiving of I-DATA chunks. An implementation of interleaving schedulers is planned in the timeframe of IETF 99.

(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.

None.

(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?

The authors confirm they know of no IPR.

(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 known.

(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?

The document has been presented to the WG and there was consensus on the document during WGLC. Minor issues were raised, and changes have been incorporated in this revision of the ID.

(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.

None.

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

Not required.

(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.

None.

(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).

This memo includes a request to IANA, see the IANA considerations. The request seems to be consistent with other SCTP assignments.

(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.

This memo does not include a request for a new registry to IANA.

(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.

None.

Shepherd wiretap for draft-ietf-tsvwg-sctp-ndata-11

As required by RFC 4858, this is the current template for the Document Shepherd Write-Up.

(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?

Standards Track, PS.

(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:

  The Stream Control Transmission Protocol (SCTP) is a message oriented
  transport protocol supporting arbitrarily large user messages.  This
  document adds a new chunk to SCTP for carrying payload data.  This
  allows a sender to interleave different user messages that would
  otherwise result in head of line blocking at the sender.

  Whenever an SCTP sender is allowed to send user data, it may choose
  from multiple outgoing SCTP streams.  Multiple ways for performing
  this selection, called stream schedulers, are defined.  A stream
  scheduler can choose to either implement, or not implement, user
  message interleaving.

  In line with other SCTP specifications, this document includes an informational  appendix describing and API to the mechanisms.

Working Group Summary:

The document has received feedback from the WG. The FreeBSD kernel implementation and the userland stack usrsctp (which shares most of the code) both support sending and receiving of I-DATA chunks. An implementation of interleaving schedulers is planned in the timeframe of IETF 99.

Document Quality:

This document is one of several relating to WebRTC Datachannels, and has received inputs from other related WGs.

Personnel:

Who is the Document Shepherd?  Gorry Fairhurst

Who is the Responsible Area Director? Spencer Dawkins

(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.

This document is ready.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?

No. This draft has been reviewed many times.

(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.

None.

(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?

The authors confirm they know of no IPR.

(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 known.

(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?

The document has been presented to the WG and there was consensus on the document during WGLC. Minor issues were raised, and changes have been incorporated in this revision of the ID.

(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.

None.

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

Not required.

(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.

None.

(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).

This memo includes a request to IANA, see the IANA considerations. The request seems to be consistent with other SCTP assignments.

(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.

This memo does not include a request for a new registry to IANA.

(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.

None.

Comments have been received form members of the TSVWG list. I counted  5 sets of comments - ranging from editorial to questions asking for clarification. The authors are now requested to submit a revised ID to address the noted issues.

The WG will no await an updated draft.  If there are issues that are not addressed in the revised draft - could the authors please clearly identify these and explain why the issue was not addressed.

This email announces a TSVWG Working Group Last Call (WGLC) on:

            Stream Schedulers and User Message Interleaving for SCTP
            draft-ietf-tsvwg-sctp-ndata
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-ndata

This WGLC will last for about 2 weeks weeks.

Comments should be sent to the tsvwg@ietf.org list, although purely
editorial comments may be sent directly to the authors. Please cc: the
WG chairs at tsvwg-chairs@ietf.org  if you would like the chairs to track
such editorial comments as part of the WGLC process.

No IPR disclosures have been submitted directly on draft-ietf-tsvwg-sctp-ndata.

Thanks,
Gorry
(TSVWG Co-Chair)