Raptor Forward Error Correction Scheme for Object Delivery
draft-ietf-rmt-bb-fec-raptor-object-09

[Ballot comment]
Although it can be inferred from the title, it would be better to expand
"FEC" on first use in the abstract.

This document would benefit from a walk through of the encode/decode
process using some real sample data and showing the intermediate values.

I found the description of the algorithm with 1-2 letter variables
difficult to follow and eventually gave up.  I suspect I'd have better
luck following pseudo-code with more descriptive variable names.  It's
quite possible the target for this specification is a very small group
of subject matter experts in which case I'm not in the target market.
But if the target market is people who are curious about FEC and have
a BS in mathematics, then this is too opaque to reach much of that
market.

Editorial Nits:
>  block of a object and the value of T' may not necessarily be the same
a -> an

IANA Last call Comments:

Upon approval of this document, the IANA will make the
following assignments in the "Reliable Mutlicast Transport (RMT)
FEC Encoding IDs and FEC Instance IDs" registry located at

http://www.iana.org/assignments/rmt-fec-parameters

sub-registry "Fully-Specified FEC schemes"

Value Description Reference
----- ------------------------------------------------- ---------
1 Raptor
[RFC-rmt-bb-fec-raptor-object-08]

We understand the above to be the only IANA Action for this
document.

PROTO Write-up

(1.a) Who is the Document Shepherd for this document? Has the
Document Shepherd personally reviewed this version of the
document and, in particular, does he or she believe this
version is ready for forwarding to the IESG for publication?

Document Shepherd is Lorenzo Vicisano, who has personally
reviewed this version of the document and believes it is ready
for forwarding to the IESG for publication.

(1.b) Has the document had adequate review both from key WG members
and from key non-WG members? Does the Document Shepherd have
any concerns about the depth or breadth of the reviews that
have been performed?

The document had adequate review both from key WG members
and from key non-WG members. The content of this document was also
adopted in the following independent standards:

- 3GPP Multimedia Broadcast Multicast Service - Protocols and Codecs
(TS26.346)
- DVB IP Datacast over DVB-H: Content Delivery Protocols (CDP) -
(DVB Blue Book A101, ETSI TS 102 472)

The relevant standardization bodies did independently reviewed Raptor.

(1.c) Does the Document Shepherd have concerns that the document
needs more review from a particular or broader perspective,
e.g., security, operational complexity, someone familiar with
AAA, internationalization or XML?

No additional reviews needed.

(1.d) Does the Document Shepherd have any specific concerns or
issues 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. Has an IPR disclosure related to this document
been filed? If so, please include a reference to the
disclosure and summarize the WG discussion and conclusion on
this issue.

An IPR disclosure related to this document was filed by Digital
Fountain and updated three time, see link below.
https://datatracker.ietf.org/public/ipr_search.cgi?option=document_search&id_document_tag=12920

The RMT WG discussed this matter concluding that it wished to publish
this document nevertheless, as this represent valuable technology.
This specific FEC code is one of multiple alternative that can be used to
implement the RMT higher-level protocols, as such the possible IPR
covering this does not preclude the unencumbered implementation of the
RMT Protocols.

Please see relevant WG discussion on the WG mailing list archive at
http://www1.ietf.org/mail-archive/web/rmt/current/msg00717.html
and followups.

(1.e) 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?

This document represent a solid consensus of the RMT WG.

(1.f) 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
entered into the ID Tracker.)

No notable discontent, except for the IPR discussion, see point (1.d).

(1.g) Has the Document Shepherd personally verified that the
document satisfies all ID nits? (See
http://www.ietf.org/ID-Checklist.html and
http://tools.ietf.org/tools/idnits/). Boilerplate checks are
not enough; this check needs to be thorough. Has the document
met all formal review criteria it needs to, such as the MIB
Doctor, media type and URI type reviews?

The Document Shepherd has personally verified that the document
satisfies all ID nits.

(1.h) Has the document split its references into normative and
informative? 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
strategy for their completion? Are there normative references
that are downward references, as described in [RFC3967]? If
so, list these downward references to support the Area
Director in the Last Call procedure for them [RFC3967].

The document splits its references into normative and
informative. Of the normative references, one is in "BCP" state,
the other is being submitted to the IESG for its approval.
No Downward References.

(1.i) Has the Document Shepherd verified that the document IANA
consideration section exists and is consistent with the body
of the document? If the document specifies protocol
extensions, are reservations requested in appropriate IANA
registries? Are the IANA registries clearly identified? If
the document creates a new registry, does it define the
proposed initial contents of the registry and an allocation
procedure for future registrations? Does it suggest a
reasonable name for the new registry? See [RFC2434]. If the
document describes an Expert Review process has Shepherd
conferred with the Responsible Area Director so that the IESG
can appoint the needed Expert during the IESG Evaluation?

The IANA consideration section exists, it is consistent with the rest
of the document and is consistent with the registration guidelines
specified in draft-ietf-rmt-fec-bb-revised. No new registry is
defined. No Expert Review Process is necessary for the IANA assignments
requested by this document.

(1.j) Has the Document Shepherd verified that sections of the
document that are written in a formal language, such as XML
code, BNF rules, MIB definitions, etc., validate correctly in
an automated checker?

The documents contains no section written in formal language.

(1.k) 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
Relevant content can frequently be found in the abstract
and/or introduction of the document. If not, this may be
an indication that there are deficiencies in the abstract
or introduction.

Working Group Summary
Was there anything in WG process that is worth noting? For
example, was there controversy about particular points or
were there decisions where the consensus was particularly
rough?

Document Quality
Are there existing implementations of the protocol? Have a
significant number of vendors indicated their plan to
implement the specification? Are there any reviewers that
merit special mention as having done a thorough review,
e.g., one that resulted in important changes or a
conclusion that the document had no substantive issues? If
there was a MIB Doctor, Media Type or other expert review,
what was its course (briefly)? In the case of a Media Type
review, on what date was the request posted?

Personnel
Who is the Document Shepherd for this document? Who is the
Responsible Area Director?


Document Announcement Write-Up follows.

Technical Summary

This document is an optional Building Block usable to fully define
an RMT Transport Protocol. It fully-specifies a Forward Error
Correction Code, called "Raptor", within the guidelines of
draft-ietf-rmt-fec-bb-revised. It also specifies procedures and
packet-header fields, as required by draft-ietf-rmt-fec-bb-revised.

The combination of this document and draft-ietf-rmt-fec-bb-revised
allows the implementation of an interoperable Forward Error Correction
scheme usable in the context of an RMT transport protocol (e.g.
LCT/ALC or NORM).

Raptor is a fountain code, i.e., as many encoding symbols
as needed can be generated by the encoder on-the-fly from the
source symbols of a source block of data. The decoder is able to
recover the source block from any set of encoding symbols only
slightly more in number than the number of source symbols.

The Raptor code described here is a systematic code, meaning that all
the source symbols are among the encoding symbols that can be generated.

Working Group Summary

There is consensus in the WG to publish these documents.

Document Quality

The following independent standardization bodies have adopted the
Raptor specification in a form functionally equal to
draft-ietf-rmt-bb-fec-raptor-object-07:

- 3GPP Multimedia Broadcast Multicast Service - Protocols and
Codecs (TS26.346)
- DVB IP Datacast over DVB-H: Content Delivery Protocols (CDP) -
(DVB Blue Book A101, ETSI TS 102 472)

Lorenzo Vicisano is the Document Shepherd.
Magnus Westerlund is the Responsible Area Director.