I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.
Please resolve these comments along with any other Last Call comments
you may receive.
Document: draft-ietf-rmt-bb-fec-raptorq-04
RaptorQ Forward Error Correction Scheme for Object Delivery
Reviewer: Joel M. Halpern
Review Date: 27-January-2011
IETF LC End Date: 09-Feb-2011
IESG Telechat date: N/A
Summary: This document is ready for publicaiton as a Proposed Standard.
Note: The reviewer did not attempt to verify the actual FEC behaviors,
but did focus on whether he believed an implementor could follow the
instructions to implement the algorithm. The comments below should be
considered if the document is revised.
Major issues: None
Minor issues:
It would probably be helpful in section 3.2.3 if there was some comment
as to why the number of source blocks is a 12 bit field when the last
paragraph of 3.2.2 says that the number of source blocks is limited to 256.
The order of presentation of material in section 5.3 is somewhat
confusing. Rather than changing it however, I think it woudl suffice if
a forward reference, in the text early in 5.3.3.3 is added, saying that
the algorithm describes here assumes that the C symobls have been
calculated according to the constraints in section 5.3.3.4. (The
challenge appears to be a matter of providing sufficient clarity without
over-constraining implementors.)
In describing the "First Phase" algorithm in section 5.4.2.2, the
chosing and arranging step seems to ensure that the first row of V has a
1 in the first column of V. Confusingly, the text then refers to the
chosen row having an entry alpha in the first column of V. It may be
that I misread the steps (in which case we should check if clarification
is needed), it may be that alpha is indeed always 1, in which case we
should say so, or it may be that the "ones" in the earlier selection
criteria is merely supposed to be "non-zeros".
Nits/editorial comments:
In 4.4.1.2 when defining the symbols IL, IS, JL, and JS, the
formula for JL gets split across a line boundary. It is very easy for a
reader to miss a piece, and get the completely wrong formula. (The
split causes the bind to invert the operator priority, if it does not
completely miss the extra operation.)
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