Subject: Luby Comments on [Rmt] WG Last Call draft-ietf-rmt-flute-02.txt

From: "Michael Luby" <[email-masked]>
Date: Fri, 10 Oct 2003 18:32:20 -0700

RMTers,
Here are some comments on draft-ietf-rmt-flute-02.txt.  Sorry I didn't make
these before WG last call (this apology is for you Toni), but none of them
are earth shattering and mostly just rewording/making it a bit clearer.
Mike

Comments on FLUTE 02

(1) Section 3, paragraph 3, change "As an example, let us consider a file
referred by ..." to "As an example, let us consider a 5200 byte file
referred to by ..."
(2) Section 3, third to last item in bulleted list: Change "In the above
example (imaginary): '5200' " to "In the above example: '5200' ".
(3) Section 3.1, second item in bulleted list: Change " 'File Deliver Table
Instance (section 3.2)' " to " 'File Deliver Table Instance' (section 3.2)."
(4) Section 3.1, third item in bulleted list: Change "... is reserved for
delivery of File Deliver Table " to "... is reserved for delivery of File
Deliver Table Instances. "
(5) Section 3.2, "Location of file" bullet should probably be changed to
"URL of file".
(6) Section 3.2, It seems that "size of file" should be listed under the
attributes related to the delivery of file, and perhaps also mentioned in
the attributes realted to the file itself as being relevant there, i.e., it
is an attribute relevant to both categories (and it would be good to list
this as an example to take away the impression that these are mutually
exclusive categories).
(7) Section 3.2, the sentence "Some of these attributes are mandatory, ..."
is confusing and vague.  Perhaps something like "Some of these attributes
MUST be included in the file description entry for a file, others are
optional, as defined in ..."
(8) Section 3.2, the paragraph just after the sentence mentioned in (7) is
confusing.  Perhaps it can be rewritten as follows: "Logically, the FDT is a
set of file description entries for files to be delivered in the session.
Each file description entry must include the TOI for the file that it
describes and the URL indicating the location of the file.  The TOI is
included in each ALC/LCT data packet during the delivery of the file, and
thus the TOI carried in the file description entry is how the receiver
determines which ALC/LCT data packets contain information about which file.
Each file description entry may also contain one or more descriptors that
map the above-mentioned attributes to the file."
(9) Section 3.2, the paragraph just after the paragraph mentioned in (8),
second sentence: Change "The FDT SHOULD provide a mapping for every TOI
appearing within the session." to "The FDT SHOULD provide a file description
entry mapped to a TOI for each file appearing within the session."
(10) Section 3.4, first sentence of second paragraph: Change "... and
finally the FDT Instance Payload which contains ..." to "... and finally the
Encoding Symbols for the FDT Instance Payload which contains ...".
(11) Section 3.4, Figure 1, This shows a UDP header proceeding the remainder
of the packet.  Perhaps it should be mentioned somewhere that, as defined in
[3], all ALC/LCT packets are sent using UDP.
(12) Section 3.4, Figure 1, replace "Default LCT header" with "Default LCT
header (with TOI = 0)".
(13) Section 5.1.2.1:   The language describing what the Source Block Length
means should be tightened up.  Suggested language:

Full-Sized Source Block Length, 32 bits

The number of source symbols in a full-sized source block, where the length
of each source symbol is the Encoding Symbol Length.  In this EXT_FTI
specification, it is assumed that there is an algorithm known to both sender
and receivers for determining the size of all source blocks within the file
identified by the TOI (or within the FDT Instance identified by the TOI and
the FDT Instance ID).  The exact specification of this algorithm is outside
the scope of this document.  However, this algorithm MUST adhere to the
following:
	(a) The length of each source block MUST be at most the Full-Sized Source
Block Length.
	(b) The length of all but the last source block MUST be a multiple of the
Encoding Symbol length. (The last source block is not a multiple of the
Encoding Symbol Length if the file length is not a multiple of the Encoding
Symbol Length.)
	(c) The length of all but the last source symbol of the last source block
MUST be the Encoding Symbol Length. (The last source symbol of the last
source block is truncated if the file length is not a multiple of the
Encoding Symbol Length.)
	(d) If a file consists of many source blocks then the length of most source
blocks SHOULD be equal to the Full-Sized Source Block Length.
	(e) All source blocks SHOULD be at least half the Full-Sized Source Block
Length.
	(f) The algorithm MUST depend only on information known to both the sender
and receivers, i.e., generally it is based on the file length (or FDT
Instance length), the Full-Sized Source Block Length and the Encoding Symbol
Length.

(14) In section 6, first paragraph, second sentence: Change "... entry point
from which on the receiver ..." to "... entry point from which thereafter
the receiver ...".

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