RE: iSCSI 05.txt is out

["Venkat Rangan" <venkat@rhapsodynetworks.com>]

Julian,

Here are a few technical and editorial comments on the latest draft.

Technical:

Page 12:

- CmdSN - the current Command Sequence Number advanced by 1 on each command
shipped

Add: skipping zero, which is reserved for immediate delivery.

Page 12:
Remove the sentence:
"A large difference between StatSN and ExpStatSN may indicate a failed
connection."

This may have made sense when StatSN and ExpStatSN are session-wide. Now
that it is per-connection, this may not be valid. As was pointed out in the
"Holes in StatSN" thread, ExpStatSN may be "stuck" at a low value when a
single PDU encountered a Digest Error, followed by several well-formed PDUs.

Page 24 - Section 2.1
Add: The length of the PDU SHALL include any padding bytes added.

This raises a question as to whether it may be useful to include a two-bit
"Fill Bytes" field in the header (BHS and AHS) which indicates the number of
bytes that were added. Without this, it may be harder for the receiver to
know how many bytes are part of the data. Fibre Channel has the Fill Byte
specifier in its F_CTL part of the header.

Page 25:
This may be covered in another thread.

What does the first Next-Qualifier (at byte 0) describe? Is it the BHS or
the header following the BHS? If a PDU has a single BHS and a single AHS, is
the sequence WN-BHS-AHS or is it WN-BHS-WN-AHS?

Page 25 and 26:
The text next to the bit description and the headers in the text for
sections 2.2.2.1 to 2.2.2.3 appear to be inconsistent.  An example is
"read-data transfer" vs. "Read Data" "Long Data" vs. "Long Data Transfer"

Also, 2.2.2.3 appears to have text about Long Data Header that probably
belongs in section 2.2.2.2 (or I am confused about how WN is supposed to
work.)

Page 43
Section 2.7
The PDU diagrams should not show "Digests if any..." etc. It should be
covered by NQ and corresponding AHS.

Page 44
Section 2.7.2
The requirement of having to specify a valid LUN as part of WRITE Data (and
NOP-Out) may pose unnecessary overhead for Target processing. The fact that
Targets are now REQUIRED to reject errant initiators who may place a LUN
inconsistent with the one sent in the CommandPdu means that targets should
save the LUN against each context entry for the task. This was discussed
earlier, and I think we said that unless the folks who originally wanted it
spoke up, we will remove it. Note that Fibre Channel does not have this
feature, and its original purpose can be accomplished by using Target
Transfer Tag.

If we still want it, targets should be given the option of negotiating this
so that it can operate in a mode where a LUN specified as part of WRITE data
will be ignored (as opposed to rejected).

Section 2.17
The following text:
"Within a connection, outstanding R2Ts MUST be fulfilled by the initiator in
the order in which they were received."

implies that R2Ts for the same WRITE command may be sent by the target on
multiple connections? Since this is not possible, all R2Ts for a command are
always on a single connection, so I am not sure how the above sentence
should be interpreted.

Page 75:
Add: "i.e., from Most Preferred to Least Preferred" to "reverse order of
preference."

------------
Editorial - typos and such

1. Page 11:

Not covered are he means

Change "he" to "the"

2. Page 20:

Change "later" to "latter" in "the later can be used in subsequent
commands."

3. Page 23:

Change "isa"  to "is a"

Page 42:
Section 2.6.1
Change to: Initiator Task Tag of the task that was not found; used in
conjuction with Response value 1. It MUST be set to zero in other cases.

Page 51:
Change "CID does not change and this command is performs first" to

"CID does not change and this command first performs"

Page 55:
There is nothing that indicates the status codes in the table are sent as
part of Status-Detail.

Page 66:
Change "iSSCSI Data-out PDU" to "iSCSI Data (WRITE) PDU"

The Data-out PDU is a new concept not introduced anywhere.

Page 75:
The term "Security Context Complete" is referred to prior to its definition.

Page 81:
Change "later" to "latter"

------------

Venkat Rangan
Rhapsody Networks Inc.
http://www.rhapsodynetworks.com