Re: MaxRecvPDULength question

["Robert D. Russell" <rdr@io.iol.unh.edu>]

Julian:

It has been stated several times that at this late stage we
should not be requesting changes that are just preferences.

Nevertheless, due to apparent misunderstandings of its meaning,
the key named MaxRecvPDULength in draft 12 is apparently going
to have its name changed in draft 13.

Fine.  No problem.

However, to remove all possibility of future misunderstandings,
why don't we give it a name that says precisely what it is:

MaxRecvDataSegmentLength

That way, the first sentence in the third paragraph of section
9.7.1 would begin:

"DataSegmentLength MUST not exceed MaxRecvDataSegmentLength
 for the direction it is sent ..."

which seems to me to be the classic definition of a maximum.

The issue of changing the name from MaxRecvPDULength started with an
e-mail sent by Luben Tuikov on 21 May (who, by the way, did NOT want
to change the name, just its meaning), and was followed by a short
flurry of e-mails under the thread "MaxRecvPDULength question".

Some of the names suggested on that thread were:
  MaxRecvDataLength        (21 May by Paul Konig)
  MaxRecvDataSegmentSize   (21 May by Pat Thaler)
  MaxRecvDataSegSize       (21 May by Pat Thaler)
  MaxRecvPDUDataSize       (22 May by Pat Thaler)

and what got into the draft was this last suggestion by Pat.

I don't believe there was a consensus for this choice (probably, as
was stated by Pat several times, because most people don't really see
the need for a renaming and didn't bother to participate in the thread).
Therefore, I would ask you to reconsider the new name and ask for
consensus on the new choice.

I believe the name MaxRecvDataSegmentLength is so closely linked to the
name DataSegmentLength that its meaning should be clear to even a
first-time reader, especially given the statement in section 9.7.1
quoted above.

Furthermore, there clearly is the concept of DataSegmentLength elsewhere
in the standard -- every PDU has a DataSegmentLength field.
I could find no concept of PDUDataSize (or even "data size") elsewhere in
the current draft.


Whether or not this renaming happens (again), I believe there should be
the following rewordings to be more precise in order to avoid any
ambiguities and/or future misinterpretations.

The first sentence in section 9.10.5 should be changed to read:

 "The DataSegmentLength in a Text Request MUST NOT exceed the
 iSCSI target's MaxRecvDataSegmentLength (a per connection and per
 direction negotiated parameter)."

and the first sentence in section 9.11.6 should be changed to read:

 "The DataSegmentLength in a Text Request MUST NOT exceed the
 iSCSI initiator's MaxRecvDataSegmentLength (a per connection and per
 direction negotiated parameter)."

Finally, two sentences in section 11.13 should be changed to read:

 "The initiator or target declares the maximum DataSegmentLength in
 bytes it can receive in an iSCSI PDU."

and

 "The transmitter (initiator or target) is required to send PDUs with a
 DataSegmentLength not exceeding MaxRecvDataSegmentLength of the receiver."


Thank you for your consideration,


Bob Russell
InterOperability Lab
University of New Hampshire
rdr@iol.unh.edu
603-862-3774