RE: iSCSI: padding on intermediate sequences

[Eddy Quicksall <Eddy_Quicksall@ivivity.com>]

It is the sequences I am speaking of, not the segments. The current wording
of the spec would allow you to send sequences with padding in each sequence
(the segments within the sequence are ok because they can't have padding).
But if a transfer is made up of several sequences then it is more work for
the hardware if intermediate sequences were allowed to have arbitrary pad
bytes.

And there is no good reason (that I am aware of) that intermediate sequences
could not just be pure data.

Now, if there is a reason, then we should come up with a scheme that allows
one party to "just say no". One possibility is that if DataInOrder=yes, then
padding would not be allowed except in the sequence that represents the last
portion of the transfer. 

If that is objectionable, then we should have a new key
(PaddingOnlyInLastSequenceOfTotalTransfer=yes). :-)

Eddy

-----Original Message-----
From: Robert D. Russell [mailto:rdr@io.iol.unh.edu]
Sent: Tuesday, March 26, 2002 2:48 PM
To: Eddy Quicksall
Cc: ips@ece. cmu. edu (E-mail)
Subject: Re: iSCSI: padding on intermediate sequences


Eddy:

I may not be understanding you correctly, but the
words in section 9.7.7 I believe mean that these data
segments should contain an integer number of 4 byte words
of data, not arbitrary "pad" bytes.  If the data segment
length is a multiple of 4 then there will be NO pad bytes.

There seems to be confusion over your use of "pad"
and the standard's use of "pad".  Would you please clarify?

Thanks,
Bob


On Tue, 26 Mar 2002, Eddy Quicksall wrote:

> Section 9.7.7 says:
>
> The Data Segments of Data-in and Data-out PDUs SHOULD be filled to the
> integer number of 4 byte words (real payload) unless the F bit is set
> to 1.
>
> This allows one to pad intermediate sequences of a transfer. But, there
are
> reasons why padding on intermediate sequences within a transfer can make
> life difficult.
>
> Can we forbid padding on all but the last PDU for the transfer? If that is
> objectionable, could we forbid padding on all but the last PDU of a
transfer
> if DataInOrder=yes.
>
> Eddy
>