FCP-3: Obsolete FCP_DL and FCP_BIDIRECTIONAL_DL

phil.colline at dothill.com phil.colline at dothill.com
Thu Sep 30 13:30:54 PDT 2004


* From the T10 Reflector (t10 at t10.org), posted by:
* phil.colline at dothill.com
*
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I believe it would be a big mistake to obsolete FCP_DL.  The only other
way to determine the transfer size is to crack the payload (CDB) which
would put undue burden on hardware or software layers that currently
rely exclusively on FCP_DL.  While it is a true statement that the
FCP_DL is redundant with the CDB transfer length, forcing the many
existing implementations relying on FCP_DL to utilize the CDB instead
over an orthogonal issue is not the proper solution.  It also seems like
an invitation to renew a whole new set of interoperability problems.
 
Regards,
 
Phil
 
 
On Tue, 28 Sep 2004, David Peterson (Eng) wrote:
 
> * From the T10 Reflector ( t10 at t10.org <mailto:t10 at t10.org> ), posted
by:
> * "David Peterson \(Eng\)" < david_peterson at cnt.com
<mailto:david_peterson at cnt.com> >
> *
> Howdy All,
> 
> During the discussion of T10/03-393 at the recent CAP meeting the
notion
> of obsoleting the FCP_DL and FCP_BIDIRECTIONAL_READ_DL fields in FCP-3
> was mentioned.
> 
> A bit of history that got us to this point:
> 
> The FCP-3 working has been looking at an issue where the FCP_DL value
is
> not equal to the CDB transfer length. The goal is/was to provide a
> method to report this condition to the upper layer(s). The need for
this
> method drops significantly if the FCP_DL fields are obsolete. The
method
> may still have merit since there are other conditions such as the
WRDATA
> bit is set to one in a read type command and vice-versa. But no one
has
> really identified this is a problem case to date.
> 
> Additional reasons to obsolete such as "its redundent with the CDB
> transfer length" and "FCP is the only SCSI transport protocol that
> specifies a data length" have been mentioned.
> 
> Please indicate any preferences for or against obsoleting the FCP_DL
and
> FCP_BIDIRECTIONAL_DL fields along with your reasoning.
> 
> Thanks...Dave
> *
> * For T10 Reflector information, send a message with
> * 'info t10' (no quotes) in the message body to  majordomo at t10.org
<mailto:majordomo at t10.org> 
> 
 

 


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<div class=3DSection1><pre><font size=3D2 face=3D"Courier New"><span
style=3D'font-size:10.0pt'>I believe it would be a big mistake to =
obsolete FCP_DL.&nbsp; The only other way to determine the transfer =
size is to crack the payload (CDB) which would put undue burden on =
hardware or software layers that currently rely exclusively on =
FCP_DL.&nbsp; While it is a true statement that the FCP_DL is redundant =
with the CDB transfer length, forcing the many existing implementations =
relying on FCP_DL to utilize the CDB instead over an orthogonal issue =
is not the proper solution.&nbsp; It also seems like an invitation to =
renew a whole new set of interoperability =
problems.<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'><o:p>&nbsp;</o:p></span></font></pre><pre><fo=
nt
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'>Regards,<o:p></o:p></span></font></pre><pre><=
font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'><o:p>&nbsp;</o:p></span></font></pre><pre><fo=
nt
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'>Phil<o:p></o:p></span></font></pre><pre><font=

size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'><o:p>&nbsp;</o:p></span></font></pre><pre><fo=
nt
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'><o:p>&nbsp;</o:p></span></font></pre><pre><fo=
nt
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>On Tue, =
28 Sep 2004, David Peterson (Eng) =
wrote:<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'><o:p>&nbsp;</o:p></span></font></pre><pre><fo=
nt
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> * =
>From the T10 Reflector (<a
href=3D"mailto:t10 at t10.org">t10 at t10.org), posted =
by:<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> * =
"David Peterson \(Eng\)" <<a
href=3D"mailto:david_peterson at cnt.com">david_peterson at cnt.com><o:=
p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
*<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
Howdy All,<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'>><o:p>&nbsp;</o:p></span></font></pre><pre=
><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
During the discussion of T10/03-393 at the recent CAP meeting the =
notion<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> of =
obsoleting the FCP_DL and FCP_BIDIRECTIONAL_READ_DL fields in =
FCP-3<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> was =
mentioned.<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'>><o:p>&nbsp;</o:p></span></font></pre><pre=
><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> A =
bit of history that got us to this =
point:<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'>><o:p>&nbsp;</o:p></span></font></pre><pre=
><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> The =
FCP-3 working has been looking at an issue where the FCP_DL value =
is<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> not =
equal to the CDB transfer length. The goal is/was to provide =
a<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
method to report this condition to the upper layer(s). The need for =
this<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
method drops significantly if the FCP_DL fields are obsolete. The =
method<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> may =
still have merit since there are other conditions such as the =
WRDATA<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> bit =
is set to one in a read type command and vice-versa. But no one =
has<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
really identified this is a problem case to =
date.<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'>><o:p>&nbsp;</o:p></span></font></pre><pre=
><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
Additional reasons to obsolete such as "its redundent with the =
CDB<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
transfer length" and "FCP is the only SCSI transport protocol =
that<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
specifies a data length" have been =
mentioned.<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'>><o:p>&nbsp;</o:p></span></font></pre><pre=
><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
Please indicate any preferences for or against obsoleting the FCP_DL =
and<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
FCP_BIDIRECTIONAL_DL fields along with your =
reasoning.<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'>><o:p>&nbsp;</o:p></span></font></pre><pre=
><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
Thanks...Dave<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> =
*<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> * =
For T10 Reflector information, send a message =
with<o:p></o:p></span></font></pre><pre><font
size=3D2 face=3D"Courier New"><span style=3D'font-size:10.0pt'>> * =
'info t10' (no quotes) in the message body to <a
href=3D"mailto:majordomo at t10.org">majordomo at t10.org<o:p></o:p></span=
></font></pre><pre><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'>><o:p>&nbsp;</o:p></span></font></pre><pre=
><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt'><o:p>&nbsp;</o:p></span></font></pre>

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