Transport layer retries

Day, Brian Brian.Day at lsil.com
Tue Aug 9 08:12:44 PDT 2005


* From the T10 Reflector (t10 at t10.org), posted by:
* "Day, Brian" <Brian.Day at lsil.com>
*
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Bill...
 
If you follow the tables listed in the state machines (particularly
tables 130, 133, and 134) in section 9.2.6, I believe you will see that
an initiator that doesn't support retries will turn the target's attempt
of the retry into a Command Complete Received confirmation to the app
layer, with the appropriate delivery result error argument.
This would then cause the application layer (section 10.2.2) to send
down an ABORT TASK.
 
However, an initiator should not be NAKing frames just because it does
not support transport retries... it should only for link errors.  
 
Hope this helps...
 
Brian Day
LSI Logic

  _____  

From: Bill Martin [mailto:bill_martin at sierralogic.com] 
Sent: Tuesday, August 09, 2005 8:19 AM
To: t10 at t10.org
Subject: Transport layer retries



SAS 1.1 allows for discovery of whether a target supports transport
layer retries, but in the spirit of SCSI, the standard does not require
that the mode page bit be changeable.  In the event that the mode page
bit is not changeable, and the initiator does not support transport
layer retries, what is the mechanism for stopping continuous retries by
the target until a timeout occurs?  The definition of the retry
mechanism in 9.2.4.4.2 and 9.2.4.5.2 require that if retransmitted frame
is received the initiator shall operate on it properly.  Finally, the
number of times that a frame will be retransmitted is vendor specific,
so if the initiator sends NAK, it may be retried over and over.

 

Thanks for any insight.

 

Bill Martin
Sr. Principal Engineer
Standards and Interoperability
Sierra Logic, Inc.
916 772-3658

916 765-6875 (Cell)
bill_martin at sierralogic.com

 


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<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2>Bill...</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2></FONT></SPAN>&nbsp;</DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2>If you follow the tables listed in the state machines 
(particularly tables 130, 133, and 134) in section 9.2.6, I believe you will see 
that an initiator that doesn't support retries will turn&nbsp;the target's 
attempt of the retry into a Command Complete Received confirmation to the app 
layer, with the appropriate delivery result 
error&nbsp;argument.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2>This would then cause the application layer (section 
10.2.2) to&nbsp;send&nbsp;down an&nbsp;ABORT TASK.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005></SPAN>&nbsp;</DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2>However, an initiator should not be&nbsp;NAKing 
frames&nbsp;just because it does not support transport retries... it should only 
for link&nbsp;errors.&nbsp;&nbsp;</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2></FONT></SPAN>&nbsp;</DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2>Hope this helps...</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2></FONT></SPAN>&nbsp;</DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2>Brian Day</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=301530415-09082005><FONT face=Arial 
color=#800000 size=2>LSI Logic</FONT></SPAN></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> Bill Martin 
[mailto:bill_martin at sierralogic.com] <BR><B>Sent:</B> Tuesday, August 09, 2005 
8:19 AM<BR><B>To:</B> t10 at t10.org<BR><B>Subject:</B> Transport layer 
retries<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">SAS 1.1 allows for discovery of 
whether a target supports transport layer retries, but in the spirit of SCSI, 
the standard does not require that the mode page bit be changeable.&nbsp; In the 
event that the mode page bit is not changeable, and the initiator does not 
support transport layer retries, what is the mechanism for stopping continuous 
retries by the target until a timeout occurs?&nbsp; The definition of the retry 
mechanism in 9.2.4.4.2 and 9.2.4.5.2 require that if retransmitted frame is 
received the initiator shall operate on it properly.&nbsp; Finally, the number 
of times that a frame will be retransmitted is vendor specific, so if the 
initiator sends NAK, it may be retried over and 
over.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Thanks for any 
insight.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P>
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tabIndex=0 w:st="on"><FONT face=Arial size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Bill 
Martin</SPAN></FONT></st1:PersonName><BR><FONT face=Arial size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Sr. Principal Engineer<BR>Standards 
and Interoperability<BR>Sierra Logic, Inc.<BR>916 
772-3658</SPAN></FONT><o:p></o:p></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">916 765-6875 
(Cell)<BR>bill_martin at sierralogic.com</SPAN></FONT><FONT face=Arial size=2><SPAN 
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