Hi Pak,
It was pointed out to me that the Frame Received (ACK/NAK
Not Balanced
applies to the frames received and not on the frames
transmitted.
Therefore, my argument that the connection needs to be
closed in order to report
Device Server detected Data offset Error is not correct.
Sorry for the confusion. I will eat my crow tonight J
Regards,
Larry
From:
owner-t10@t10.org [mailto:owner-t10@t10.org] On
Behalf Of Larry Chen
Sent: Wednesday, July 12, 2006
11:22 AM
To: Seto, Pak-lung; George Penokie
Cc: t10@t10.org
Subject: RE: SAS error recovery
use case - Device Server detected Data Off set Error
Hi Pak,
ST_IFR imposes the interlocked rules
when it receives Frames.
Therefore, if the target port wants
to insure that the Check condition
is not discarded by the ST_IF then
it must force ACK/NACK balance
by closing the connection.
Taken from SAS-1-1 rev 10 page 370
9.2.6.2.2.3
Processing Frame Received confirmations
If this state machine receives a
Frame Received (ACK/NAK Balanced) confirmation or Frame Received (ACK/
NAK Not Balanced) confirmation, then
this state machine shall compare the frame type of the frame received
with the received confirmation (see
table 118 in 9.2.1). If the confirmation was Frame Received (ACK/NAK
Balanced) and the frame type is not
XFER_RDY, RESPONSE, or DATA, then this state machine shall discard
the frame. If the confirmation was
Frame Received (ACK/NAK Not Balanced) and the frame type is not DATA,
then this state machine shall
discard the frame.
From: Seto, Pak-lung
[mailto:pak-lung.seto@intel.com]
Sent: Wednesday, July 12, 2006
5:27 AM
To: George Penokie; Larry Chen
Cc: t10@t10.org
Subject: RE: SAS error recovery
use case - Device Server detected Data Offset Error
From:
owner-t10@t10.org [mailto:owner-t10@t10.org] On
Behalf Of George Penokie
Sent: Thursday, July 06, 2006 3:44
PM
To: Larry Chen
Cc: t10@t10.org
Subject: Re: SAS error recovery
use case - Device Server detected Data Offset Error
Larry,
The
answers to your questions are as follows:
1 -
Under normal operations an SSP_RESPONSE can be sent in the same connection, but
it is not possible to do that if there is a error detected at the link layer.
[Seto] But Data Offset Error is not a link
layer error, it is a Transport Layer error, right?
That's because any of the errors you
are asking about cause the connection to be closed by the link layer. So the
answer to your specific error case in no a new connection is required to
transmit the SSP_RESPONSE.
[Seto] Don’t see why it needs a new
connection to transmit SSP_RESPONSE.
2- This cannot happen as the connection is automatically closed when an
ACK/NAK timeout occurs.
[Seto] I thought Larry’s is
questioning about – SSP_RESPONSE is received before ACK/NAK timeout?
3- Effectively yes. All the SSP state machines stop running when either the
Request Close message or the Request Break message is sent by the SSP_D state
and do not start up again until an Enable Disable SSP message is received.
4- The
only two timers that overlap are the ACK/NAK Timeout timer and the Credit
Timeout timer. Both of those timers can cause an action by the SSP_TF2Tx_Wait
state. The description on the priority is in section 7.16.8.6.3.3 Transition
SSP_TF2:Tx_Wait to SSP_TF4:Transmit_DONE. Basically the ACK/NAK Timeout timer
has priority over the Credit Timeout timer.
The
DONE timeout timer is only relevant after a Transmitted DONE message is
received by the SSP_D state at which time no other link layer timer is
relevant.
The
other link layer timers are:
The
Open Timeout timer - That timer is only used when the SL_CC state machine is in
the SL_CC!:ArbSel state. It is initialized on entry and control is completely
defined within that state.
The
Close Timeout timer - That timer is only used when the SL_CC state machine is
in the SL_CC4:DisconnectWait state. It is initialized on entry and control is
completely defined within that state.
The
Break Timeout timer - That timer is only used when the SL_CC state machine is
in the SL_CC5:BreakWait state. It is initialized on entry and control is
completely defined within that state.
Bye
for now,
George Penokie
E-Mail: gop@us.ibm.com
Internal: 553-5208
External: 507-253-5208
|
Larry Chen
<Larry_Chen@pmc-sierra.com> 06/29/2006
07:07 PM |
|
Hi,
I have
an SAS error recovery use case which can not
Solve
by myself after reading the SAS-1.1 specification Rev 9e.
The
use case scenario starts when the Device Server detects
A Data
Offset Error (assume that the first of two data
Frames
is dropped/lost) during a Write command.
As
stated in the spec, the Device Server sets the appropriate
SCSI error
message in the SSP_RESPONSE frame and sends
It to
the initiator.
Ex)
Initiator
Target
---------------SSP_Command(WRITE)------------à
ß-----------------------------ACK-------------------------
ß----------------------------SSP_XFR_RDY----------
---------------------------------ACK-----------------------à
--------------SSP_DATA-1-------------à
DROPPED/LOST
--------------SSP-DATA-2------------------------------à
Data Offset Error is detected
ß------------------------------ACK-2-----------------------
ß-----------SSP_RESPONSE(DATA_OFFSET_ERROR)
QUESTION-1:
Can SSP_RESPONSE be sent in the same connection
Or
does it need to open a new connection?
QUESTION-2:
If SSP_RESPONSE is received when ACK-TOV is still
Running,
is the ACK_TOV timer supposed to be cancelled? If so, can someone
Refer
me to the place in the SAS spec where this is mentioned.
QUESTION-3:
Does closing a connection force cancelling of all
Active
timers, such as, ACK_TOV timer?
QUESTION-4:
does SAS spec mention about how ACK_TOV,
DONE_TOV,
AND BREAK_TOV timers interact e.g. priority, preemption?