Re: Error recovery level 2 Question

["Nandakumar Ramamurthy" <nramamur@npd.hcltech.com>]

Hi Kevin,

 

In my understanding, the initiator must wait for

a recovery R2T from the target.

 

This is conveyed by the following sections of the draft :

 

10.17.1
"For iSCSI, Data-Out PDU retransmission is only done if the
target requests retransmission with a recovery R2T."

 

6.2.2 (Allegiance Reassignment)
"In reassigning connection allegiance for a command, the targets
SHOULD continue the command from its current state."

 

"For all types of commands, a reassignment request implies that the
task is still considered in progress by the initiator and
the target must conclude the task appropriately if the target
returns the "Function Complete" response to the reassignment
request. This might possibly involve retransmission of data/R2T/
status PDUs as necessary, but MUST involve the (re)transmission of
the status PDU."

 

From the above it seems to be implied that the target, after returning

the 'Function Complete' response for the "task reassign" request,

might retrasmit 'data' in case of a 'READ' (or) an 'R2T' in case of a 'WRITE'.

 

 

6.1.4.1 (Recovery Within-command)
"To avoid a race with the target, which may already have a recovery
R2T or a termination response on its way, an initiator SHOULD NOT
originate a SNACK for an R2T based on its internal timeouts (if
any). Recovery in this case is better left to the target."

 

 

Thanks,

Nandakumar
Member Technical Staff
HCL Technologies, Chennai, INDIA.
http://www.hcltech.com/san

 

 

----- Original Message -----

From: <kevin_lemay@agilent.com>

To: <Julian_Satran@il.ibm.com>

Cc: <ips@ece.cmu.edu>

Sent: Wednesday, March 05, 2003 4:44 AM

Subject: Error recovery level 2 Question

> Julian,
>  
> Assume that I have a multi-connection 
session to a target when one of the connections fails.
>  
> 
What is the completion of the following diagram (assume 8K PDUs and maxBurst = 
64K):
>  
> 
Initiator                          
Target
> 
----------                        
---------
> Write Cmd (64K no Immediate) --->
> 
                             
<---  R2T Offset 0, len=64K
> Data PDU (8K DataSN 
0)       --->
> Data PDU (8K DataSN 
1)       ---> 
>    --- 
Connection Lost ---
>  
>  
> On 2nd 
connection:
> Logout (for 
recovery)        --->
> 
                             
<---  Logout Response
> Task Mgnt 
(Reassign)         --->
> 
                             
<--- Task Mgnt Response - OK
>  
> What Comes Next?
> 
 
> Is a recovery R2T expected from the target?
> or does the 
Initiator continue to send data PDUs to the target?
>  
> If 
the initiator continues to send, what is the proper place to continue. I may 
have submitted several PDUs to the stack that were never received before the 
connection loss was detected. 
>  
> The read request seems 
fairly straight forward, but the write case is not clear (at least to 
me...)
>  
> Thanks for any help,
>  
> Kevin 
Lemay