RE: LUN field in R2T

Bill,

This is left to the implementer. I would argue that a "liberal" initiator 
should store the LUN-TTT fields as they come and not fill them up.

Julo


[email protected] wrote on 01/04/2008 02:36:03 AM:

> Thanks for getting back on this.   I think I still need a little 
clarification.
> 
> In a nutshell all I want to know is this:  Is it legal for an 
> initiator to set the LUN field in the Data-Out PDU based on what it 
> knows the LUN to be, or MUST the initiator copy the contents of the 
> LUN field from the received R2T into the Data Out. 
> 
> Example:  An initiator negotiates for MaxOutstandingR2T==4.  The 
> initiator sends a write command to a target.  The initiator receives 
> an R2T and starts sending multiple Data-Out PDUs.   The initiator 
> receives 3 more R2Ts but cannot start sending Data-Out PDUs 
> immediately due to outbound resource limitations.   The initiator must
> now store off each R2T request so that it can honor them when 
> resources become available ? otherwise the initiator will need to halt
> receive processing on the connection.   The initiator will probably 
> need to store the Target Transfer Tag, Buffer Offset, and Desired Data
> Transfer Length for each R2T.   Does the initiator need to store the 
> LUN from each R2T as well?  Or can it just fill in the LUN in the Data
> Out PDUs based on knowing what LUN the command was sent to in the first 
place? 
> 
> Thanks,
> 
> 
> Bill
> 
> 
> 
> 
> From: Julian Satran [mailto:[email protected]] 
> Sent: Thursday, January 03, 2008 4:12 AM
> To: Sears, Bill
> Cc: [email protected]
> Subject: Re: [Ips] LUN field in R2T
> 
> 
> Your interpretation is more liberal than the text says. The reason for
> requiring a LUN field in the first place was to remove the requirement
> for a  target-wide unique TTT and enable distributed targets that do 
> not require coordination.  The reason LUN was chosen to tag the R2T is
> that it may simplify routing of the data to the appropriate destination. 

> But since it is called LUN some zealous initiator may check (although 
> it is not mandated) the LUN validity versus a list obtained otherwise 
> - so I would not go for a very liberal interpretation. 
> 
> Julo 

> 
> [email protected] 
> 01/02/08 11:57 PM 
> 
> To
> 
> <[email protected]> 
> 
> cc
> 
> 
> 
> Subject
> 
> [Ips] LUN field in R2T
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Just a quick clarification: 
> 
> 10.8.5.  Target Transfer Tag 
> [...]The Target Transfer Tag and LUN are copied in the outgoing data 
> PDUs and are only used by the target. 
> 
> Does this mean that the LUN field in the R2T does not need to contain 
> the actual LUN number specified by the SCSI write?   Since the field 
> is ?only used by the target? I assume this text means that the target 
> may place anything it wants in the LUN field of the R2T and have it 
> echoed back by the initiator. 
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