Re: Send Reject PDU when orignal to-be-rejected PDU is notavailable

Jason,
 
The CmdSN window allows the target to control the resources consumed
by commands.  I don't understand the need to save "all PDU header
comes from the Initiator until corresponding statSN is explicitly
ACKed".  What purpose is that accomplishing (e.g., why save all
the iSCSI Data-Out PDU headers for a SCSI WRITE)?
 
In any case, the original PDU header is required for a Reject in order
for the initiator to figure out what was rejected.  If the initiator
cannot figure that out, it is going to have a very difficult time
recovering from the Reject.
 
Thanks,
--David
----------------------------------------------------
David L. Black, Distinguished Engineer
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953             FAX: +1 (508) 293-7786
[email protected]        Mobile: +1 (978) 394-7754
----------------------------------------------------

________________________________

	From: [email protected] [mailto:[email protected]] On Behalf Of HUJason
	Sent: Tuesday, April 15, 2008 11:46 PM
	To: Black, David; [email protected]
	Subject: Re: [Ips] Send Reject PDU when orignal to-be-rejected PDU is notavailable
	 
	
	Hi David,
	
	Thank you for the suggestion. A little more to consider is that it seems that whatever mechanisms we use, as a target, we must reserve all PDU header comes from Initiator until the coressponding statSN is explicitly acked. For a resource-limted iscsi target engine(all SCSI data is on host, so it is not in this question), It can be considered as a big memory consumer and becomes a bottlenack. 
	
	
	Best Regards,
	Jason
	

________________________________

		From: [email protected]
		Subject: RE: [Ips] Send Reject PDU when orignal to-be-rejected PDU is notavailable
		Date: Tue, 15 Apr 2008 23:04:15 -0400
		To: [email protected]; [email protected]
		
		
		The original PDU header has to be sent back so that the initiator
		knows what was rejected.  iSCSI has a number of mechanisms that
		can be used by the target to control resource consumption and
		those should be used to ensure that adequate resources are
		available to deal with the PDU that is to be rejected.
		 
		Thanks,
		--David
		----------------------------------------------------
		David L. Black, Distinguished Engineer
		EMC Corporation, 176 South St., Hopkinton, MA  01748
		+1 (508) 293-7953             FAX: +1 (508) 293-7786
		[email protected]        Mobile: +1 (978) 394-7754
		----------------------------------------------------
		

________________________________

			From: [email protected] [mailto:[email protected]] On Behalf Of HUJason
			Sent: Tuesday, April 15, 2008 9:59 PM
			To: [email protected]
			Subject: [Ips] Send Reject PDU when orignal to-be-rejected PDU is notavailable
			
			
			Dears,
			

				I am curently implement iscsi target on a resource-limted device. In my implementation, orignal to-be-rejected PDU is not available when it realised that a Reject should be sent to initiator.
				 
				But as RFC3720 said, Target must send back the orignal PDU as the Reject's payload. 
				 
				So my question is: Why we need to send back the orignal PDU ? Can we simply eliminate it?
				 
				Thanks!
				

			Best Regards,

			Jason 


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