RE: iSCSI: Use of the A bit

[Eddy Quicksall <Eddy_Quicksall@ivivity.com>]

By status ack, if you mean a SCSI Response with ExpStatSN, then that does not acknowledge the Data-In unless the Data-In was followed by status.

 

Julian, all we are asking is that you don't create a spec that has a pitfall. If one is worried about performance then he should work that out by not asking for the Ack in the first place. Don't mandate it in the spec, just say it in a note.

 

Eddy

-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Friday, March 15, 2002 2:51 PM
To: Paul Koning
Cc: Eddy_Quicksall@ivivity.com; ips@ece.cmu.edu; owner-ips@ece.cmu.edu; rod.harrison@windriver.com
Subject: RE: iSCSI: Use of the A bit

That could be so but it would be overkill. Status ACK can implicitly acknowledge the last transfer.
And Yes the fact that the last transfer is not mentioned is an oversight that I will correct.
This does not mean that you HAVE TO raise the A flag or that you are ENCOURAGED to do so :-)

Julo

Paul Koning <ni1d@arrl.net> Sent by: owner-ips@ece.cmu.edu 15-03-02 16:09 Please respond to Paul Koning

To:        Eddy_Quicksall@ivivity.com         cc:        rod.harrison@windriver.com, ips@ece.cmu.edu         Subject:        RE: iSCSI: Use of the A bit

>>>>> "Eddy" == Eddy Quicksall <Eddy_Quicksall@ivivity.com> writes:

Eddy> I think we may need better explanation about why some folks
Eddy> don't want to do the "positive ack".

>> We got to this position, since so many folks did not want to
>> support the positive ack.

Something doesn't compute here.

I don't believe the discussion has anything to do with whether you
support positive ACK or not.  If you're doing error recovery level 1
or above, then you are required to support it, because the other end
is allowed to say A=1 and you're required to answer that.

If you don't want to support positive ACK, the solution is to support
only error recovery level 0.

The issue under discussion is whether the rule "you are allowed to set
A=1 only once per MaxBurstSize" is correct.  At this point it's clear
to me that it is not, because you need to be able to set A=1 at the
end of the transfer.  The current rule forbids that unless the total
transfer size is >= MaxBurstSize.

Kevin's proposal is a simple fix to this problem.

                 paul