Re: iSCSI: draft 7: remove S bit and Status field from the Data-i

[Sandeep Joshi <sandeepj@research.bell-labs.com>]

Julian,

I wonder if Dave's last paragraph in this email has been considered.
Here it is again..

> This does help some. It eliminates the situation where a target can receive
> an essentially unlimited number of immediate data commands prior to receiving
> *any* data PDUs.

in reference to Section 1.2.5
> Unsolicited data MUST be sent on 
> every connection in the same order in which commands were sent.

The draft currently allows 
   c-1,c-2,c-3, (SEP-1-1),(SEP-1-2),(SEP-2-1,SEP-2-2),..
where c-N = command {N}
and   SEP-N-M = unsolicited (non-immediate) PDU number {M} for command
{N}

It would be simplify target login (ITT lookup) if we only permitted
this sequence. 
   c-1, SEP-1-1, SEP-1-2, c-2, SEP-2-1, SEP-2-2,..

-Sandeep


Dave Sheehy wrote:
> 
> David,
> 
> > I think you've taken a wrong turn.
> 
> I think John hit the nail on the head.
> 
> > > Second, thoughts of removing the immediate data seem not to be
> > > simplification, since all the information to tie the data to the command
> > is
> > > right there with the command.  That has got to be easier than matching up
> > > separate PDUs of data with the appropriate commands.
> >
> > Actually, that was the point, since the logic for "matching up separate
> > PDUs of data with the appropriate commands" has to exist for inbound
> > Data PDUs already.
> 
> Except that there is a target context present in the solicited case to route
> the data. That doesn't exist in the unsolicited case.
> 
> > The slide I presented in London was about replacing
> > immediate data with an unsolicited data PDU immediately following the
> > command, thus removing the immediate data case in favor of reusing the
> > logic for dealing with separate Data PDUs.  Remember that this was presented
> > as a simplification possibility.
> 
> This does help some. It eliminates the situation where a target can receive
> an essentially unlimited number of immediate data commands prior to receiving
> *any* data PDUs.
> 
> But, do you mean to say that *one* unsolicited data PDU would follow the
> command? Wouldn't that be unnecessarily restrictive if the PDU size is small?
> Simply guaranteeing that the data PDUs will immediately follow the command
> seems like an adequate improvement.
> 
> Dave Sheehy