RE: iSCSI: unsolicited data

["Somesh Gupta" <somesh_gupta@silverbacksystems.com>]

Sandeep,

As discussed earlier, the implementation complexity, especially
in network processor like devices is very different between the
two cases - data in the same order as the commands, and not in
the same order is very different. It is best if as you suggest,
data follows the PDU. In any case, the condition of having the
data follow in the same order as the commands should not be
relaxed at all. Only in the presence of an actual digest error
should this condition be not considered a severe protocol error.

Somesh

> -----Original Message-----
> From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> Sandeep Joshi
> Sent: Friday, November 30, 2001 3:36 PM
> To: ips@ece.cmu.edu
> Subject: Re: iSCSI: unsolicited data
> 
> 
> 
> Julian,
> 
> Perhaps this thread was missed..could you please elaborate on this 
> deadlock issue..when exactly does it occur?  
> Note that I am not asking for out-of-order data!
> 
> There was one more question - regarding the allowance given
> to the initiator to *not* send unsolicited PDUs right after
> the command PDUs, which raises persistent questions.
> 
> See http://www.pdl.cmu.edu/mailinglists/ips/mail/msg07930.html
> for the latest question on this issue.
> 
> IIRC, the reasoning here was that this helps the target in "positioning"
> operations - since it gets a few commands first, and then the data.
> By positioning, do you imply disk/tape seeks or something else ?
> Note that the draft must atleast mention the above rationale if we
> wish initiators to behave as such, and also targets to optimize for it.
> 
> Regards,
> -Sandeep
> 
> "Mallikarjun C." wrote:
> > I however could not really see a deadlock per se - my comment was to
> > understand
> > what it is.    More comments would certainly help.
> >
> > ----- Original Message -----
> > From: "Julian Satran" <Julian_Satran@il.ibm.com>
> > > Mallikarjun,
> > >
> > > The deadlock free requirement here goes a bit deeper than 
> your comment may
> > > suggest.
> > > Unsolicited data needs are very hard to predict and ordering them may
> > > remove the need to do so to a large extent.
>