Re: iscsi : MaximumBurstSize & FirstBurstSize values.

[Santosh Rao <santoshr@cup.hp.com>]

Robert Snively wrote:

> I am sorry, but I don't think this is a necessary or appropriate

> limitation.  FirstBurstSize is a PDU size, and its characteristics
> are determined by the unsolicited data buffer capability of the
> target.  MaximumBurstSize is a PDU size, and its characteristics
> are determined by the solicited data buffer size and the buffer
> size increments available to the initiator.  These may meet that
> rule, but they may also not meet that rule.  That is why there
> are two values.
>
> It may be important to clarify that FirstBurstSize overrides
> MaximumBurstSize for the first burst.

Bob,

Your solution works fine for me.

The current draft wording is not clear on how the initiator must send
un-solicited data when MaximumBurstSize is < FirstBurstSize, since the
meaning of the "F" bit in the data-out sequence is currently over-loaded to
imply end-of-sequence as well as end-of-unsolicited data. Sequence length
could be construed as less than length of un-solicited data.

Regards,
Santosh



> > -----Original Message-----
> > From: Santosh Rao [mailto:santoshr@cup.hp.com]
> > Sent: Friday, September 21, 2001 11:43 AM
> > To: IPS Reflector
> > Subject: iscsi : MaximumBurstSize & FirstBurstSize values.
> >
> >
> > All,
> >
> > I believe the FirstBurstSize setting has to be <= MaximumBurstSize ? I
> > suggest that this be explicitly called out in the definition of
> > FirstBurstSize.
> >
> > If this rule is not followed, an initiator would need to break the
> > un-solicited data it sends into more than 1 data-out sequence, and in
> > setting the F bit to indicate end-of-sequence, it can confuse
> > the target
> > into thinking its end of un-solicited data.
> >
> >
> > The definitions currently read :
> >
> > "4.1.1 MaximumBurstSize Field (16 bit)
> >
> > This field defines the maximum SCSI data payload in an iSCSI
> > sequence (a
> > sequence of Data-In or Data-Out PDUs ending with a Data-In or Data-Out
> > PDU with the F bit set to one) in units of 512 bytes. The      default
> > value assumed for a new iSCSI session (I_T nexus) is 512 units.
> >
> > 4.1.3 FirstBurstSize Field (16 bit)
> >
> > This field defines the maximum amount of unsolicited data an iSCSI
> > initiator may to send to the target in units of 512 bytes. The default
> > value assumed for a new iSCSI session (I_T nexus) is 128 units. "
> >
> > Regards,
> > Santosh
> >
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