Re: iscsi : MaximumBurstSize & FirstBurstSize values.

["Sanjeev Bhagat \(TRIPACE/Zoetermeer\)" <iscsi_t10@sanjeevbhagat.com>]

----- Original Message -----
From: "Santosh Rao" <santoshr@cup.hp.com>
To: "IPS Reflector" <ips@ece.cmu.edu>
Sent: Friday, September 21, 2001 11:20 PM
Subject: Re: iscsi : MaximumBurstSize & FirstBurstSize values.


> 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,

Although I agree with Bob here but isnt it worth thinking, why should the
firstburstsize be greater than MaximumBurstSize. I think in all practical
implemetation firstburstsize will be lesser than MaximumBurstSize.

Considering bob's explanation, It will not be a good idea to put any
restrictions with respect to size but  just to avoid some confusion it might
be better to rename FirstBurstSize as UnsolicitedBurstSize and
MaximumBurstSize as MaximumSolicitedBurstSize.

>
> 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
> > >
>