Re: iSCSI: Reject, CmdSN, and DataSN

[Mark Bakke <mbakke@cisco.com>]

That should work just fine, and will make more of the commands
work the same.  I'll have to think about StatSN; if a Reject
command has a StatSN, it will have to be saved for possible
recovery later, possibly by re-sending the rejected command?
I think it would be better to not include StatSN in Reject
for that reason, although I'm not sure my thoughts are fully
baked on this one.

--
Mark

Julian Satran wrote:
> 
> How about haing all the regular counts back in Reject (including StatSN for
> good measure)?
> 
> Someting like:
> 
>    Byte /    0       |       1       |       2       |       3       |
>       /              |               |               |               |
>      |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
>      +---------------+---------------+---------------+---------------+
>     0|1|1| 0x3f      |1| Reserved (0)                                |
>      +---------------+---------------+---------------+---------------+
>     4| Reserved (0)  | DataSegmentLength                             |
>      +---------------+---------------+---------------+---------------+
>     8/ Reserved (0)                                                  /
>     +/                                                               /
>      +---------------+---------------+---------------+---------------+
>    24| StatSN                                                        |
>      +---------------+---------------+---------------+---------------+
>    28| ExpCmdSN                                                      |
>      +---------------+---------------+---------------+---------------+
>    32| MaxCmdSN                                                      |
>      +---------------+---------------+---------------+---------------+
>    26| Reserved (0)                                                  |
>      +---------------+---------------+---------------+---------------+
>    40| Reason        | Reserved (0)  | First Bad Byte or Rsvd(0)     |
>      +---------------+---------------+---------------+---------------+
>    44| Reserved (0)                                                  |
>      +---------------+---------------+---------------+---------------+
>    48| Digests if any...                                             |
>      +---------------+---------------+---------------+---------------+
>    xx/ Complete Header of Bad PDU                                    /
>     +/                                                               /
>      +---------------+---------------+---------------+---------------+
>    yy
> 
> Julo
> 
> Mark Bakke <mbakke@cisco.com> on 27-07-2001 16:41:15
> 
> Please respond to Mark Bakke <mbakke@cisco.com>
> 
> To:   IPS <ips@ece.cmu.edu>
> cc:
> Subject:  iSCSI: Reject, CmdSN, and DataSN
> 
> When a PDU is rejected, I assume that the CmdSN is still
> updated, as well as the DataSN where applicable.  That is,
> a rejected command still uses up a SN.  It probably wouldn't
> hurt to state this in the reject section.
> 
> Since the Reject response does not contain ExpCmdSN, if the
> last command before the window is closed is rejected, the
> initiator has to rely on prior commands completing to re-open
> the window.  This will usually work, but what if the window
> size is reduced to one outstanding command for some reason?
> Any command that is rejected will close the window for good.
> A sequence of rejected commands equal to the window size will
> do the same.
> 
> Any thoughts?
> 
> --
> Mark A. Bakke
> Cisco Systems
> mbakke@cisco.com
> 763.398.1054

-- 
Mark A. Bakke
Cisco Systems
mbakke@cisco.com
763.398.1054