Re: iSCSI : New PDU opcode usage in rev 5.92

[julian_satran@il.ibm.com]

The former bit of differentian is gone. The main reason we had it was for
analyzers. This is also why I choose the bits as I did.
As for the explanation - I'll check what's already in there.

Julo

Santosh Rao <santoshr@cup.hp.com> on 19/04/2001 19:08:10

Please respond to Santosh Rao <santoshr@cup.hp.com>

To:   ips@ece.cmu.edu
cc:
Subject:  Re: iSCSI : New PDU opcode usage in rev 5.92




That's not a restriction other SCSI transports impose. FCP allows both
the initiator and target bit to be set in PRLI indicating dual mode
behaviour within a single I-T nexus.

However, the point I'm trying to make is that the opcode cannot be
interpreted by itself and needs interpretation in the context of the
"role" the receiver is playing. i.e. Opcode parsing must be in
conjunction with the check of the receiver's role (is it receiving the
command while operating as a target or initiator ?)

Seems like such a description is missing in the draft.

- Santosh



julian_satran@il.ibm.com wrote:
>
> Santosh,
>
> On a given nexus the roles are static aren't they?
>
> Julo
>
> Santosh Rao <santoshr@cup.hp.com> on 19/04/2001 03:47:07
>
> Please respond to Santosh Rao <santoshr@cup.hp.com>
>
> To:   ips@ece.cmu.edu (ips)
> cc:
> Subject:  iSCSI : New PDU opcode usage in rev 5.92
>
> Julian & All,
>
> I've got a quick question on how the new opcode layouts would work for
> dual mode scsi implementations. (i.e. initiators that responded in
> target mode or targets that acted as initiators also).
>
> The new opcode layout is :
>
> ----------------
> X|I| | | | | | |
> ----------------
> 7 6 5 4 3 2 1 0
>
> where bits 5-0 -> opcode
> X -> retry bit
> I -> immediate bit
>
> The same values are used for the command as well as response opcodes and
> bits X & I are intended to both be set to 1 by targets.
>
> i.e. opcode for scsi command = scsi response = 0x01. the distinction b/n
> command and response is based on targets setting X & I bits to 1.
>
> Now, if an initiator [capable of target mode] sent the following
> commands, how would they be interpreted :
>
> 1) 0xc4.
> is this a text command being retried in immediate mode,
> or is it a text response ?
>
> 2) 0xc1
> is this a scsi command being retried in immediate mode,
> or is it a scsi response ?
>
> 3) 0xc2
> is this a scsi task mgmt command being retried in immediate mode,
> or is it a scsi task mgmt response ?
>
> etc.....
>
> - Santosh
>
> --
> #################################
> Santosh Rao
> Software Design Engineer,
> HP, Cupertino.
> email : santoshr@cup.hp.com
> Phone : 408-447-3751
> #################################
 - santoshr.vcf