Re: iscsi : Fragmentation & Reassembly issues in iSCSI.

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

julian_satran@il.ibm.com wrote:

> <js> I will introduce in 04 a statement saying that that PingMaxRelayLength
> will be limited by the lowest of the two </js>

Julian,

The fragmentation issue as explained in the above example is also applicable
for the Login and Text Commands. (TotalText > DataPDULength).

In the case of these commands, a "F" bit is required in bit 7 of byte 1 of the
command & response PDUs to indicate the last command or response PDU due to
the fragmentation issues that arise from TotalText & DataPDULength.


> Solution :
> =======
> Specify explicitly in Appendix C that DataPDULength is only applicable
> for SCSI Command PDU and SCSI Data PDU. The current definition is open
> to being mis-interpreted as a form of iSCSI MTU, something that can
> result in the iSCSI layer having to deal with fragmentation and
> re-assembly issues for non-SCSI PDUs.
>
> <js> What would be those? Text commands? Login? Nops? Having a single limit
> seemms simpler </js>

On the lines of your above solution, (based on a single limit), removal of
PingMaxReplyLength should be considered and implicitly use DataPDULength as
the PingMaxReplyLength. This ensures only 1 limit for NOP-OUT/NOP-IN.

Regards,
Santosh
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