iSCSI error recovery

[Black_David@emc.com]

There's been a lot of discussion on the list about this
topic, including the proper use of CmdSN and StatSN
to respond to errors including those detected by CRC.
I hesitate to call consensus on any of this discussion
because it's based on a version of the draft (-03) that
is some combination of incomplete, incorrect, and/or
difficult to comprehend in this area.  Based on this
and the length/detail of the discussion, I suspect
that many people on the list are not completely aware
of the issues here, and calling consensus when a large
segment of the WG may not understand the issues is
unlikely to be productive.

The next version of the draft (-04) SHOULD contain a
much better section on error recovery with explanations
and examples that make it significantly easier to
understand.  Consensus calls on error recovery will not
be made before it appears.

Meanwhile, a few comments on ongoing issues:
- If a CRC error occurs, trying to use any data covered
	by that CRC is generally not a good idea in the
	absence of other measures (e.g., an error-correcting
	code covering the field(s) of interest).
- Given some of the CRC discussion, I think the conclusion
	in Orlando to have separate header and data CRCs is
	NOT the rough consensus of the WG.  We need to go
	back to a requirements discussion on this rather than
	debating exactly where to put the CRCs.  Would those
	envisioning middleboxes/gateways/etc. that would
	benefit from this sort of CRC separation please post
	short use cases/descriptions indicating the basic
	functionality of the box and which fields it needs
	to change (let's do this with reference to the header
	layout in -03 rather than subsequent changes)?  As
	part of the use case/description, please explain
	how/why Fibre Channel's single CRC covering both
	the frame header and data causes problems/difficulties.
- Mandating the use of IPsec or TLS solely to handle
	CRC-level integrity issues is overkill.

Thanks,
--David

---------------------------------------------------
David L. Black, Senior Technologist
EMC Corporation, 42 South St., Hopkinton, MA  01748
+1 (508) 435-1000 x75140     FAX: +1 (508) 497-8500
black_david@emc.com       Mobile: +1 (978) 394-7754
---------------------------------------------------