iSCSI: DLB's Last Call T17 comment

[Black_David@emc.com]

John,

[T.17]  6.4  Format Errors

   The following two explicit violations of PDU layout rules are format 
   errors: 

        a)  illegal contents of the PDU header (except the Opcode) - for 
        ex., out-of-range values for certain fields
        b)  inconsistent contents - for ex., value of one field conflicts 
        with that of another. 
    
   Format errors indicate a major implementation flaw in one of the par-
   ties.

The two "for ex."s aren't good enough.  Details on what is a format error
need
to be spelled out explicitly, given the drastic consequences of committing
one.

> I also disagree with your item T17.  I think those examples are all that
is
> needed, since there are an infinite number of ways for someone to screw
up.
> Much of the document, is spent stating what MUST, SHOULD, SHOULD NOT be
> done, repeating those at this point would not be useful.

A large pile of additional examples is not what's needed - what I asked
for is more precise definitions of "illegal contents" and "inconsistent
contents".  This need only take a few sentences - I think the intent is that
a format error is something that can be determined to be wrong statically
without reference to any session or connection state and is wrong
in a fashion that violates a MUST in the definition of the format
of the appropriate PDU.  For example, setting both the O and U bits
to 1 in a SCSI Response PDU is a format error, but using a bad Initiator
Task Tag (unknown to the Initiator) is not.

The text in the above paragraph starting with "a format error is" should
be most of what's needed to resolve this one, and even includes a couple
of examples that are more specific than the current text.

Thanks,
--David 
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