Re: iSCSI: using the C bit

[Carlos Rimola <crimola@silverbacksystems.com>]

At 06:24 PM 1/16/2003 -0500, Eddy Quicksall wrote:
> I want to be sure I understand the
> use of the C bit in a login. It seems to
> me that the initiator could split a key into two parts: 1st part at the
> end
> of request A and 2nd part at the beginning of request A+1.
>  
> e.g., the end of request A (with C bit set) could be
> "Immediate" and the
> beginning of request A+1 could be "Data=yes" (the full
> key=value pair being
> "ImmediateData=yes").
>  
> If this is done, the target will not process the partial key and may
> send
> his own key saying "ImmediateData=no". But, the initiator has
> already
> constructed the negotiation and request A+1 would violate the
> protocol
> because ImmediateData has already been negotiated.
>  
> Comments?
>  
> Eddy

Eddy,

This scenario - the target sending his own key while the Initiator is
still sending partial chunks (by setting C Bit = 1) would be a violation
of the rule specified in 5.2 (Text Mode Negotiation) which applies during
Login as well as Text Req/Resp:

A target receiving a Text or Login Request
with the C bit set to 1
MUST answer with a Text or Login Response with no data segment
(DataSegmentLength 0). An initiator receiving a Text or Login
Response with the C bit set to 1 MUST answer with a Text or Login
Request with no data segment (DataSegmentLength 0).


The target can begin sending its own keys only when a PDU with the
C Bit set to 0 arrives.  At this point, all keys will be complete
and the above condition is avoided.

Regards,

Carlos Rimola
Silverback Systems