iSCSI: Feeling a little peckish?

[Ken Sandars <ksandars@eurologic.com>]

Hi Julo,

I'm looking to confirm the SNACK requirements from a target's perspective for 
each negotiated ErrorRecoveryLevel. Can you (or any other error handling 
expert - Mallikarjun?) confirm I captured the gist please?



TARGET's perspective:

SNACK type            ERL=0                        ERL>0
------------------------------------------------------------------
status                      optional                      mandatory*
                              (silently discard)

data/r2t                    optional                      mandatory
                              (reject,
                               reason=3)

data ACK                 optional                      optional
                              (target never 
                              sets the A bit)


* Para 9.16.2 states that 'if the target supports recovery within connection, 
it MAY discard the SNACK after which it MUST issue an Asynchronous Message 
PDU with an iSCSI event that indicates "Request Logout"'.

Question: Is support for "recovery within connection" mandatory if the ERL 
has been negotiated to be > 0?


To complete the picture,

INITIATOR's perspective:

SNACK type            ERL=0                        ERL>0
------------------------------------------------------------------
status                      optional                      mandatory**
                                                               
data/r2t                   optional                       mandatory**

data ACK                optional                       mandatory
                            (can ignore the A bit)


** As the SNACK is sent by the initiator, it is up to it to decide whether to 
do this, or to escalate recovery. Is this more of a SHOULD support than a 
MUST, or am I missing something?


Cheers,
Ken


Ken Sandars
Eurologic Systems, Ltd
ksandars@eurologic.com