Re: iSCSI:Text field in Asynchronous Message

[Stephen Bailey <steph@cs.uchicago.edu>]

> Will there ever be a need for a Target to send an asynchronous Text message
> to the initiators

I can't speak to need, but it is allowed.

My reading of the intent of the spec (I'm not sure it says this as
well as it could, or even at all), is that targets can CERTAINLY
initiate X-* text message exchanges during full-feature mode.  The
semantics of an X-* message is entirely outside the spec, so sending
an X-* message may be a one-way operation (no response required), or a
multiway, handshaking deal, or whatever.

You could perform arbitrary vendor specific (or standardized
elsewhere) communication among targets and initiators using X-*
messages.  However, if your target wants to be a multitransport
creature (||SCSI, FCP & iSCSI), you're better off doing this
communication using some SCSI mechanism.  SCSI doesn't give you a
good, ubiquitous way for target-initiated messaging though, but there
are work-arounds.  What's often used is vendor specific sense on the
next command completion signal that the target wants to say something
to the initiator.

In other words, sure you can, and I suspect that initially many will
use this mechanism, but there are some strong reasons that it might
not take off as THE WAY to do out-of-band communcation.

Steph