Re: iSCSI: Canonical Targets

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

Mark,

This is mostly fine with me.  However, I KNOW implementors are going
to gripe about having to know the target name before performing an
operational login.  In general, the spec seems a bit capricious about
when implementors just have to suck it up and do the hard thing,
versus when we try to make it easy for them.  Realistically, it's not
a big deal to learn the name (just an extra login), but most end
points are going to have a single target, and from a configuration
standpoint endpoint (and, hence the target) is going to be specified
by transport coordinates (address, port).  This extra login for
discovery is simply an irritant.

Also,  I think this part still needs a little more specification work:

> 6. We can further specify the order in which the SendTargets response
>    fields are returned, to simplify things further, e.g. each target
>    in the SendTargets response MUST return these fields in this order:
> 
>    - A TargetName= field
>    - A TargetAlias= field (value left blank if there's no alias)
>    - One or more TargetAddress= fields
>    - Any vendor-specific fields (ignored by standard initiators)

I can only guess that you are implying that target descriptions
following this rule may be tiled arbitrarily into Text PDUs returned
from the target?  If so, we should specify that.

> 1. Should a non-canonical target respond to a SendTargets command?

I'd say no.  Given the nature of the interaction, why bother?  Now, I
know the iSCSI philosophy seems to be `if it's not complete gibberish,
why NOT bother?' but that results in complicated implementation.
Specifically, each end (target and initiator) should be able to audit
the other for correctness when possible.  Hard rules like `thou shalt
not issue a SendTargets in an operational session' make the auditing a
zillion times easier.

To this end, I would go a step further and allow only a single
outstanding SendTargets exchange in a target discovery session.

Steph