Subject: iSCSI: new state diagrams for rev09

From: "Mallikarjun C." <[email-masked]>
Date: Fri, 02 Nov 2001 10:32:30 -0800

All:

Consequent to the feedback I received both online and
offline, iSCSI state diagrams are considerably revamped.
Thanks to all those who provided the feedback.  The new
state diagrams are posted at:

	http://storage-arch.hp.com/iscsi_states_rev09.pdf

The ASCII forms of the above are currently part of rev 08-90
draft that Julian posted on his web.

The major changes are -

- The initiator and target state machines are split for 
  both standard connection diagram and session state 
  diagram.  It is hoped that this separation makes it
  easier to follow.

- Several (informative, but) non-essential states were
  eliminated, since they were waiting for internal events 
  (like acquiring resources) that are likely non-existent 
  in good implementations.  That leaves us with a 7-state
  machine for both initiator and target.

- The reduction of states has a salutary effect on the ASCII
  representation.  I was able to translate all the diagrams
  into ASCII!

- The state descriptions are more descriptive now, specifically
  calling out the event(s) that the state machine is waiting 
  for in that state.

- The transition descriptions are also more descriptive,
  listing the set of events that causes the given transition
  for each of the roles.

- The "connection recovery state diagram" has been renamed 
  as "connection cleanup state diagram" since the word "recovery"
  was inadvertently overloaded.  Connection recovery (the 
  act of reassigning the task allegiance to a different connection)
  happens outside the scope of this state machine depending on
  the operational ErrorRecoveryLevel - all this diagram
  specifies is the dynamics of gracefully closing an active 
  iSCSI connection, perhaps replacing with a new connection.

- Consequent to the above and for general clarity, some 
  states have been renamed to reflect the "wait reason" better.

- Certain missing/incorrect transitions are now fixed -
  like the "close the session" Logout handling etc.

- I added some text on the first slide that describes the
  design philosophy behind the current model, perhaps also 
  can be called design assumptions.

I have only one (likely) open issue on my list.  I received
feedback from one reviewer that the _description_ of the diagrams 
is not "traditional" - for example, the current tabular format 
captures the transitions (each caused by a set of events) in 
a state-state matrix, but does not describe them in terms of 
an event-state matrix for each state (which would run into 
several pages).  The current description scheme seemed quite 
acceptable to myself (and also to Julian among others) - but 
I am open on this.  Please comment if you strongly feel about 
this issue.

Thanks! 
-- 
Mallikarjun 

Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions Organization
MS 5668	Hewlett-Packard, Roseville.
[email-masked]

---

From: [email-masked]
Date: Fri, 9 Nov 2001 22:31:56 -0500

Oops, "A bit tardy" refers to me taking a week to get
this message out, not to the time taken to produce these
diagrams.  Apologies for any confusion.  --David

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]
> Sent: Friday, November 09, 2001 10:29 PM
> To: [email-masked]; [email-masked]
> Subject: RE: iSCSI: new state diagrams for rev09
> 
> 
> A bit tardy, but I'd like to thank everyone whose efforts
> have contributed to these diagrams and explanations.  Getting
> error behavior completely specified is not easy, and very
> important to the overall specification of iSCSI.  Keep up
> the good work.
> 
> Many Thanks,
> --David 
> 
> > -----Original Message-----
> > From: Mallikarjun C. [mailto:[email-masked]]
> > Sent: Friday, November 02, 2001 1:33 PM
> > To: ips
> > Subject: iSCSI: new state diagrams for rev09
> > 
> > 
> > All:
> >

---

From: [email-masked]
Date: Fri, 9 Nov 2001 22:29:10 -0500

Many Thanks,
--David