RE: iFCP: A couple of iFCP questions

["Peglar, Robert" <robert_peglar@xiotech.com>]

Charles

You stated below...
> It's impossible to guarantee that the information returned in 
> response to a
> directory query won't silently become stale -- in spite of 
> state change
> notification.
> 
> Therefore, the requestor must assume that the data returned 
> may be stale by
> the time it is used to establish a session. It's the 
> responsibility of the
> session initiator to confirm that the desired endpoint was reached at
> session creation.

I agree.

However, when does this chase-one's-tail end?  If the requestor
can make no assumption about validity, i.e. all such responses
may be stale - how can unambiguous confirmation be achieved?  Does
this mean one must establish a class 1 connection between endpoints?

If no guarantees can be made about connectionless query responses
and their validity, then I think there may be a hole.

Thanks
Rob

Rob Peglar
Director, Storage Architecture
XIOtech Corporation
(314) 308-6983


> -----Original Message-----
> From: Charles Monia [mailto:cmonia@NishanSystems.com]
> Sent: Wednesday, January 03, 2001 7:29 PM
> To: Black_David@emc.com
> Cc: ips@ece.cmu.edu
> Subject: RE: iFCP: A couple of iFCP questions
> 
> 
> Hi David;
> 
> See below for comments.
> 
> > -----Original Message-----
> > From: Black_David@emc.com [mailto:Black_David@emc.com]
> > Sent: Wednesday, January 03, 2001 3:06 PM
> > To: jtseng@NishanSystems.com; Black_David@emc.com; ips@ece.cmu.edu
> > Subject: RE: A couple of iFCP questions
> > 
> > 
> > > I need to correct my prior message to state that "It is 
> > safe to discard
> > > a translation when there are no N_PORT sessions to the 
> > remote N_PORT...".
> > > The translation MAY be discarded when a PLOGO logout message
> > > that terminates the N_PORT session is detected.  This is 
> > what I meant
> > > in the original message.  Sorry about the confusion.
> > 
> > And I was a little sloppy in my language.  By "dropping the 
> > N_PORT session",
> > I meant the use of PLOGO to terminate the session.  After 
> > doing this, a
> > Fibre Channel device can use PLOGI to initiate a new 
> > connection to the same
> > target without checking with the fabric nameserver, because 
> > it can rely on
> > state change notification to tell it if a N_PORT ID has 
> > become invalid;
> > there
> > are FC devices that behave in this fashion.  Probing a remote N_PORT
> > to see if a session is alive won't catch this situation; 
> > something like a
> > state change notification to force the originator to go back 
> > to the fabric
> > nameserver is necessary.  Reliance on state change 
> > notification is also
> > why the WWPN of the target may not be checked when the new session
> > is set up.
> > 
> 
> It's impossible to guarantee that the information returned in 
> response to a
> directory query won't silently become stale -- in spite of 
> state change
> notification.
> 
> Therefore, the requestor must assume that the data returned 
> may be stale by
> the time it is used to establish a session. It's the 
> responsibility of the
> session initiator to confirm that the desired endpoint was reached at
> session creation.
> 
> I'd venture to say that this is true of any directory-driven 
> storage network
> in general.
> 
> <remainder deleted>
> 
> Charles
> Charles Monia
> Senior Technology Consultant
> Nishan Systems
> email: cmonia@nishansystems.com
> voice: (408) 519-3986
> fax:   (408) 435-8385
>