RE: iFCP: A couple of iFCP questions

[Charles Monia <cmonia@NishanSystems.com>]

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