RE: Keep-alive traffic (was iSCSI: more on StatRN)

[Charles Monia <cmonia@NishanSystems.com>]

Hi:

The scenario I had in mind was the minimalist one where a device, say in a
storage utlity environment, wants to do garbage collection on iSCSI
sessions.  In that case, the device might send some sort of iSCSI "ping"
before it decides to preemptively close a dormant iSCSI session.  The sort
of "ping" I had in mind would be subject to the same security checks that
apply to any other iSCSI transaction.

Is this rocket science? If so, I don't believe it's worth a whole lot of
further discussion.

Charles
> -----Original Message-----
> From: Douglas Otis [mailto:dotis@sanlight.net]
> Sent: Tuesday, October 31, 2000 10:17 AM
> To: Charles Monia; ips@ece.cmu.edu
> Subject: RE: Keep-alive traffic (was iSCSI: more on StatRN)
> 
> 
> Charles,
> 
> You may wish to be less nebulous about when a probe would be used.  By
> mandating probes when no communication is occurring while 
> status is pending
> allows tight timeouts to enforced.  Three probes sent every 
> 10 seconds will
> provide a connection failure at the point where a forth probe 
> would be sent
> with still no acknowledgement as example.  During idle 
> periods, a keepalive
> recommendation should be adequate.
> 
> Doug
> 
> > Hi:
> >
> > I assume the objection is only to mandatory keep alive.
> >
> > In high-availabilty scenarios, pinging of some sort goes on all
> > the time to
> > detect when an otherwise long-dormant node loses 
> connectivity or becomes
> > brain-dead.
> >
> > I assume the issue is detection and cleanup of dead iSCSI
> > sessions.  In that
> > case, why not have the node issue a ping to a dormant 
> session when it has
> > reason to believe that the session may be blown.
> >
> > Charles
> > > -----Original Message-----
> > > From: Stephen Bailey [mailto:steph@cs.uchicago.edu]
> > > Sent: Monday, October 30, 2000 3:25 PM
> > > To: ips@ece.cmu.edu
> > > Subject: Re: iSCSI: more on StatRN
> > >
> > >
> > > > What probe rate on a waiting response without other 
> confirmation of
> > > > connection happening would you specify?
> > >
> > > Upon further reflection I'm not sure I analyzed the situation
> > > correctly.  I know you all think everything through 
> completely before
> > > you start typing, so you can just stone me right now for 
> not doing the
> > > same.
> > >
> > > I don't see why free running keep-alives are necessary at all in
> > > iSCSI.
> > >
> > > Targets only care if the connection is lost when they are 
> returning
> > > something to the initiator.  Attempting to send anything 
> from target
> > > to initiator will detect a lost connection, so a keep-alive is not
> > > necessary.
> > >
> > > Initiators will maintain task timers on outstanding SCSI 
> operations,
> > > and when a task timer expires, whatever action the 
> initiator performs
> > > (Abort Task exchange, ping, whatever) will discover the lost
> > > connection.  Again, no keep-alive is necessary.
> > >
> > > Steph
> > >
> >
>