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

["Douglas Otis" <dotis@sanlight.net>]

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
> >
>