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    Re: iscsi : changes involving tgt portal group tag.



    John,
    
    I would have much preferred you addressing each of the 
    reasons I listed, but let me make one more attempt at this...
    
    1. Not specifying a *port* in the Login dialogue explicitly 
        is something I am concerned could cause surprises down
        the road.  Given that a Login is meant to establish an I_T
        nexus to a port (not to a node), I am rather surprised to see 
        the opposition simply because the proposal is coming late.
    
    2.  > manual reconfiguration (including a probable power down), that the Target
         > will maintain this key state ..
        This and a lot of your other text below dwells on the unlikelihood of
        target not maintaining the state - I agree with you.  My point is
        *not* that a target would, but the need to design the quickest and 
        most reliable way to communicate the loss of state back to the initiator.  
        I believe addition of TPGT to the Login Request PDU accomplishes that.
    
    With that said, if you (and possibly others) still disagree on the need to 
    add the TPGT, I request David Black to make a consensus call on this 
    when appropriate, and move on.
    
    Regards.
    --
    Mallikarjun
    
    Mallikarjun Chadalapaka
    Networked Storage Architecture
    Network Storage Solutions Organization
    Hewlett-Packard MS 5668 
    Roseville CA 95747
    cbm@rose.hp.com
    
    ----- Original Message ----- 
    From: "John Hufferd" <hufferd@us.ibm.com>
    To: "Mallikarjun C." <cbm@rose.hp.com>
    Cc: <ips@ece.cmu.edu>; <t10@t10.org>
    Sent: Tuesday, March 12, 2002 11:45 PM
    Subject: Re: iscsi : changes involving tgt portal group tag.
    
    
    > 
    > Perhaps we need to discover what causes the TPGT to change.   I think you
    > are saying that the IP address has somehow changed to a different portal
    > group.  Since the SCSI Port is not suppose to change its "effective" name,
    > if one was to change the IP address, you have a serious implicit change in
    > effect.
    > 
    > I think that means that the Target Storage Controller has been taken
    > offline and reconfigured.  Now if you believe that across this probable
    > manual reconfiguration (including a probable power down), that the Target
    > will maintain this key state (like persistent reserves) I think we are
    > talking about a small corner case, which few would really expect.
    > Especially since there is usually a normal quiesce and the session stopped
    > normally when that type of thing is planed to be done.  Further, one could
    > argue that if a Target chose to keep the state, it had the obligation to
    > keep the same mapping of IP address to TPG.  (And the target would have to
    > have more then one Target Portal Group.)  If one was to say that the outage
    > was not planned, then usually what happens in this type of a situation, the
    > HW is fixed and restarted, not reconfigured.
    > 
    > In fact, lets understand where the Portal gets its IP address.  It gets it
    > from the configuration software that comes with the controller.  In other
    > words it is the configuration software (perhaps with Administrative
    > assistance) that assigns IP address to the portals that make up a portal
    > group.  It seems like if they assign it to begin with, then there is an
    > obligation to keep the IP address bound to the TPG as long as a persistent
    > state exist with an LU that has a Nexus through that Portal group (SCSI
    > Port).  IP addresses do not automatically move with the physical
    > HBA/Portals.
    > 
    > If I was to write an Initiator, and the above possibility worried me, I
    > think I would have a time value, which if passed, I would always rediscover
    > the Node.  That value can be anything, so if "defaultTime2Wait" is not
    > good, I think I would pick another time, which reflected the possibility of
    > a manual change.
    > 
    > Bottom line, I do not think we need to have TPGT in the Login.
    > 
    > .
    > .
    > .
    > John L. Hufferd
    > Senior Technical Staff Member (STSM)
    > IBM/SSG San Jose Ca
    > Main Office (408) 256-0403, Tie: 276-0403,  eFax: (408) 904-4688
    > Home Office (408) 997-6136, Cell: (408) 499-9702
    > Internet address: hufferd@us.ibm.com
    > 
    > 
    > "Mallikarjun C." <cbm@rose.hp.com> on 03/12/2002 04:09:33 PM
    > 
    > To:    John Hufferd/San Jose/IBM@IBMUS
    > cc:    <ips@ece.cmu.edu>, <t10@t10.org>
    > Subject:    Re: iscsi : changes involving tgt portal group tag.
    > 
    > 
    > 
    > John,
    > 
    > > I do not see the absolute requirement for this TPGT in the Login.
    > 
    > That was my initial inclination as well, but now I believe there's value
    > in adding the TPGT to the Login Request PDU.
    > 
    > > it would be approprate to say that if the time for the Reconnect has been
    > > more then the "...Time2Wait" that the Initiator, if it cares about the
    > 
    > If I understand you correctly, you are suggesting that the DefaultTimeWait
    > value negotiated *for a session* should be used for decisions after the
    > end of that session.  I am afraid that it's a slippery slope...
    > 
    > OTOH, regardless of the proposed change, it would be reasonable to add text
    > that generally expresses this idea of potential volatility of portal
    > <->portal group
    > association in the iSCSI (or perhaps NDT) draft.
    > 
    > On to reasons that convinced me....
    > 
    > - An iSCSI session is an I_T nexus, and it is between an initiator *port*
    >    and a target *port*.  Login as a mechanism to instantiate/add to an
    >    iSCSI session should identify the target port in question, not just the
    >    target node.  The initiator port is currently identified in the Login
    >    dialogue
    >   (the InitiatorName text key and the ISID field), but not the target port.
    > 
    > - When there has been a portal group change for an IP address (portal) -
    >    meaning its TPGT had changed - it would be much more quicker to
    >    identify the fact and prevent an I_T nexus establishment by way of
    >    the TPGT in Login Request PDU.  The other option of having each
    >    LU assert its UA (REPORTED LUNS DATA HAS CHANGED) on
    >     the first command is prone to errors (see next bullet), and simply
    >     ineffcient.
    > 
    > - A target cold reset or a powercycle (possibly done after the portal group
    >    reconfiguration) would clear the aforementioned UA (but would assert
    >    a different UA for the power-on reset, but this generic UA gives no
    >    clue to initiators on the need to re-discover the target ports).
    > 
    > - At the moment, it is unclear to me if SPC-3 is mandating an "interlocked"
    >    style UA for the REPORTED LUNS DATA HAS CHANGED condition
    >    (though it seems like it... I will raise it only on t10 reflector under
    >    a different
    >     cover).  If that isn't the case, the UA interlock capability
    >     (T10/00-359) would
    >     need to deployed as well to realibly deal with this portal group
    >     reconfiguration.
    > 
    > > That would address the issue with out any protocol changes.
    > 
    > It is certainly a PDU change, but one can argue (successfully, I think)
    > that
    > it is not a "protocol" change per se -  since the implicit usage of TPGT so
    > far
    > (see my message to Julian earlier on this thread) is merely being turned
    > into
    > an explicit usage.
    > 
    > To summarize, I realize the sensitivity of changes this late but I believe
    > there
    > are reasonable grounds here.
    > 
    > Regards.
    > --
    > Mallikarjun
    > 
    > Mallikarjun Chadalapaka
    > Networked Storage Architecture
    > Network Storage Solutions Organization
    > Hewlett-Packard MS 5668
    > Roseville CA 95747
    > cbm@rose.hp.com
    > 
    > ----- Original Message -----
    > From: "John Hufferd" <hufferd@us.ibm.com>
    > To: "Mallikarjun C." <cbm@rose.hp.com>
    > Cc: <ips@ece.cmu.edu>; <t10@t10.org>
    > Sent: Tuesday, March 12, 2002 11:07 AM
    > Subject: Re: iscsi : changes involving tgt portal group tag.
    > 
    > 
    > >
    > > Mallikarjun,
    > > I do not see the absolute requirement for this TPGT in the Login.  I
    > think
    > > it would be approprate to say that if the time for the Reconnect has been
    > > more then the "...Time2Wait" that the Initiator, if it cares about the
    > > TPGT,  SHOULD perform a rediscovery.
    > >
    > > That would address the issue with out any protocol changes.
    > >
    > > .
    > > .
    > > .
    > > John L. Hufferd
    > > Senior Technical Staff Member (STSM)
    > > IBM/SSG San Jose Ca
    > > Main Office (408) 256-0403, Tie: 276-0403,  eFax: (408) 904-4688
    > > Home Office (408) 997-6136, Cell: (408) 499-9702
    > > Internet address: hufferd@us.ibm.com
    > >
    > >
    > > "Mallikarjun C." <cbm@rose.hp.com>@ece.cmu.edu on 03/12/2002 10:30:29 AM
    > >
    > > Sent by:    owner-ips@ece.cmu.edu
    > >
    > >
    > > To:    "Shailesh Manjrekar" <shaileshm@aarohicommunications.com>
    > > cc:    <ips@ece.cmu.edu>, <t10@t10.org>
    > > Subject:    Re: iscsi : changes involving tgt portal group tag.
    > >
    > >
    > >
    > > Shailesh,
    > >
    > > The failure resulting out of a TPGT mismatch (assuming we have the TPGT
    > in
    > > the Login Request PDU), would have to trigger a discovery
    > > (SendTargets/SLP/...)
    > > updating the initiator of the latest configuration.  This discovery
    > process
    > > is
    > > similar
    > > to the FCP ADISC process you refer to.
    > >
    > > Alternatively, if there has been a change in the LU view of  a given
    > target
    > > portal
    > > group tag (meaning that the TPGT would match correctly), the LUs in the
    > > view
    > > should have established UA with an ASC of REPORTED LUNS DATA HAS
    > > CHANGED since the SCSI port association has changed for the LUs.  This
    > > again
    > > should trigger a discovery process from the initiator.
    > >
    > > It seems to be that we are now sufficiently covered either way.
    > > --
    > > Mallikarjun
    > >
    > > Mallikarjun Chadalapaka
    > > Networked Storage Architecture
    > > Network Storage Solutions Organization
    > > Hewlett-Packard MS 5668
    > > Roseville CA 95747
    > > cbm@rose.hp.com
    > >
    > >
    > > ----- Original Message -----
    > > From: "Shailesh Manjrekar" <shaileshm@aarohicommunications.com>
    > > To: "'Mallikarjun C.'" <cbm@rose.hp.com>; "'Julian Satran'"
    > > <Julian_Satran@il.ibm.com>
    > > Cc: <ips@ece.cmu.edu>; <t10@t10.org>
    > > Sent: Monday, March 11, 2002 7:51 PM
    > > Subject: RE: iscsi : changes involving tgt portal group tag.
    > >
    > >
    > > > Hi,
    > > >
    > > > On a TPG reconfiguration or TPGT reassignment, shouldn't there be a
    > > > discovery followed by SCSI Inquiry and Report_LUNS which would make the
    > > > Initiator aware of this change? Can the  Async message - iscsi Event
    > > > Data notify the Initiator of the change, which would force an
    > discovery.
    > > > This would be similar to an ADISC for FCP. Because including the TPGT
    > in
    > > > the login would prevent inadvertent logins but would still not notify
    > > > the initiator of the changed configuration?
    > > >
    > > > Thanks,
    > > > Shailesh.
    > > > Aarohi Communications.
    > > > -----Original Message-----
    > > > From: owner-t10@t10.org [mailto:owner-t10@t10.org] On Behalf Of
    > > > Mallikarjun C.
    > > > Sent: Wednesday, March 06, 2002 10:17 AM
    > > > To: Julian Satran
    > > > Cc: ips@ece.cmu.edu; t10@t10.org
    > > > Subject: Re: iscsi : changes involving tgt portal group tag.
    > > >
    > > > * From the T10 Reflector (t10@t10.org), posted by:
    > > > * "Mallikarjun C." <cbm@rose.hp.com>
    > > > *
    > > > > The issue is that I am not sure that a target is checking today
    > > > anything -
    > > > > (adapter drivers may check oif in their realm they can give out a
    > > > TSID).
    > > > > Nothing else is needed.
    > > >
    > > > Target is required to derive the TPGT and use it in both cases of Login
    > > > -
    > > >      a) when TSID = 0, to ascertain if a session reinstatement needs to
    > > >          be effected for that TPGT.
    > > >      b) when TSID != 0, to ascertain the validity of TSID and add in
    > > >           the new connection to an existing session if it is valid for
    > > > that TPGT.
    > > > --
    > > > Mallikarjun
    > > >
    > > > Mallikarjun Chadalapaka
    > > > Networked Storage Architecture
    > > > Network Storage Solutions Organization
    > > > Hewlett-Packard MS 5668
    > > > Roseville CA 95747
    > > >
    > > > ----- Original Message -----
    > > > From: "Julian Satran" <Julian_Satran@il.ibm.com>
    > > > To: "Mallikarjun C." <cbm@rose.hp.com>
    > > > Cc: <ips@ece.cmu.edu>; <t10@t10.org>
    > > > Sent: Tuesday, March 05, 2002 11:56 PM
    > > > Subject: Re: iscsi : changes involving tgt portal group tag.
    > > >
    > > >
    > > > > The issue is that I am not sure that a target is checking today
    > > > anything -
    > > > > (adapter drivers may check oif in their realm they can give out a
    > > > TSID).
    > > > > Nothing else is needed. Does SCSI have to be aware of it? Perhaps but
    > > > > iSCSI certainly not. Does a "front-end" have to be - again probably
    > > > not
    > > > > the name identifies the node.
    > > > >
    > > > > Julo
    > > > >
    > > > >
    > > > >
    > > > >
    > > > > "Mallikarjun C." <cbm@rose.hp.com>
    > > > > 05-03-02 22:34
    > > > > Please respond to "Mallikarjun C."
    > > > >
    > > > >
    > > > >         To:     Julian Satran/Haifa/IBM@IBMIL
    > > > >         cc:     <ips@ece.cmu.edu>, <t10@t10.org>
    > > > >         Subject:        Re: iscsi : changes involving tgt portal
    > group
    > > > tag.
    > > > >
    > > > >
    > > > >
    > > > > Julian,
    > > > >
    > > > > Whatever methods a target is expected to use today to derive the
    > > > implicit
    > > > > TPGT to preclude a duplicate I-T nexus would work after the change as
    > > > > well,
    > > > > except the derived value needs to be compared against the (proposed)
    > > > > TPGT in the Login Request payload.
    > > > >
    > > > > Please comment if we're missing something.
    > > > >
    > > > > Regards.
    > > > > --
    > > > > Mallikarjun
    > > > >
    > > > > Mallikarjun Chadalapaka
    > > > > Networked Storage Architecture
    > > > > Network Storage Solutions Organization
    > > > > Hewlett-Packard MS 5668
    > > > > Roseville CA 95747
    > > > >
    > > > > ----- Original Message -----
    > > > > From: "Julian Satran" <Julian_Satran@il.ibm.com>
    > > > > To: "Mallikarjun C." <cbm@rose.hp.com>
    > > > > Cc: <ips@ece.cmu.edu>; <owner-ips@ece.cmu.edu>; "Santosh Rao"
    > > > > <santoshr@cup.hp.com>;
    > > > > <t10@t10.org>
    > > > > Sent: Monday, March 04, 2002 10:24 PM
    > > > > Subject: Re: iscsi : changes involving tgt portal group tag.
    > > > >
    > > > >
    > > > > > Has a decent target implementation and easy way of checking that
    > the
    > > > TPG
    > > > > > is correct?
    > > > > >
    > > > > > Julo
    > > > > >
    > > > > >
    > > > > >
    > > > > >
    > > > > > "Mallikarjun C." <cbm@rose.hp.com>
    > > > > > Sent by: owner-ips@ece.cmu.edu
    > > > > > 05-03-02 01:12
    > > > > > Please respond to "Mallikarjun C."
    > > > > >
    > > > > >
    > > > > >         To:     "Santosh Rao" <santoshr@cup.hp.com>,
    > > > <ips@ece.cmu.edu>
    > > > > >         cc:     <t10@t10.org>
    > > > > >         Subject:        Re: iscsi : changes involving tgt portal
    > > > group
    > > > > tag.
    > > > > >
    > > > > >
    > > > > >
    > > > > > Santosh and Jim,
    > > > > >
    > > > > > It appears a good idea to add in the portal group tag in the Login
    > > > > > Request header for a sanity check by the receiving target portal.
    > > > > >
    > > > > > I generally agree with Jim's comments that the duration of
    > > > persistence
    > > > > > of a portal group tag is intricately linked to the extent of portal
    > > > > > reconfiguration.
    > > > > > Not every target reconfiguration may result in a portal group tag
    > > > > > reassignment.
    > > > > > OTOH, some reconfigurations may be so extensive as to cause even a
    > > > node
    > > > > > name change.
    > > > > >
    > > > > > Some comments on Santosh's message -
    > > > > >
    > > > > > > "If a portal group is re-configured such that all its previously
    > > > > > > advertised network portals are no longer a part of the portal
    > > > group,
    > > > > > > then, the portal group tag (and thereby, the port
    > name/identifier)
    > > > > > > *MUST* be changed to indicate a new target port."
    > > > > >
    > > > > > I am not sure this solves the problem you're trying to get at.  If
    > > > none
    > > > > of
    > > > > > the earlier IP addresses can get an initiator to the SCSI target
    > > > port
    > > > > that
    > > > > > it
    > > > > > knew of (your scenario), it appears to me that it doesn't matter if
    > > > the
    > > > > > portal group tags are changed or not....A new discovery process
    > > > should
    > > > > > update the initiator of the changed portal addresses.
    > > > > >
    > > > > > I suggest the following text -
    > > > > >
    > > > > >    After a portal group reconfiguration which changed the view of
    > > > LUs
    > > > > >    for an initiator with a given set of privileges, the target MUST
    > > > > change
    > > > > >    the portal group tag that represents the reconfigured target
    > > > portal
    > > > > > group.
    > > > > >
    > > > > > > > Under these events, shouldn't all "open/active I_T_L traffic"
    > > > have
    > > > > > been
    > > > > > > > aborted, closed or otherwise ended?  So this shouldn't be an
    > > > issue
    > > > > at
    > > > > > all.
    > > > > > >
    > > > > > > On a session logout & re-login, it is not efficient/necessary to
    > > > close
    > > > > > > and re-open each LUN behind that target port, due to the fact
    > that
    > > > a
    > > > > > > target port may have hundred's of LUNs behind it.
    > > > > >
    > > > > > I agree with Jim on this one - there should be *no* open/active
    > > > I_T_L
    > > > > > nexus
    > > > > > traffic after a reconfiguration, targets can enforce this via
    > simple
    > > >
    > > > > iSCSI
    > > > > > means
    > > > > > (reject initiator advances to continue the session for
    > > > DefaultTime2Wait+
    > > > > > DefaultTime2Retain seconds).  In fact, Async logout request
    > requires
    > > > a
    > > > > > clean closure that implicitly aborts I/Os.
    > > > > >
    > > > > > What you're describing is typical O/S "LUN open" and "LUN close"
    > > > > > interactions.  I agree that they wouldn't have to be repeated, but
    > > > care
    > > > > > must be taken to ensure that new I/Os (on the new session after
    > > > > > reconfiguration)
    > > > > > are not delivered to the incorrect LUs.  It seems that the addition
    > > > of
    > > > > > TPGT in the login header and the proposed new text (above) would
    > > > take
    > > > > > care of this.
    > > > > >
    > > > > > Regards.
    > > > > > --
    > > > > > Mallikarjun
    > > > > >
    > > > > > Mallikarjun Chadalapaka
    > > > > > Networked Storage Architecture
    > > > > > Network Storage Solutions Organization
    > > > > > Hewlett-Packard MS 5668
    > > > > > Roseville CA 95747
    > > > > >
    > > > > > ----- Original Message -----
    > > > > > From: "Santosh Rao" <santoshr@cup.hp.com>
    > > > > > To: <ips@ece.cmu.edu>
    > > > > > Cc: <t10@t10.org>
    > > > > > Sent: Monday, March 04, 2002 10:40 AM
    > > > > > Subject: Re: iscsi : changes involving tgt portal group tag.
    > > > > >
    > > > > >
    > > > > > > * From the T10 Reflector (t10@t10.org), posted by:
    > > > > > > * Santosh Rao <santoshr@cup.hp.com>
    > > > > > > *
    > > > > > > Jim,
    > > > > > >
    > > > > > > I agree that a "complete re-configuration" of a target port can
    > > > result
    > > > > > > in a new port name & port identifier. However, the tricky part is
    > > > the
    > > > > > > definition of a "complete re-configuration of an iscsi target
    > > > port",
    > > > > due
    > > > > > > to the concepts of portal groups involving multiple network
    > > > portals.
    > > > > > >
    > > > > > > For example, if a portal group (aka, an iscsi target port) were
    > to
    > > > be
    > > > > > > re-configured to include a new network portal [moved from another
    > > > > portal
    > > > > > > group], then, the target port itself has not changed, since it is
    > > > > still
    > > > > > > accessible through its previously used network portals. What has
    > > > > changed
    > > > > > > is the individual network portal that has moved from 1 target
    > port
    > > > to
    > > > > > > another.
    > > > > > >
    > > > > > > Hence, it is sufficient, in this case, to maintain persistence of
    > > > the
    > > > > > > target port name/identifier, without requiring any change in port
    > > > > > > name/identifier. By requiring initiators to send the intended
    > TPGT
    > > >
    > > > > (scsi
    > > > > > > target port name/identifier) along with the login request, this
    > > > allows
    > > > > > > the target port to detect that the network portal is being
    > > > accessed to
    > > > > > > connect to a different target port and it can reject the login.
    > > > > > >
    > > > > > > It may be helpful to call out the specific case when a port
    > > > > > > name/identifier MUST change. How about something like :
    > > > > > >
    > > > > > > "If a portal group is re-configured such that all its previously
    > > > > > > advertised network portals are no longer a part of the portal
    > > > group,
    > > > > > > then, the portal group tag (and thereby, the port
    > name/identifier)
    > > > > > > *MUST* be changed to indicate a new target port."
    > > > > > >
    > > > > > > This would allow access to the target port through its un-altered
    > > > > > > network portals to continue un-disrupted. More comments inline,
    > in
    > > > > > > response to some of your queries.
    > > > > > >
    > > > > > > Thanks,
    > > > > > > Santosh
    > > > > > >
    > > > > > > NOTE : In this discussion target port and target portal group are
    > > > used
    > > > > > > to imply the same entity, within a target node.
    > > > > > >
    > > > > > >
    > > > > > > Jim Hafner wrote:
    > > > > > >
    > > > > > > > SAM-2 requires scsi port names to be persistent and
    > > > > world-wide-unique.
    > > > > > > > (SAM-2 Rev 22 Section 4.7.7). Quoting from SAM-2 :
    > > > > > > >
    > > > > > > > "A scsi port name shall never change and may be used to
    > > > persistently
    > > > > > > > identify a scsi initiator port or target port...".
    > > > > > > >
    > > > > > > > <JLH>
    > > > > > > > There are different ways that one can interpret this
    > > > "persistent"
    > > > > > rule. The
    > > > > > > > intent was that names shouldn't change over time when
    > > > *identifying
    > > > > the
    > > > > > same
    > > > > > > > object*.   What that means is that if the object changes (in
    > any
    > > > > > > > discernable way), then the name should change.  So, the object
    > > > can
    > > > > > move to
    > > > > > > > a different piece of hardware, but it can still be named the
    > > > same
    > > > > way.
    > > > > >  If
    > > > > > > > the object changes, e.g., in this case, reconfigures as a
    > > > different
    > > > > > set of
    > > > > > > > network portals with different addressing elements, then I
    > would
    > > >
    > > > > think
    > > > > > that
    > > > > > > > the name should change as well.   That's all the persistence
    > one
    > > > > > really
    > > > > > > > needs.
    > > > > > > >
    > > > > > > > I'm not sure what that implies about your recommendation.  I
    > > > don't
    > > > > see
    > > > > > any
    > > > > > > > problem with it, either.
    > > > > > > > </JLH>
    > > > > > >
    > > > > > > I think we may be in agreement. (See reasoning above).
    > > > > > >
    > > > > > >
    > > > > > > >
    > > > > > > > The rationale for (2) is :
    > > > > > > > --------------------------
    > > > > > > > Consider an initiator node establishing multiple sessions to a
    > > > scsi
    > > > > > tgt
    > > > > > > > port, with each session established to a subset of the network
    > > > > portals
    > > > > > > > within the tgt portal group.
    > > > > > > >
    > > > > > > > Consider an iscsi transport event involving the
    > re-configuration
    > > > of
    > > > > > > > target portal groups on the iscsi target node. This may be
    > > > preceeded
    > > > > > by
    > > > > > > > the iscsi sessions seeing an async message "target requests
    > > > logout",
    > > > > > > > followed by session logout, portal group re-configuration, and
    > > > then,
    > > > > > the
    > > > > > > > initiator re-establishes sessions.
    > > > > > > >
    > > > > > > > Across a transport event that results in such session
    > > > termination
    > > > > and
    > > > > > > > re-establishment, the initiator needs to authenticate that it
    > is
    > > >
    > > > > still
    > > > > > > > speaking to the same [i]scsi target port, in order to ensure
    > > > that
    > > > > any
    > > > > > > > open/active I-T-L nexus traffic on that session is not
    > > > incorrectly
    > > > > > > > routed to a wrong LUN after such a transport event.
    > > > > > >
    > > > > > > > <JLH>
    > > > > > > > Under these events, shouldn't all "open/active I_T_L traffic"
    > > > have
    > > > > > been
    > > > > > > > aborted, closed or otherwise ended?  So this shouldn't be an
    > > > issue
    > > > > at
    > > > > > all.
    > > > > > >
    > > > > > > On a session logout & re-login, it is not efficient/necessary to
    > > > close
    > > > > > > and re-open each LUN behind that target port, due to the fact
    > that
    > > > a
    > > > > > > target port may have hundred's of LUNs behind it.
    > > > > > >
    > > > > > > All outstanding I/Os need to be aborted. Once the session is
    > > > > > > re-established [and the target port is authenticated to be the
    > > > same],
    > > > > > > further I/O traffic can be resumed without requiring the SCSI ULP
    > > > to
    > > > > > > close and re-open each LUN. Some transport specific clearing
    > > > effects
    > > > > may
    > > > > > > have occurred, which may require additional LUN level activity,
    > in
    > > >
    > > > > some
    > > > > > > cases.
    > > > > > >
    > > > > > > (There are analogies to the above model in FCP & SRP, which
    > > > > authenticate
    > > > > > > port name/identifier on login, allowing I/O resumption after
    > > > session
    > > > > > > termination and re-establishment.)
    > > > > > >
    > > > > > >
    > > > > > > > To prevent such authentication issues, iscsi can send the iscsi
    > > > > target
    > > > > > > > port identifier (portal group tag) explicitly in the login
    > > > request,
    > > > > > and
    > > > > > > > the login can be rejected by the target on a portal group tag
    > > > > > mis-match.
    > > > > > > > (if the network portal does not belong to the addressed portal
    > > > group
    > > > > > > > tag).
    > > > > > > > <JLH>
    > > > > > > > Did you mean for the initiator to send this TPGT?
    > > > > > > > </JLH>
    > > > > > >
    > > > > > > Yes. The initiator login request must include the target portal
    > > > group
    > > > > > > tag, thus identifying the target port to which a session is being
    > > > > > > established.
    > > > > > >
    > > > > > > Login currently carries no addressing information, since the
    > > > > addressing
    > > > > > > is implicit, based on the TCP connection in use. The problem with
    > > > this
    > > > > > > approach is that the login implicitly addresses a network portal,
    > > > and
    > > > > > > not the target port. As seen in the earlier example, the
    > > > association
    > > > > of
    > > > > > > network portal <-> target port can change, and such changes can
    > be
    > > > > > > detected, if the initiator were to explicitly identify the target
    > > > port
    > > > > > > being logged into.
    > > > > > >
    > > > > > > --
    > > > > > > ##################################
    > > > > > > Santosh Rao
    > > > > > > Software Design Engineer,
    > > > > > > HP-UX iSCSI Driver Team,
    > > > > > > Hewlett Packard, Cupertino.
    > > > > > > email : santoshr@cup.hp.com
    > > > > > > Phone : 408-447-3751
    > > > > > > ##################################
    > > > > > > *
    > > > > > > * For T10 Reflector information, send a message with
    > > > > > > * 'info t10' (no quotes) in the message body to majordomo@t10.org
    > > > > > >
    > > > > >
    > > > > >
    > > > > >
    > > > >
    > > > >
    > > > >
    > > > >
    > > > *
    > > > * For T10 Reflector information, send a message with
    > > > * 'info t10' (no quotes) in the message body to majordomo@t10.org
    > > >
    > > >
    > >
    > >
    > >
    > >
    > >
    > 
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Last updated: Wed Mar 13 21:18:31 2002
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