iscsi : changes involving tgt portal group tag.

Mallikarjun C. cbm at rose.hp.com
Wed Mar 13 11:51:38 PST 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "Mallikarjun C." <cbm at rose.hp.com>
*
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 at rose.hp.com

----- Original Message ----- 
From: "John Hufferd" <hufferd at us.ibm.com>
To: "Mallikarjun C." <cbm at rose.hp.com>
Cc: <ips at ece.cmu.edu>; <t10 at 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 at us.ibm.com
> 
> 
> "Mallikarjun C." <cbm at rose.hp.com> on 03/12/2002 04:09:33 PM
> 
> To:    John Hufferd/San Jose/IBM at IBMUS
> cc:    <ips at ece.cmu.edu>, <t10 at 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 at rose.hp.com
> 
> ----- Original Message -----
> From: "John Hufferd" <hufferd at us.ibm.com>
> To: "Mallikarjun C." <cbm at rose.hp.com>
> Cc: <ips at ece.cmu.edu>; <t10 at 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 at us.ibm.com
> >
> >
> > "Mallikarjun C." <cbm at rose.hp.com>@ece.cmu.edu on 03/12/2002 10:30:29 AM
> >
> > Sent by:    owner-ips at ece.cmu.edu
> >
> >
> > To:    "Shailesh Manjrekar" <shaileshm at aarohicommunications.com>
> > cc:    <ips at ece.cmu.edu>, <t10 at 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 at rose.hp.com
> >
> >
> > ----- Original Message -----
> > From: "Shailesh Manjrekar" <shaileshm at aarohicommunications.com>
> > To: "'Mallikarjun C.'" <cbm at rose.hp.com>; "'Julian Satran'"
> > <Julian_Satran at il.ibm.com>
> > Cc: <ips at ece.cmu.edu>; <t10 at 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 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of
> > > Mallikarjun C.
> > > Sent: Wednesday, March 06, 2002 10:17 AM
> > > To: Julian Satran
> > > Cc: ips at ece.cmu.edu; t10 at t10.org
> > > Subject: Re: iscsi : changes involving tgt portal group tag.
> > >
> > > * From the T10 Reflector (t10 at t10.org), posted by:
> > > * "Mallikarjun C." <cbm at 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 at il.ibm.com>
> > > To: "Mallikarjun C." <cbm at rose.hp.com>
> > > Cc: <ips at ece.cmu.edu>; <t10 at 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 at rose.hp.com>
> > > > 05-03-02 22:34
> > > > Please respond to "Mallikarjun C."
> > > >
> > > >
> > > >         To:     Julian Satran/Haifa/IBM at IBMIL
> > > >         cc:     <ips at ece.cmu.edu>, <t10 at 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 at il.ibm.com>
> > > > To: "Mallikarjun C." <cbm at rose.hp.com>
> > > > Cc: <ips at ece.cmu.edu>; <owner-ips at ece.cmu.edu>; "Santosh Rao"
> > > > <santoshr at cup.hp.com>;
> > > > <t10 at 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 at rose.hp.com>
> > > > > Sent by: owner-ips at ece.cmu.edu
> > > > > 05-03-02 01:12
> > > > > Please respond to "Mallikarjun C."
> > > > >
> > > > >
> > > > >         To:     "Santosh Rao" <santoshr at cup.hp.com>,
> > > <ips at ece.cmu.edu>
> > > > >         cc:     <t10 at 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 at cup.hp.com>
> > > > > To: <ips at ece.cmu.edu>
> > > > > Cc: <t10 at t10.org>
> > > > > Sent: Monday, March 04, 2002 10:40 AM
> > > > > Subject: Re: iscsi : changes involving tgt portal group tag.
> > > > >
> > > > >
> > > > > > * From the T10 Reflector (t10 at t10.org), posted by:
> > > > > > * Santosh Rao <santoshr at 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 at cup.hp.com
> > > > > > Phone : 408-447-3751
> > > > > > ##################################
> > > > > > *
> > > > > > * For T10 Reflector information, send a message with
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> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > *
> > > * For T10 Reflector information, send a message with
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> > >
> > >
> >
> >
> >
> >
> >
> 
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> 
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