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    Re: is TargetName always mandatory or not?



    John,
         Section 3.12.9 of the spec reads:
    
            The TSID is the target assigned tag for a session with a specific
            named initiator that, together with the ISID uniquely identifies a
            session with that initiator.
    
         So according to that, TSID + ISID + InitiatorName must be enough
    information for a target to uniquely idenfity a session, so mapping TSID to
    target portal group ID won't always work (see my other note addressed to
    Jim for an example of where it won't).
         After thinking about this for a while, I've come to the same
    conclusion as you (that a target should compare ISID + InitiatorName +
    TargetName + target portal group to uniquely identify a session), but from
    a different angle.
         My reasoning:  Since there is a 1-1 correspondence between an I_T
    nexus and a session, if you can identify the nexus, you've identified the
    session, and vice versa.  Since 3.12.9 says that TSID + ISID +
    InitiatorName must uniquely identify a session, then TSID must be an alias
    for TargetName + target portal group ID, since (ISID + InitiatorName +
    TargetName + portal group ID) uniquely identifies a nexus.  In my opinion,
    that aliasing only complicates (and confuses!) the protocol and should be
    done away with.  If TargetName were required on every initial login
    request, then the target could compare (ISID + InitiatorName + TargetName +
    portal group) to determine a session match, and forget about TSID entirely.
    In that case, there is no need for TSID, except to flag whether the login
    request is to create a new session or to add a new connection to an
    existing session (i.e. indicate leading login), in which case it could be
    dropped and replaced with a single bit.
    
    To eliminate TSID, I believe the following changes would be needed:
    - Eliminate TSID from login request and login response
    - Use one of the bits in byte 1 of login request to indicate a leading
    login, and update any text that refers to TSID=0 to refer to this bit
    - Define session to be equivalent to I_T nexus (not "loosely equivalent
    to")
    - Define SSID/session ID to be the same as the I_T nexus identifier
    - Remove the "LO" from TargetName
    - If it hasn't already been done, remove the "LO" from InitiatorName
    
    Comments?
    
    Andre Asselin
    IBM ServeRAID Software Development
    Research Triangle Park, NC
    
    
    
                                                                                                                                          
                        John Hufferd                                                                                                      
                                             To:     Andre Asselin/Raleigh/IBM                                                            
                        10/31/2001           cc:     ips@ece.cmu.edu                                                                      
                        06:32 PM             From:   John Hufferd/San Jose/IBM@IBMUS                                                      
                                             Subject:     Re: is TargetName always mandatory or not?(Document link: Andre Asselin)        
                                                                                                                                          
                                                                                                                                          
                                                                                                                                          
                                                                                                                                          
                                                                                                                                          
                                                                                                                                          
    
    
    
    Andre,
    TSID, and therefore SSID is a handle that can be use to queue stuff within
    the scope of the Initiator Node and Target Node.  The target can use what
    ever it wants in this field.  Some Folks might want to use the TSID to be
    the Portal Group Tag and I think then it might be unique.   But even then
    only within the InitiatorName+ISID Space.  Anyway, you need to think of it
    only as a handle.  Also since most folks will not have 64k Sessions into
    their box, some (most?) implementations  might find it unique.  But it is
    not unique in the Architecture.
    
    Now the important thing is that, as things stand now, the Login needs the
    InitiatorName, and the TargetName on the Initial Login of ALL Connections
    in order to uniquely identify secondary Connections to the Original
    Connection of the Session.
    
    Does that seem correct to you and others on the Reflector?
    
    .
    .
    .
    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
    Internet address: hufferd@us.ibm.com
    
                                                           
                    Andre Asselin                          
                    10/31/2001 03:00 PM                    
                                                           
                                                           
    
    
    
    To:   John Hufferd/San Jose/IBM@IBMUS
    cc:   ips@ece.cmu.edu
    From: Andre Asselin/Raleigh/IBM@IBMUS
    Subject:  Re: is TargetName always mandatory or not?  (Document link: John
          Hufferd)
    
    John,
         WHOOPS!  I was wrong; you are absolutely right that the spec says
    "TargetName" and not "TSID".  When I was reading through it, I saw
    "TargetName", but read to myself "TSID".  Apologies...
         In my defense (confusion?), however, 3.12.9 says TSID rather than
    TargetName is used to uniquely identify a session.  Going by that, SSID +
    InitiatorName must be enough to uniquely identify a session.
    
         Jim Hafner pointed out to me that the I_T nexus is identified by one
    thing and the session is identified by another.  If the two must have a 1-1
    mapping in iSCSI, why are there two different identifiers?  Why not just
    use the current definition of the I_T nexus to uniquely identify both the
    nexus and session (i.e. get rid of TSID)?
    
    Andre Asselin
    IBM ServeRAID Software Development
    Research Triangle Park, NC
    
    
    
                                                                                                                                          
                        John Hufferd                                                                                                      
                                             To:     Andre Asselin/Raleigh/IBM@IBMUS                                                      
                        10/31/2001           cc:     ips@ece.cmu.edu                                                                      
                        04:42 PM             From:   John Hufferd/San Jose/IBM@IBMUS                                                      
                                             Subject:     Re: is TargetName always mandatory or not?(Document link: Andre Asselin)        
                                                                                                                                          
                                                                                                                                          
                                                                                                                                          
                                                                                                                                          
                                                                                                                                          
                                                                                                                                          
    
    
    
    Andre,
    I looked again through the document and No where could I find a statement
    that you claimed as "a nexus, and therefore an iSCSI session, is uniquely
    identified by the InitiatorName, ISID, TSID, and portal group tag".  It is
    the InitiatorName, ISID, TSID, with the TargetName and PortalGroup.
    
    Please point out to me in the Spec (8 or above), where  I can find your
    statement on I_T Nexus.
    
    I did find the following (please ignore for this conversation the "i" and
    't" stuff):
    
    "- Session: The group of TCP connections that link an initiator with a
    target, form a session (loosely equivalent to a SCSI I-T nexus). TCP
    connections can be added and removed from a session. Across all connections
    within a session, an initiator sees one "target image".  "
    
    " - I_T nexus: According to [SAM2], the I_T nexus is a relationship between
    a SCSI Initiator Port and a SCSI Target Port. For iSCSI, this relationship
    is a session, defined as a relationship between an iSCSI Initiator's end of
    the session (SCSI Initiator Port) and the iSCSI Target's Portal Group. The
    I_T nexus can be identified by the conjunction of the SCSI port names; that
    is, the I_T nexus identifier is the tuple (iSCSI Initiator Name + 'i'+
    ISID, iSCSI Target Name + 't'+ Portal Group Tag). NOTE: The I_T nexus
    identifier is not equal to the session identifier (SSID).  "
    
    I have not found a place where Session ID is tied to the TSID.
    
    Hence my comment that we also need to have the TargetName in the Initial
    Login on all Connections.
    
    
    
    .
    .
    .
    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
    Internet address: hufferd@us.ibm.com
    
    
    Andre Asselin/Raleigh/IBM@IBMUS@ece.cmu.edu on 10/31/2001 10:40:55 AM
    
    Sent by:  owner-ips@ece.cmu.edu
    
    
    To:   ips@ece.cmu.edu
    cc:   John Hufferd/San Jose/IBM@IBMUS
    Subject:  Re: is TargetName always mandatory or not?
    
    
    
    John & Julian,
         How about this for the section 5 text:
    
    The initial Login request of the first connection of a session (leading
    login) MUST include the InitiatorName key=value pair. The initial login
    request
    of the leading Login MAY also include the SessionType key=value pair, in
    which case if the SessionType is not "discovery", then the initial login
    request
    MUST also include the key=value pair TargetName.
    
    John,
         I disagree with your second statement: I don't see any way you could
    have 2 different sessions established within the same portal group with the
    same InitiatorName, ISID, and TSID.  The spec. says that a nexus, and
    therefore an iSCSI session, is uniquely identified by the InitiatorName,
    ISID, TSID, and portal group tag.  There is no mention of TargetName
    contributing to the identificaiton of a session.  In my opinion, a
    non-leading connection should NOT have the TargetName, since it doesn't
    contribute anything.
    
    Andre Asselin
    IBM ServeRAID Software Development
    Research Triangle Park, NC
    
    
    
    
                        John
                        Hufferd/San          To:     Julian
    Satran/Haifa/IBM@IBMIL
                        Jose/IBM@IBMUS       cc:     ips@ece.cmu.edu
                        Sent by:             Subject:     Re: is TargetName
    always mandatory or not?
                        owner-ips@ece.
                        cmu.edu
    
    
                        10/31/2001
                        04:20 AM
    
    
    
    
    
    
    Julian,
    I think the TargetName should be included on the Initial Login Request on
    the Leading Login.  It seem strange to permit the Authentication functions
    to proceed if perhaps the intended Target is different then the one doing
    the Authentication.  The way it currently is written, you could pass all
    the Security test and then find out just before going into Full Function
    Phase, that it was intended for some other Target.  Seems like a waste.
    
    My I think that TargetName should also be on all connections on the Initial
    Login Request.  Here is my thinking:
    
    The SSID (ISID+TSID) is unique only with regards to a Specific Initiator
    and Target Node Pair.  It is therefore not clear that just knowing the SSID
    and InitiatorName is enough to understand what session the subsequent
    connections are being attached to.  And it is possible that the CID could
    be also overlapped with another session.
    
    Therefore, I think it make since to determine all this on the initial Login
    on every Connection, so you know at the beginning what values can be
    negotiated, or that are being set to the right Session.
    
    .
    .
    .
    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
    Internet address: hufferd@us.ibm.com
    
    
    Julian Satran/Haifa/IBM@IBMIL@ece.cmu.edu on 10/30/2001 11:33:50 PM
    
    Sent by:  owner-ips@ece.cmu.edu
    
    
    To:   ips@ece.cmu.edu
    cc:
    Subject:  Re: is TargetName always mandatory or not?
    
    
    
    It is the leading login:
    
    The section 5 paragraph will read:
    
    The initial Login request of the first connection of a session (leading
    login) MUST include the InitiatorName key=value pair. The leading Login
    request MAY also include the SessionType key=value pair in which case if
    the SessionType is not "discovery" then the leading Login Request MUST
    also include the key=value pair TargetName.
    
    Julo
    
    
    
    
    Andre Asselin/Raleigh/IBM@IBMUS
    Sent by: owner-ips@ece.cmu.edu
    31-10-01 02:08
    Please respond to Andre Asselin
    
    
            To:     "IPS Reflector (E-mail)" <ips@ece.cmu.edu>
            cc:
            Subject:        is TargetName always mandatory or not?
    
    
    
         In section 5 of the spec, it says "If the SessionType is not
    "discovery" then the initial Login Request MUST also include the key=value
    pair TargetName.".  However, in Appendix D, the description for TargetName
    says it is Leading Only.
         Should TargetName not be Leading Only, or should the text in section
    5
    say that TargetName must be in the initial Login Request of a leading
    connection?
    
    Andre Asselin
    IBM ServeRAID Software Development
    Research Triangle Park, NC
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    


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