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    Re: iSCSI : target session login behaviour



    "Mudaliar, Hari" wrote:
    
    >         I am assuming that you are referring to the creation of a new
    > session with TSID=0 in your example below. Take the case of an initiator I1
    > who has established a session with a target with an ISID=ISID1. What if a
    > second initator I2 tries to login to the same target with ISID1? The target
    > cannot decide to logout the first initiator (who already has a session
    > established with ISID1) as suggested by you. 
    
    Hari,
    
    You may want to take a second look at my mail. It specifically refers to
    the problem in the context of a given (Initiator Name, ISID). Your
    example above does not fall under that category. A 2nd initiator using
    the same ISID would have a different Initiator Name. (a.k.a initiator
    WWUI).
    
    The problem raised is in the context of an existing session for a given
    (Initiator Name, ISID). How does a target deal with a second session
    login received for the same (Initiator Name, ISID) with a NULL TSID ?
    
    >         Also, depending on implementation, the target may realize that the
    > TCP connections for a session were lost (using Keep-Alives or iSCSI NOPs
    > etc.) when the initiator rebooted thus terminating the session. By the time
    > a new login from the same initiator is received, the old session info may
    > have been cleared.
    
    Then again, it may not. There's 2 aspects to this issue :
    1) Successful session re-logins from the rebooted host.
    2) Garbage collection and cleanup of the old session resources.
    
    (1) is a more serious issue, since the target MUST NOT reject the login
    based on a pre-existing active session for a given (Initiator Name,
    ISID).
    
    (2) is handled through garbage collection algorithms, but implementation
    of the proposal would help accelerate the release of stale session
    resources.
    
    - Santosh
    
    
    > 
    > -----Original Message-----
    > From: Santosh Rao [mailto:santoshr@cup.hp.com]
    > Sent: Wednesday, April 25, 2001 11:19 AM
    > To: IPS Reflector
    > Subject: iSCSI : target session login behaviour
    > 
    > All,
    > 
    > How should a target respond when it receives a session login  [on a new
    > TCP connection] with the same (ISID, Initiator Name) as a session
    > already active at the target.
    > 
    > Does such a login request imply :
    > 
    > 1) the target should perform implicit logout and re-login of the session
    > identified by (ISID, initiator name) ?
    > 
    > 2) Or does this result in the target responding to the session login
    > with :
    > a login response with status class of non-zero indicating target is
    > rejecting the login ?
    > 
    > [The draft does not describe target behaviour for this scenario.]
    > 
    > iSCSI session login semantics should explicitly state that the above
    > scenario will result in case (1) above. i.e. when a target sees a
    > session login for a given (ISID, initiator name), it MUST treat this as
    > an implicit logout of any previous session active at the target for that
    > (ISID, initiator name) and then, establish a new session.
    > 
    > This is required because the above scenario can typically occur when an
    > initiator reboots without having performed a session logout on all
    > active sessions.(system did not perform an orderly shutdown).
    > 
    > As a side note, the iSCSI draft Status Class/Codes could do with a misc
    > error category along the lines of the FC "No additional Explantion"
    > reason explantion. This would help deal with error conditions that don't
    > come under the listed category.
    > 
    > - Santosh
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    title:Software Design Engineer
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    fn:Santosh Rao
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Last updated: Tue Sep 04 01:04:52 2001
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