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    RE: iscsi : originating & responding parties in login.



    Santosh-
    
    I agree with you. The initiator will (should) always be the originator
    either
    by explicitly sending the key value or not sending and thereby implicitly
    negotiating
    for the default value. This simplifies a lot, in  my opinion.
    
    Julian-  is there any
    specific reason, why would an initiator explicity a value even if it is
    default? Can
    the target not determine that by sending no keys, initiator is actually
    sending a default
    value? Am I missing something otherwise?
    
    Thanks
    
    Deva
    
    
    -----Original Message-----
    From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
    Santosh Rao
    Sent: Wednesday, October 03, 2001 2:24 PM
    To: Julian Satran
    Cc: IPS Reflector
    Subject: Re: iscsi : originating & responding parties in login.
    
    
    Julian Satran wrote:
    
    > Julian Satran wrote:
    >
    > > As negotiations can start at either initiator or target the
    > originator
    > > the one that starts the negotiation.
    >
    > Julian,
    >
    > OTOH, since the initiator did offer a value (the default value), is'nt
    > it always the originator ? In which case [other than a target vendor
    > specific proprietary key] would an operational negotiation start at
    > the
    > target ?
    > +++ offering a value is an active thing. Defaults and previous values
    > don't count. +++
    
    
    This is intriguing. If an initiator explicitly sent a key value (albeit,
    with the key initialized to the default), the initiator is considered
    the originator. However, if the initiator chose to not send the key
    explicitly, but use the default, it then becomes the responder. [if
    target does not accept the default.]
    
    This leads to different on-the-wire login behaviour if the initiator
    chose to use defaults instead of sending those same key values
    explicitly. It also causes an additional dummy login hand-shake for no
    purpose.
    
    Thus, in the case where initiator wants to use, say, FirstBurstSize=128
    & target allows FirstBurstSize to be 8, then, the behaviour on the wire
    is different depending on whether the initiator used the default or
    explicitly sent the key.
    
    Case 1) Initiator sends the default value as an explicit offering
    ------------------------------------------------------------------
    I -> T : FirstBurstSize=128 (initiator is the originator)
    	 (CSG=Operational, NSG=FFP). T=1
    
    T -> I : FirstBurstSize=8 (target responds with lower value it
    supports.)
    	 (CSG=Operational, NSG=FFP). T=1
    
    Negotiation ends at initiator with both sides picking FirstBurstSize=8.
    Single login handshake.
    
    Case 2) Initiator does not send the key. (default is in use).
    -------------------------------------------------------------
    I -> T : (no key sent). (defaults to 128.)
    	  (CSG=Operational , NSG=FFP). T=1
    
    T -> I : FirstBurstSize=8
    	 (CSG=Operational, NSG=Operational). T=0
    
    I -> T : FirstBurstSize=128 (initiator explicitly resends the default
    !).
    	(CSG=Operational, NSG=FFP). T=1
    
    T -> I : (no key sent. but a dummy login response to conclude login is
    sent).
    	 (CSG=Operational, NSG=FFP). T=1
    
    Negotiation ends at the target, with both sides settling at
    FirstBurstSize=8
    Login phase ends at the initiator. 2 login handshakes.
    
    
    Julian : What is the benefit of the above behaviour ? It results in
    inconsistent login behaviour and will only cause initiators to send
    login keys explicitly, defeating the purpose of defining defaults.
    
    I would rather the spec state that the initiator is the originator of
    the key when it uses default values, so that the login behaviour is the
    same in both scenarios above.
    
    Thanks,
    Santosh
    
    
    
    > >
    > > Julian,
    > >
    > > I've YET another login question for you :
    > >
    > > Please refer the following text in Section 2.2.4 of the Rev 08 draft
    > :
    > >
    > > "For numerical negotiations, the responding party MUST respond with
    > > the
    > > required key."
    > >
    > > When the initiator uses the default settings for a login key (i.e.
    > > does
    > > not send the key) and a target does not support that default, it has
    > > to
    > > originate the key in its login response to notify the initiator that
    > > it
    > > does not support the default.
    > >
    > > In the above example, who is the originating party & responding
    > party
    > > ?
    > > Is the initiator always considered an originating party for all the
    > > operational and security keys, even if it did not explicitly send
    > that
    > > key in its login ?
    > >
    > > If the target originated a login key, say DataPDULength, (and is
    > > therefore, to be considered as the originating party ?), based on
    > your
    > > rule quoted above, the exchange would be :
    > >
    > > I -> T : (no key is sent for DataPDULength. Assumes default of 16
    > > units.
    > > (8K).)
    > >
    > > T -> I : DataPDULength=8
    > >
    > > I -> T : DataPDULength=8  (See quoted rule above.)
    > >
    > > The definition of originating & responding party is not clear when
    > > defaults are used by the initiator and can lead to [mis-
    > > ?]interpretations  such as the above.
    > >
    > > The above response from I -> T seems redundant to me. I suggest that
    > > the
    > > draft clearly state who the originating & responding party are when
    > > defaults are used, so as to avoid confusion along the above lines.
    > >
    > > Thanks,
    > > Santosh
    
    --
    ##################################
    Santosh Rao
    Software Design Engineer,
    HP-UX iSCSI Driver Team,
    Hewlett Packard, Cupertino.
    email : santoshr@cup.hp.com
    Phone : 408-447-3751
    ##################################
    
    


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Last updated: Thu Oct 04 20:17:24 2001
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