Re: iSCSI: Connection termination conditions

["Mallikarjun C." <cbm@rose.hp.com>]

Nandakumar,

There appears to be some confusion about what is implied by graceful 
connection termination.  Transport protocol (TCP for now) defines what 
a graceful transport connection shutdown is. In section 2.2.5,  iSCSI is 
only attempting to spell out *when* it should be used, so that the iSCSI 
activity also comes to a stop gracefully.

>an iSCSI logout should precede sending
> TCP FINs

*If* the connection is logged in - yes.  As far as I can tell, 2.2.6 says 
it clearly.  The case in 3.13.5 you refer is when the connection is not
yet logged in!   Keep in mind that an iSCSI connection is nothing but 
a transport connection used to carry out iSCSI activity - as defined by 
section 7.  Based on the state of the "iSCSI activity", a Logout may or 
may not always be required.

The state transitions chapter could be of some help in understanding 
how transport and iSCSI activities are intertwined during the life of an
iSCSI connection.

Hope that clears it up.
--
Mallikarjun

Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions Organization
Hewlett-Packard MS 5668 
Roseville CA 95747

----- Original Message ----- 
From: "Nandakumar Ramamurthy" <nramamur@npd.hcltech.com>
To: <cbm@rose.hp.com>; <ips@ece.cmu.edu>
Sent: Tuesday, January 15, 2002 5:38 AM
Subject: Re: iSCSI: Connection termination conditions


> Hi Mallikarjun,
> 
> Agreed that there exists a distinction between a TCP connection
> and an iSCSI connection.  IMHO, an iSCSI logout should precede sending
> TCP FINs.  Section 2.2.6 must offer a clearer explanation in this regard.
> 
> As the section is entitled "iSCSI Connection Termination", there should be
> more
> focus on termination of an iSCSI connection. A separate section
> entitled "TCP Connection Termination" could probably speak about TCP related
> intricacies.
> 
> My understanding of iSCSI connection termination is :
> 
> An intentional and graceful iSCSI connection termination MUST occur
> only through the iSCSI logout process ( either implicit or explicit ).
> This is not clear from section 2.2.6.
> ( Are the 2 situations specified in my earlier mail valid? )
> 
> Section 3.13.5 states :
> "If the Status Class is not 0, the initiator and target MUST close the TCP
> connection."
> Does this constitute a graceful TCP connection termination?
> 
> What are the other interpretations for a "graceful" iSCSI connection
> termination?
> 
> Can "graceful" connection termination happen when it is not in full-feature
> phase?  How?
> Please describe the related mechanism.
> 
> Thanks,
> Nandakumar
> Member Technical Staff
> HCL Technologies, Chennai, INDIA.
> http://san.hcltech.com
> 
> 
> ----- Original Message -----
> From: "Mallikarjun C." <cbm@rose.hp.com>
> To: <ips@ece.cmu.edu>
> Sent: Monday, January 14, 2002 11:44 PM
> Subject: Re: iSCSI: Connection termination conditions
> 
> 
> > Nandakumar,
> >
> > As the preceding sentence indicates, the "graceful connection
> > shutdown" being referred to is the TCP connection termination.
> >
> > All the text is saying is that the an intentional and graceful
> > transport connection termination must also be "graceful" wrt iSCSI.
> > The first sentence in this section requires rewording for rev10,
> > and I suggest ignoring it for now.
> >
> > Thanks.
> > --
> > Mallikarjun
> >
> >
> > Mallikarjun Chadalapaka
> > Networked Storage Architecture
> > Network Storage Solutions Organization
> > MS 5668 Hewlett-Packard, Roseville.
> > cbm@rose.hp.com
> >
> >
> > Nandakumar Ramamurthy wrote:
> > >
> > > Hi All,
> > >
> > > Section 2.2.6 specifies two conditions for connection termination :
> > >
> > > "Graceful connection shutdowns MUST only occur when there are no
> > >  outstanding tasks that have allegiance to the connection and when the
> > > connection is not in full-feature phase."
> > >
> > > The above statement is ambiguous as to what a graceful connection
> > > shutdown is and the conditions in which this may occur. Can "graceful
> > > connection shutdown" be elaborated upon?
> > >
> > > My interpretation is that there could be 2 possible cases when graceful
> > > connection termination may occur. They are as follows:
> > >
> > > 1) A connection logout with no outstanding allegiant tasks is the first
> > > condition.
> > > In this case, the state of the connection is full feature.
> > >
> > > 2) The second case is when the connection is shutdown and the connection
> > > state is not in full feature phase i.e., in SecurityNegotiation or
> > > LoginOperationalNegotiation
> > > phase.
> > >
> > > Is that the correct interpretation?
> > >
> > > Thanks,
> > > Nandakumar
> > > Member Technical Staff
> > > HCL Technologies, Chennai, INDIA.
> > > http://san.hcltech.com
> >
> 
>