RE: iSCSI Change - New NOP-Out/In text

["Ayman Ghanem" <aghanem@cisco.com>]

From reading the new text, the initiator/target task tags are used to
indicate what the poll-bit used to do. If the task tag is valid, then a
response is requested, otherwise its a one-way message. The way I understand
1.1.1 is that the initiator can send a NOP-Out on its own and set the itt to
valid/reserved value depending on whether it is requesting a NOP-In or not.

-Ayman


> -----Original Message-----
> From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> Sandeep Joshi
> Sent: Thursday, August 16, 2001 10:40 AM
> To: Julian Satran
> Cc: ips@ece.cmu.edu
> Subject: Re: iSCSI Change - New NOP-Out/In text
>
>
>
> Julian,
>
> Two comments
>
> (1) Sec 1.1.1 should state that the initiator task tag is also valid
>     when the initiator sends a NOP-Out on its own.
>     The word "only" below is misleading (and perhaps misplaced)
>
>   >  The NOP-Out must have the Initiator Task Tag set to a valid value
> only
>   >  if a response in the form of NOP-In is requested.
>
> (2) does "as much as possible" imply zero is value (i.e. duplicate
> nothing?)
>   >    duplicating the data that was provided in the NOP-Out
>   >    (if any) as much as possible.
>
> -Sandeep
>
>
> Julian Satran wrote:
> >
> > Here  is the new NOP-Out/In text (2.12 & 2.13):
> >
> > 1.1  NOP-Out
> >
> >    Byte /    0       |       1       |       2       |       3       |
> >       /              |               |               |               |
> >      |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
> >      +---------------+---------------+---------------+---------------+
> >     0|X|I| 0x00      |1| Reserved (0)                                |
> >      +---------------+---------------+---------------+---------------+
> >     4| Reserved (0)  | DataSegmentLength                             |
> >      +---------------+---------------+---------------+---------------+
> >     8| LUN or Reserved (0)                                           |
> >      +                                                               +
> >    12|                                                               |
> >      +---------------+---------------+---------------+---------------+
> >    16| Initiator Task Tag or Reserved (0xffffffff)                   |
> >      +---------------+---------------+---------------+---------------+
> >    20| Target Transfer Tag or Reserved (0xffffffff)                  |
> >      +---------------+---------------+---------------+---------------+
> >    24| CmdSN                                                         |
> >      +---------------+---------------+---------------+---------------+
> >    28| ExpStatSN                                                     |
> >      +---------------+---------------+---------------+---------------+
> >    32/ Reserved (0)                                                  /
> >     +/                                                               /
> >      +---------------+---------------+---------------+---------------+
> >    48| Digests if any...                                             |
> >      +---------------+---------------+---------------+---------------+
> >      / DataSegment - Ping Data (optional)                            /
> >     +/                                                               /
> >      +---------------+---------------+---------------+---------------+
> >
> >    The NOP-Out with the Initiator Task Tag set to valid value (not the
> >    reserved 0xffffffff) acts as a "ping command".
> >
> >    This form of the NOP-Out can be used to verify that a connection is
> >    still active and all its components are operational. This command MAY
> >    use in-order delivery or immediate delivery. The NOP-Out may
> be useful
> >    in the case where an initiator has been waiting a long time for the
> >    response to some command, and the initiator suspects that
> there is some
> >    problem with the connection.  When a target receives the
> NOP-Out with a
> >    valid Initiator Task Tag, it should respond with a Nop-In Response,
> >    duplicating the data that was provided in the NOP-Out (if
> any) as much
> >    as possible.  If the initiator does not receive the NOP-In
> within some
> >    time (determined by the initiator), or if the data returned by the
> >    NOP-In is different from the data that was in the NOP-Out,
> the initiator
> >    may conclude that there is a problem with the connection.
> The initiator
> >    then closes the connection and may try to establish a new connection.
> >
> >    A NOP-Out should also be used to confirm a changed ExpStatSN
> if there is
> >    no other PDU to carry it for a long time.
> >
> >    The NOP-Out can be sent by an initiator because of a NOP-In with the
> >    Target Transfer Tag set to a valid value (not the reserved
> 0xffffffff).
> >    In this case the NOP-Out Target Transfer Tag must contain a copy of
> >    NOP-In Target Task Tag.
> >
> > 1.1.1     Initiator Task Tag
> >
> >    An initiator assigned identifier for the operation.
> >
> >    The NOP-Out must have the Initiator Task Tag set to a valid
> value only
> >    if a response in the form of NOP-In is requested.
> >    If the Initiator Task Tag does not contain a valid value, the CmdSN
> >    field contains as usual the next CmdSN but CmdSN is not
> advanced and the
> >    I bit must be set to 1.
> >
> > 1.1.2     Target Transfer Tag
> >
> >    A target assigned identifier for the operation.
> >
> >    The NOP-Out MUST have the Target Transfer Tag set only if it
> is issued
> >    in response to a NOP-In with a valid Target Transfer Tag, in
> which case
> >    it copies the Target Transfer Tag from the NOP-In PDU.
> >
> >    When the Target Transfer Tag is set, the LUN field MUST be
> also copied
> >    from the NOP-In.
> >
> > 1.1.3     Ping Data
> >
> >    Ping data is reflected in the NOP-In Response. Note that the
> length of
> >    the reflected data is limited to 4096 bytes and the initiator should
> >    avoid sending more than 4096 bytes. The length of ping data
> is indicated
> >    by the Data Segment Length.  0 is a valid value for the Data Segment
> >    Length - and indicates the absence of ping data.
> >
> > 1.2  NOP-In
> >
> >    Byte /    0       |       1       |       2       |       3       |
> >       /              |               |               |               |
> >      |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
> >      +---------------+---------------+---------------+---------------+
> >     0|1|1| 0x20      |1| Reserved (0)                                |
> >      +---------------+---------------+---------------+---------------+
> >     4| Reserved (0)  | DataSegmentLength                             |
> >      +---------------+---------------+---------------+---------------+
> >     8| LUN or Reserved (0)                                           |
> >      +                                                               +
> >    12|                                                               |
> >      +---------------+---------------+---------------+---------------+
> >    16| Initiator Task Tag or Reserved (0xffffffff)                   |
> >      +---------------+---------------+---------------+---------------+
> >    20| Target Transfer Tag or Reserved (0xffffffff)                  |
> >      +---------------+---------------+---------------+---------------+
> >    24| StatSN                                                        |
> >      +---------------+---------------+---------------+---------------+
> >    28| ExpCmdSN                                                      |
> >      +---------------+---------------+---------------+---------------+
> >    32| MaxCmdSN                                                      |
> >      +---------------+---------------+---------------+---------------+
> >    36/ Reserved (0)                                                  /
> >     +/                                                               /
> >      +---------------+---------------+---------------+---------------+
> >    48| Digests if any...                                             |
> >      +---------------+---------------+---------------+---------------+
> >      / DataSegment - Return Ping Data                                /
> >     +/                                                               /
> >      +---------------+---------------+---------------+---------------+
> >
> >    When a target receives the NOP-Out with a valid Initiator
> Task Tag (not
> >    the reserved value 0xffffffff), it MUST respond with a
> NOP-In with the
> >    same Initiator Task Tag that was provided in the NOP-Out Command. It
> >    SHOULD also duplicate up to first 4096 bytes of the
> initiator provided
> >    Ping Data. For such a response, the Target Transfer Tag MUST be
> >    0xffffffff.
> >
> > 1.2.1     Target Transfer Tag
> >
> >    A target assigned identifier for the operation.
> >
> >    A target may issue a NOP-In on its own to test the connection and the
> >    state of the initiator. If the target wants to test the initiator, it
> >    sets the Target Task Tag to a valid value (not the reserved
> 0xffffffff)
> >    in order to ask for an answer from the initiator. In this case the
> >    Initiator Task Tag MUST be 0xffffffff and the LUN field MUST
> contain a
> >    valid LUN. If the target wants only to test the connection, both tags
> >    MUST hold the reserved value 0xffffffff and the LUN field is
> reserved.
> >
> >    A target may also issue a NOP-In on its own to carry a
> changed ExpCmdSN
> >    and/or MaxCmdSN if there is no other PDU to carry them for a
> long time.
> >
> >    Whenever the NOP-In is not issued in response to a NOP-Out the StatSN
> >    field will contain as usual the next StatSN but StatSN for this
> >    connection is not advanced.
> >
> > 1.2.2     LUN
> >
> >    A LUN MUST be set to a correct value when the Target Transfer Tag is
> >    valid (not the reserved value 0xffffffff).
>