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RFC 7143

 
 
 

Internet Small Computer System Interface (iSCSI) Protocol (Consolidated)

Part 7 of 10, p. 170 to 198
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11.5.  Task Management Function Request

   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|.|I| 0x02      |1| Function    | Reserved                      |
     +---------------+---------------+---------------+---------------+
    4|TotalAHSLength | DataSegmentLength                             |
     +---------------+---------------+---------------+---------------+
    8| Logical Unit Number (LUN) or Reserved                         |
     +                                                               +
   12|                                                               |
     +---------------+---------------+---------------+---------------+
   16| Initiator Task Tag                                            |
     +---------------+---------------+---------------+---------------+
   20| Referenced Task Tag or 0xffffffff                             |
     +---------------+---------------+---------------+---------------+
   24| CmdSN                                                         |
     +---------------+---------------+---------------+---------------+
   28| ExpStatSN                                                     |
     +---------------+---------------+---------------+---------------+
   32| RefCmdSN or Reserved                                          |
     +---------------+---------------+---------------+---------------+
   36| ExpDataSN or Reserved                                         |
     +---------------+---------------+---------------+---------------+
   40/ Reserved                                                      /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
   48| Header-Digest (optional)                                      |
     +---------------+---------------+---------------+---------------+

11.5.1.  Function

   The task management functions provide an initiator with a way to
   explicitly control the execution of one or more tasks (SCSI and iSCSI
   tasks).  The task management function codes are listed below.  For a
   more detailed description of SCSI task management, see [SAM2].

      1  ABORT TASK - aborts the task identified by the Referenced Task
         Tag field.

      2  ABORT TASK SET - aborts all tasks issued via this session on
         the LU.

      3  CLEAR ACA - clears the Auto Contingent Allegiance condition.

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      4  CLEAR TASK SET - aborts all tasks in the appropriate task set
         as defined by the TST field in the Control mode page
         (see [SPC3]).

      5  LOGICAL UNIT RESET

      6  TARGET WARM RESET

      7  TARGET COLD RESET

      8  TASK REASSIGN - reassigns connection allegiance for the task
         identified by the Initiator Task Tag field to this connection,
         thus resuming the iSCSI exchanges for the task.

   Values 9-12 are assigned in [RFC7144].  All other possible values for
   the Function field are unassigned.

   For all these functions, the Task Management Function Response MUST
   be returned as detailed in Section 11.6.  All these functions apply
   to the referenced tasks, regardless of whether they are proper SCSI
   tasks or tagged iSCSI operations.  Task management requests must act
   on all the commands from the same session having a CmdSN lower than
   the task management CmdSN.  LOGICAL UNIT RESET, TARGET WARM RESET,
   and TARGET COLD RESET may affect commands from other sessions or
   commands from the same session, regardless of their CmdSN value.

   If the task management request is marked for immediate delivery, it
   must be considered immediately for execution, but the operations
   involved (all or part of them) may be postponed to allow the target
   to receive all relevant tasks.  According to [SAM2], for all the
   tasks covered by the task management response (i.e., with a CmdSN
   lower than the task management command CmdSN), except for the task
   management response to a TASK REASSIGN, additional responses MUST NOT
   be delivered to the SCSI layer after the task management response.
   The iSCSI initiator MAY deliver to the SCSI layer all responses
   received before the task management response (i.e., it is a matter of
   implementation if the SCSI responses that are received before the
   task management response but after the task management request was
   issued are delivered to the SCSI layer by the iSCSI layer in the
   initiator).  The iSCSI target MUST ensure that no responses for the
   tasks covered by a task management function are delivered to the
   iSCSI initiator after the task management response, except for a task
   covered by a TASK REASSIGN.

   For ABORT TASK SET and CLEAR TASK SET, the issuing initiator MUST
   continue to respond to all valid Target Transfer Tags (received via
   R2T, Text Response, NOP-In, or SCSI Data-In PDUs) related to the
   affected task set, even after issuing the task management request.

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   The issuing initiator SHOULD, however, terminate (i.e., by setting
   the F bit to 1) these response sequences as quickly as possible.  The
   target for its part MUST wait for responses on all affected Target
   Transfer Tags before acting on either of these two task management
   requests.  If all or part of the response sequence is not received
   (due to digest errors) for a valid TTT, the target MAY treat it as a
   case of a within-command error recovery class (see Section 7.1.4.1)
   if it is supporting ErrorRecoveryLevel >= 1 or, alternatively, may
   drop the connection to complete the requested task set function.

   If an ABORT TASK is issued for a task created by an immediate
   command, then the RefCmdSN MUST be that of the task management
   request itself (i.e., the CmdSN and RefCmdSN are equal); otherwise,
   the RefCmdSN MUST be set to the CmdSN of the task to be aborted
   (lower than the CmdSN).

   If the connection is still active (i.e., it is not undergoing an
   implicit or explicit logout), an ABORT TASK MUST be issued on the
   same connection to which the task to be aborted is allegiant at the
   time the task management request is issued.  If the connection is
   implicitly or explicitly logged out (i.e., no other request will be
   issued on the failing connection and no other response will be
   received on the failing connection), then an ABORT TASK function
   request may be issued on another connection.  This task management
   request will then establish a new allegiance for the command to be
   aborted as well as abort it (i.e., the task to be aborted will not
   have to be retried or reassigned, and its status, if sent but not
   acknowledged, will be resent followed by the task management
   response).

   At the target, an ABORT TASK function MUST NOT be executed on a task
   management request; such a request MUST result in a task management
   response of "Function rejected".

   For the LOGICAL UNIT RESET function, the target MUST behave as
   dictated by the Logical Unit Reset function in [SAM2].

   The implementation of the TARGET WARM RESET function and the TARGET
   COLD RESET function is OPTIONAL and, when implemented, should act as
   described below.  The TARGET WARM RESET is also subject to SCSI
   access controls on the requesting initiator as defined in [SPC3].
   When authorization fails at the target, the appropriate response as
   described in Section 11.6.1 MUST be returned by the target.  The
   TARGET COLD RESET function is not subject to SCSI access controls,
   but its execution privileges may be managed by iSCSI mechanisms such
   as login authentication.

Top      Up      ToC       Page 173 
   When executing the TARGET WARM RESET and TARGET COLD RESET functions,
   the target cancels all pending operations on all LUs known by the
   issuing initiator.  Both functions are equivalent to the TARGET RESET
   function specified by [SAM2].  They can affect many other initiators
   logged in with the servicing SCSI target port.

   Additionally, the target MUST treat the TARGET COLD RESET function as
   a power-on event, thus terminating all of its TCP connections to all
   initiators (all sessions are terminated).  For this reason, the
   service response (defined by [SAM2]) for this SCSI task management
   function may not be reliably delivered to the issuing initiator port.

   For the TASK REASSIGN function, the target should reassign the
   connection allegiance to this new connection (and thus resume iSCSI
   exchanges for the task).  TASK REASSIGN MUST ONLY be received by the
   target after the connection on which the command was previously
   executing has been successfully logged out.  The task management
   response MUST be issued before the reassignment becomes effective.

   For additional usage semantics, see Section 7.2.

   At the target, a TASK REASSIGN function request MUST NOT be executed
   to reassign the connection allegiance of a Task Management Function
   Request, an active text negotiation task, or a Logout task; such a
   request MUST result in a task management response of "Function
   rejected".

   TASK REASSIGN MUST be issued as an immediate command.

11.5.2.  TotalAHSLength and DataSegmentLength

   For this PDU, TotalAHSLength and DataSegmentLength MUST be 0.

11.5.3.  LUN

   This field is required for functions that address a specific LU
   (ABORT TASK, CLEAR TASK SET, ABORT TASK SET, CLEAR ACA, LOGICAL UNIT
   RESET) and is reserved in all others.

11.5.4.  Referenced Task Tag

   This is the Initiator Task Tag of the task to be aborted for the
   ABORT TASK function or reassigned for the TASK REASSIGN function.
   For all the other functions, this field MUST be set to the reserved
   value 0xffffffff.

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11.5.5.  RefCmdSN

   If an ABORT TASK is issued for a task created by an immediate
   command, then the RefCmdSN MUST be that of the task management
   request itself (i.e., the CmdSN and RefCmdSN are equal).

   For an ABORT TASK of a task created by a non-immediate command, the
   RefCmdSN MUST be set to the CmdSN of the task identified by the
   Referenced Task Tag field.  Targets must use this field as described
   in Section 11.6.1 when the task identified by the Referenced Task Tag
   field is not with the target.

   Otherwise, this field is reserved.

11.5.6.  ExpDataSN

   For recovery purposes, the iSCSI target and initiator maintain a data
   acknowledgment reference number -- the first input DataSN number
   unacknowledged by the initiator.  When issuing a new command, this
   number is set to 0.  If the function is TASK REASSIGN, which
   establishes a new connection allegiance for a previously issued read
   or bidirectional command, the ExpDataSN will contain an updated data
   acknowledgment reference number or the value 0; the latter indicates
   that the data acknowledgment reference number is unchanged.  The
   initiator MUST discard any data PDUs from the previous execution that
   it did not acknowledge, and the target MUST transmit all Data-In PDUs
   (if any) starting with the data acknowledgment reference number.  The
   number of retransmitted PDUs may or may not be the same as the
   original transmission, depending on if there was a change in
   MaxRecvDataSegmentLength in the reassignment.  The target MAY also
   send no more Data-In PDUs if all data has been acknowledged.

   The value of ExpDataSN MUST be 0 or higher than the DataSN of the
   last acknowledged Data-In PDU, but not larger than DataSN + 1 of the
   last Data-IN PDU sent by the target.  Any other value MUST be ignored
   by the target.

   For other functions, this field is reserved.

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11.6.  Task Management Function Response

   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|.|.| 0x22      |1| Reserved    | Response      | Reserved      |
     +---------------+---------------+---------------+---------------+
    4|TotalAHSLength | DataSegmentLength                             |
     +---------------------------------------------------------------+
    8/ Reserved                                                      /
     /                                                               /
     +---------------+---------------+---------------+---------------+
   16| Initiator Task Tag                                            |
     +---------------+---------------+---------------+---------------+
   20| Reserved                                                      |
     +---------------+---------------+---------------+---------------+
   24| StatSN                                                        |
     +---------------+---------------+---------------+---------------+
   28| ExpCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   32| MaxCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   36/ Reserved                                                      /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
   48| Header-Digest (optional)                                      |
     +---------------+---------------+---------------+---------------+

   For the functions ABORT TASK, ABORT TASK SET, CLEAR ACA, CLEAR TASK
   SET, LOGICAL UNIT RESET, TARGET COLD RESET, TARGET WARM RESET, and
   TASK REASSIGN, the target performs the requested task management
   function and sends a task management response back to the initiator.
   For TASK REASSIGN, the new connection allegiance MUST ONLY become
   effective at the target after the target issues the task management
   response.

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11.6.1.  Response

   The target provides a response, which may take on the following
   values:

       0 - Function complete
       1 - Task does not exist
       2 - LUN does not exist
       3 - Task still allegiant
       4 - Task allegiance reassignment not supported
       5 - Task management function not supported
       6 - Function authorization failed
     255 - Function rejected

   In addition to the above values, the value 7 is defined by [RFC7144].

   For a discussion on the usage of response codes 3 and 4, see
   Section 7.2.2.

   For the TARGET COLD RESET and TARGET WARM RESET functions, the target
   cancels all pending operations across all LUs known to the issuing
   initiator.  For the TARGET COLD RESET function, the target MUST then
   close all of its TCP connections to all initiators (terminates all
   sessions).

   The mapping of the response code into a SCSI service response code
   value, if needed, is outside the scope of this document.  However, in
   symbolic terms, Response values 0 and 1 map to the SCSI service
   response of FUNCTION COMPLETE.  Response value 2 maps to the SCSI
   service response of INCORRECT LOGICAL UNIT NUMBER.  All other
   Response values map to the SCSI service response of FUNCTION
   REJECTED.  If a Task Management Function Response PDU does not arrive
   before the session is terminated, the SCSI service response is
   SERVICE DELIVERY OR TARGET FAILURE.

   The response to ABORT TASK SET and CLEAR TASK SET MUST only be issued
   by the target after all of the commands affected have been received
   by the target, the corresponding task management functions have been
   executed by the SCSI target, and the delivery of all responses
   delivered until the task management function completion has been
   confirmed (acknowledged through the ExpStatSN) by the initiator on
   all connections of this session.  For the exact timeline of events,
   refer to Sections 4.2.3.3 and 4.2.3.4.

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   For the ABORT TASK function,

      a) if the Referenced Task Tag identifies a valid task leading to a
         successful termination, then targets must return the "Function
         complete" response.

      b) if the Referenced Task Tag does not identify an existing task
         but the CmdSN indicated by the RefCmdSN field in the Task
         Management Function Request is within the valid CmdSN window
         and less than the CmdSN of the Task Management Function Request
         itself, then targets must consider the CmdSN as received and
         return the "Function complete" response.

      c) if the Referenced Task Tag does not identify an existing task
         and the CmdSN indicated by the RefCmdSN field in the Task
         Management Function Request is outside the valid CmdSN window,
         then targets must return the "Task does not exist" response.

   For response semantics on function types that can potentially impact
   multiple active tasks on the target, see Section 4.2.3.

11.6.2.  TotalAHSLength and DataSegmentLength

   For this PDU, TotalAHSLength and DataSegmentLength MUST be 0.

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11.7.  SCSI Data-Out and SCSI Data-In

   The SCSI Data-Out PDU for write operations has the following format:

   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|.|.| 0x05      |F| Reserved                                    |
     +---------------+---------------+---------------+---------------+
    4|TotalAHSLength | DataSegmentLength                             |
     +---------------+---------------+---------------+---------------+
    8| LUN or Reserved                                               |
     +                                                               +
   12|                                                               |
     +---------------+---------------+---------------+---------------+
   16| Initiator Task Tag                                            |
     +---------------+---------------+---------------+---------------+
   20| Target Transfer Tag or 0xffffffff                             |
     +---------------+---------------+---------------+---------------+
   24| Reserved                                                      |
     +---------------+---------------+---------------+---------------+
   28| ExpStatSN                                                     |
     +---------------+---------------+---------------+---------------+
   32| Reserved                                                      |
     +---------------+---------------+---------------+---------------+
   36| DataSN                                                        |
     +---------------+---------------+---------------+---------------+
   40| Buffer Offset                                                 |
     +---------------+---------------+---------------+---------------+
   44| Reserved                                                      |
     +---------------+---------------+---------------+---------------+
   48| Header-Digest (optional)                                      |
     +---------------+---------------+---------------+---------------+
     / DataSegment                                                   /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
     | Data-Digest (optional)                                        |
     +---------------+---------------+---------------+---------------+

Top      Up      ToC       Page 179 
   The SCSI Data-In PDU for read operations has the following format:

   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|.|.| 0x25      |F|A|0 0 0|O|U|S| Reserved      |Status or Rsvd |
     +---------------+---------------+---------------+---------------+
    4|TotalAHSLength | DataSegmentLength                             |
     +---------------+---------------+---------------+---------------+
    8| LUN or Reserved                                               |
     +                                                               +
   12|                                                               |
     +---------------+---------------+---------------+---------------+
   16| Initiator Task Tag                                            |
     +---------------+---------------+---------------+---------------+
   20| Target Transfer Tag or 0xffffffff                             |
     +---------------+---------------+---------------+---------------+
   24| StatSN or Reserved                                            |
     +---------------+---------------+---------------+---------------+
   28| ExpCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   32| MaxCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   36| DataSN                                                        |
     +---------------+---------------+---------------+---------------+
   40| Buffer Offset                                                 |
     +---------------+---------------+---------------+---------------+
   44| Residual Count                                                |
     +---------------+---------------+---------------+---------------+
   48| Header-Digest (optional)                                      |
     +---------------+---------------+---------------+---------------+
     / DataSegment                                                   /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
     | Data-Digest (optional)                                        |
     +---------------+---------------+---------------+---------------+

   Status can accompany the last Data-In PDU if the command did not end
   with an exception (i.e., the status is "good status" -- GOOD,
   CONDITION MET, or INTERMEDIATE-CONDITION MET).  The presence of
   status (and of a residual count) is signaled via the S flag bit.
   Although targets MAY choose to send even non-exception status in
   separate responses, initiators MUST support non-exception status in
   Data-In PDUs.

Top      Up      ToC       Page 180 
11.7.1.  F (Final) Bit

   For outgoing data, this bit is 1 for the last PDU of unsolicited data
   or the last PDU of a sequence that answers an R2T.

   For incoming data, this bit is 1 for the last input (read) data PDU
   of a sequence.  Input can be split into several sequences, each
   having its own F bit.  Splitting the data stream into sequences does
   not affect DataSN counting on Data-In PDUs.  It MAY be used as a
   "change direction" indication for bidirectional operations that need
   such a change.

   DataSegmentLength MUST NOT exceed MaxRecvDataSegmentLength for the
   direction it is sent, and the total of all the DataSegmentLength of
   all PDUs in a sequence MUST NOT exceed MaxBurstLength (or
   FirstBurstLength for unsolicited data).  However, the number of
   individual PDUs in a sequence (or in total) may be higher than the
   ratio of MaxBurstLength (or FirstBurstLength) to
   MaxRecvDataSegmentLength (as PDUs may be limited in length by the
   capabilities of the sender).  Using a DataSegmentLength of 0 may
   increase beyond what is reasonable for the number of PDUs and should
   therefore be avoided.

   For bidirectional operations, the F bit is 1 for both the end of the
   input sequences and the end of the output sequences.

11.7.2.  A (Acknowledge) Bit

   For sessions with ErrorRecoveryLevel=1 or higher, the target sets
   this bit to 1 to indicate that it requests a positive acknowledgment
   from the initiator for the data received.  The target should use the
   A bit moderately; it MAY only set the A bit to 1 once every
   MaxBurstLength bytes, or on the last Data-In PDU that concludes the
   entire requested read data transfer for the task from the target's
   perspective, and it MUST NOT do so more frequently.  The target MUST
   NOT set to 1 the A bit for sessions with ErrorRecoveryLevel=0.  The
   initiator MUST ignore the A bit set to 1 for sessions with
   ErrorRecoveryLevel=0.

   On receiving a Data-In PDU with the A bit set to 1 on a session with
   ErrorRecoveryLevel greater than 0, if there are no holes in the read
   data until that Data-In PDU, the initiator MUST issue a SNACK of type
   DataACK, except when it is able to acknowledge the status for the
   task immediately via the ExpStatSN on other outbound PDUs if the
   status for the task is also received.  In the latter case
   (acknowledgment through the ExpStatSN), sending a SNACK of type
   DataACK in response to the A bit is OPTIONAL, but if it is done, it
   must not be sent after the status acknowledgment through the

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   ExpStatSN.  If the initiator has detected holes in the read data
   prior to that Data-In PDU, it MUST postpone issuing the SNACK of type
   DataACK until the holes are filled.  An initiator also MUST NOT
   acknowledge the status for the task before those holes are filled.  A
   status acknowledgment for a task that generated the Data-In PDUs is
   considered by the target as an implicit acknowledgment of the Data-In
   PDUs if such an acknowledgment was requested by the target.

11.7.3.  Flags (Byte 1)

   The last SCSI data packet sent from a target to an initiator for a
   SCSI command that completed successfully (with a status of GOOD,
   CONDITION MET, INTERMEDIATE, or INTERMEDIATE-CONDITION MET) may also
   optionally contain the Status for the data transfer.  In this case,
   Sense Data cannot be sent together with the Command Status.  If the
   command is completed with an error, then the response and sense data
   MUST be sent in a SCSI Response PDU (i.e., MUST NOT be sent in a SCSI
   data packet).  For bidirectional commands, the status MUST be sent in
   a SCSI Response PDU.

      bit 2-4          - Reserved.

      bit 5-6          - used the same as in a SCSI Response.  These
                         bits are only valid when S is set to 1.  For
                         details, see Section 11.4.1.

      bit 7 S (status) - set to indicate that the Command Status field
                         contains status.  If this bit is set to 1, the
                         F bit MUST also be set to 1.

   The fields StatSN, Status, and Residual Count only have meaningful
   content if the S bit is set to 1.  The values for these fields are
   defined in Section 11.4.

11.7.4.  Target Transfer Tag and LUN

   On outgoing data, the Target Transfer Tag is provided to the target
   if the transfer is honoring an R2T.  In this case, the Target
   Transfer Tag field is a replica of the Target Transfer Tag provided
   with the R2T.

   On incoming data, the Target Transfer Tag and LUN MUST be provided by
   the target if the A bit is set to 1; otherwise, they are reserved.
   The Target Transfer Tag and LUN are copied by the initiator into the
   SNACK of type DataACK that it issues as a result of receiving a SCSI
   Data-In PDU with the A bit set to 1.

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   The Target Transfer Tag values are not specified by this protocol,
   except that the value 0xffffffff is reserved and means that the
   Target Transfer Tag is not supplied.  If the Target Transfer Tag is
   provided, then the LUN field MUST hold a valid value and be
   consistent with whatever was specified with the command; otherwise,
   the LUN field is reserved.

11.7.5.  DataSN

   For input (read) or bidirectional Data-In PDUs, the DataSN is the
   input PDU number within the data transfer for the command identified
   by the Initiator Task Tag.

   R2T and Data-In PDUs, in the context of bidirectional commands, share
   the numbering sequence (see Section 4.2.2.4).

   For output (write) data PDUs, the DataSN is the Data-Out PDU number
   within the current output sequence.  Either the current output
   sequence is identified by the Initiator Task Tag (for unsolicited
   data) or it is a data sequence generated for one R2T (for data
   solicited through R2T).

11.7.6.  Buffer Offset

   The Buffer Offset field contains the offset of this PDU payload data
   within the complete data transfer.  The sum of the buffer offset and
   length should not exceed the expected transfer length for the
   command.

   The order of data PDUs within a sequence is determined by
   DataPDUInOrder.  When set to Yes, it means that PDUs have to be in
   increasing buffer offset order and overlays are forbidden.

   The ordering between sequences is determined by DataSequenceInOrder.
   When set to Yes, it means that sequences have to be in increasing
   buffer offset order and overlays are forbidden.

11.7.7.  DataSegmentLength

   This is the data payload length of a SCSI Data-In or SCSI Data-Out
   PDU.  The sending of 0-length data segments should be avoided, but
   initiators and targets MUST be able to properly receive 0-length data
   segments.

   The data segments of Data-In and Data-Out PDUs SHOULD be filled to
   the integer number of 4-byte words (real payload), unless the F bit
   is set to 1.

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11.8.  Ready To Transfer (R2T)

   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|.|.| 0x31      |1| Reserved                                    |
     +---------------+---------------+---------------+---------------+
    4|TotalAHSLength | DataSegmentLength                             |
     +---------------+---------------+---------------+---------------+
    8| LUN                                                           |
     +                                                               +
   12|                                                               |
     +---------------+---------------+---------------+---------------+
   16| Initiator Task Tag                                            |
     +---------------+---------------+---------------+---------------+
   20| Target Transfer Tag                                           |
     +---------------+---------------+---------------+---------------+
   24| StatSN                                                        |
     +---------------+---------------+---------------+---------------+
   28| ExpCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   32| MaxCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   36| R2TSN                                                         |
     +---------------+---------------+---------------+---------------+
   40| Buffer Offset                                                 |
     +---------------+---------------+---------------+---------------+
   44| Desired Data Transfer Length                                  |
     +---------------------------------------------------------------+
   48| Header-Digest (optional)                                      |
     +---------------+---------------+---------------+---------------+

   When an initiator has submitted a SCSI command with data that passes
   from the initiator to the target (write), the target may specify
   which blocks of data it is ready to receive.  The target may request
   that the data blocks be delivered in whichever order is convenient
   for the target at that particular instant.  This information is
   passed from the target to the initiator in the Ready To Transfer
   (R2T) PDU.

   In order to allow write operations without an explicit initial R2T,
   the initiator and target MUST have negotiated the key InitialR2T to
   No during login.

   An R2T MAY be answered with one or more SCSI Data-Out PDUs with a
   matching Target Transfer Tag.  If an R2T is answered with a single
   Data-Out PDU, the buffer offset in the data PDU MUST be the same as

Top      Up      ToC       Page 184 
   the one specified by the R2T, and the data length of the data PDU
   MUST be the same as the Desired Data Transfer Length specified in the
   R2T.  If the R2T is answered with a sequence of data PDUs, the buffer
   offset and length MUST be within the range of those specified by the
   R2T, and the last PDU MUST have the F bit set to 1.  If the last PDU
   (marked with the F bit) is received before the Desired Data Transfer
   Length is transferred, a target MAY choose to reject that PDU with
   the "Protocol Error" reason code.  DataPDUInOrder governs the
   Data-Out PDU ordering.  If DataPDUInOrder is set to Yes, the buffer
   offsets and lengths for consecutive PDUs MUST form a continuous
   non-overlapping range, and the PDUs MUST be sent in increasing offset
   order.

   The target may send several R2T PDUs.  It therefore can have a number
   of pending data transfers.  The number of outstanding R2T PDUs is
   limited by the value of the negotiated key MaxOutstandingR2T.  Within
   a task, outstanding R2Ts MUST be fulfilled by the initiator in the
   order in which they were received.

   R2T PDUs MAY also be used to recover Data-Out PDUs.  Such an R2T
   (Recovery-R2T) is generated by a target upon detecting the loss of
   one or more Data-Out PDUs due to:

      - Digest error

      - Sequence error

      - Sequence reception timeout

   A Recovery-R2T carries the next unused R2TSN but requests part of or
   the entire data burst that an earlier R2T (with a lower R2TSN) had
   already requested.

   DataSequenceInOrder governs the buffer offset ordering in consecutive
   R2Ts.  If DataSequenceInOrder is Yes, then consecutive R2Ts MUST
   refer to continuous non-overlapping ranges, except for Recovery-R2Ts.

11.8.1.  TotalAHSLength and DataSegmentLength

   For this PDU, TotalAHSLength and DataSegmentLength MUST be 0.

11.8.2.  R2TSN

   R2TSN is the R2T PDU input PDU number within the command identified
   by the Initiator Task Tag.

   For bidirectional commands, R2T and Data-In PDUs share the input PDU
   numbering sequence (see Section 4.2.2.4).

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11.8.3.  StatSN

   The StatSN field will contain the next StatSN.  The StatSN for this
   connection is not advanced after this PDU is sent.

11.8.4.  Desired Data Transfer Length and Buffer Offset

   The target specifies how many bytes it wants the initiator to send
   because of this R2T PDU.  The target may request the data from the
   initiator in several chunks, not necessarily in the original order of
   the data.  The target therefore also specifies a buffer offset that
   indicates the point at which the data transfer should begin, relative
   to the beginning of the total data transfer.  The Desired Data
   Transfer Length MUST NOT be 0 and MUST NOT exceed MaxBurstLength.

11.8.5.  Target Transfer Tag

   The target assigns its own tag to each R2T request that it sends to
   the initiator.  This tag can be used by the target to easily identify
   the data it receives.  The Target Transfer Tag and LUN are copied in
   the outgoing data PDUs and are only used by the target.  There is no
   protocol rule about the Target Transfer Tag except that the value
   0xffffffff is reserved and MUST NOT be sent by a target in an R2T.

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11.9.  Asynchronous Message

   An Asynchronous Message may be sent from the target to the initiator
   without corresponding to a particular command.  The target specifies
   the reason for the event and sense data.

   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|.|.| 0x32      |1| Reserved                                    |
     +---------------+---------------+---------------+---------------+
    4|TotalAHSLength | DataSegmentLength                             |
     +---------------+---------------+---------------+---------------+
    8| LUN or Reserved                                               |
     +                                                               +
   12|                                                               |
     +---------------+---------------+---------------+---------------+
   16| 0xffffffff                                                    |
     +---------------+---------------+---------------+---------------+
   20| Reserved                                                      |
     +---------------+---------------+---------------+---------------+
   24| StatSN                                                        |
     +---------------+---------------+---------------+---------------+
   28| ExpCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   32| MaxCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   36| AsyncEvent    | AsyncVCode    | Parameter1 or Reserved        |
     +---------------+---------------+---------------+---------------+
   40| Parameter2 or Reserved        | Parameter3 or Reserved        |
     +---------------+---------------+---------------+---------------+
   44| Reserved                                                      |
     +---------------+---------------+---------------+---------------+
   48| Header-Digest (optional)                                      |
     +---------------+---------------+---------------+---------------+
     / DataSegment - Sense Data and iSCSI Event Data                 /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
     | Data-Digest (optional)                                        |
     +---------------+---------------+---------------+---------------+

   Some Asynchronous Messages are strictly related to iSCSI, while
   others are related to SCSI [SAM2].

   The StatSN counts this PDU as an acknowledgeable event (the StatSN is
   advanced), which allows for initiator and target state
   synchronization.

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11.9.1.  AsyncEvent

   The codes used for iSCSI Asynchronous Messages (events) are:

        0 (SCSI Async Event) - a SCSI asynchronous event is reported in
          the sense data.  Sense Data that accompanies the report, in
          the data segment, identifies the condition.  The sending of a
          SCSI event ("asynchronous event reporting" in SCSI
          terminology) is dependent on the target support for SCSI
          asynchronous event reporting (see [SAM2]) as indicated in the
          standard INQUIRY data (see [SPC3]).  Its use may be enabled by
          parameters in the SCSI Control mode page (see [SPC3]).

        1 (Logout Request) - the target requests Logout.  This Async
          Message MUST be sent on the same connection as the one
          requesting to be logged out.  The initiator MUST honor this
          request by issuing a Logout as early as possible but no later
          than Parameter3 seconds.  The initiator MUST send a Logout
          with a reason code of "close the connection" OR "close the
          session" to close all the connections.  Once this message is
          received, the initiator SHOULD NOT issue new iSCSI commands on
          the connection to be logged out.  The target MAY reject any
          new I/O requests that it receives after this message with the
          reason code "Waiting for Logout".  If the initiator does not
          log out in Parameter3 seconds, the target should send an Async
          PDU with iSCSI event code "Dropped the connection" if possible
          or simply terminate the transport connection.  Parameter1 and
          Parameter2 are reserved.

        2 (Connection Drop Notification) - the target indicates that it
          will drop the connection.

          The Parameter1 field indicates the CID of the connection that
          is going to be dropped.

          The Parameter2 field (Time2Wait) indicates, in seconds, the
          minimum time to wait before attempting to reconnect or
          reassign.

          The Parameter3 field (Time2Retain) indicates the maximum time
          allowed to reassign commands after the initial wait (in
          Parameter2).

          If the initiator does not attempt to reconnect and/or reassign
          the outstanding commands within the time specified by
          Parameter3, or if Parameter3 is 0, the target will terminate

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          all outstanding commands on this connection.  In this case, no
          other responses should be expected from the target for the
          outstanding commands on this connection.

          A value of 0 for Parameter2 indicates that reconnect can be
          attempted immediately.

        3 (Session Drop Notification) - the target indicates that it
          will drop all the connections of this session.

          The Parameter1 field is reserved.

          The Parameter2 field (Time2Wait) indicates, in seconds, the
          minimum time to wait before attempting to reconnect.

          The Parameter3 field (Time2Retain) indicates the maximum time
          allowed to reassign commands after the initial wait (in
          Parameter2).

          If the initiator does not attempt to reconnect and/or reassign
          the outstanding commands within the time specified by
          Parameter3, or if Parameter3 is 0, the session is terminated.
          In this case, the target will terminate all outstanding
          commands in this session; no other responses should be
          expected from the target for the outstanding commands in this
          session.  A value of 0 for Parameter2 indicates that reconnect
          can be attempted immediately.

        4 (Negotiation Request) - the target requests parameter
          negotiation on this connection.  The initiator MUST honor this
          request by issuing a Text Request (that can be empty) on the
          same connection as early as possible, but no later than
          Parameter3 seconds, unless a Text Request is already pending
          on the connection, or by issuing a Logout Request.  If the
          initiator does not issue a Text Request, the target may
          reissue the Asynchronous Message requesting parameter
          negotiation.

Top      Up      ToC       Page 189 
        5 (Task Termination) - all active tasks for a LU with a matching
          LUN field in the Async Message PDU are being terminated.  The
          receiving initiator iSCSI layer MUST respond to this message
          by taking the following steps, in order:

          - Stop Data-Out transfers on that connection for all active
            TTTs for the affected LUN quoted in the Async Message PDU.

          - Acknowledge the StatSN of the Async Message PDU via a
            NOP-Out PDU with ITT=0xffffffff (i.e., non-ping flavor),
            while copying the LUN field from the Async Message to
            NOP-Out.

          This value of AsyncEvent, however, MUST NOT be used on an
          iSCSI session unless the new TaskReporting text key defined in
          Section 13.23 was negotiated to FastAbort on the session.

    248-255 (Vendor-unique) - vendor-specific iSCSI event.  The
          AsyncVCode details the vendor code, and data MAY accompany the
          report.

   All other event codes are unassigned.

11.9.2.  AsyncVCode

   AsyncVCode is a vendor-specific detail code that is only valid if the
   AsyncEvent field indicates a vendor-specific event.  Otherwise, it is
   reserved.

11.9.3.  LUN

   The LUN field MUST be valid if AsyncEvent is 0.  Otherwise, this
   field is reserved.

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11.9.4.  Sense Data and iSCSI Event Data

   For a SCSI event, this data accompanies the report in the data
   segment and identifies the condition.

   For an iSCSI event, additional vendor-unique data MAY accompany the
   Async event.  Initiators MAY ignore the data when not understood,
   while processing the rest of the PDU.

   If the DataSegmentLength is not 0, the format of the DataSegment is
   as follows:

   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|SenseLength                    | Sense Data                    |
     +---------------+---------------+---------------+---------------+
    x/ Sense Data                                                    /
     +---------------+---------------+---------------+---------------+
    y/ iSCSI Event Data                                              /
     /                                                               /
     +---------------+---------------+---------------+---------------+
    z|

11.9.4.1.  SenseLength

   This is the length of Sense Data.  When the Sense Data field is empty
   (e.g., the event is not a SCSI event), SenseLength is 0.

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11.10.  Text Request

   The Text Request is provided to allow for the exchange of information
   and for future extensions.  It permits the initiator to inform a
   target of its capabilities or request some special operations.

   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|.|I| 0x04      |F|C| Reserved                                  |
     +---------------+---------------+---------------+---------------+
    4|TotalAHSLength | DataSegmentLength                             |
     +---------------+---------------+---------------+---------------+
    8| LUN or Reserved                                               |
     +                                                               +
   12|                                                               |
     +---------------+---------------+---------------+---------------+
   16| Initiator Task Tag                                            |
     +---------------+---------------+---------------+---------------+
   20| Target Transfer Tag or 0xffffffff                             |
     +---------------+---------------+---------------+---------------+
   24| CmdSN                                                         |
     +---------------+---------------+---------------+---------------+
   28| ExpStatSN                                                     |
     +---------------+---------------+---------------+---------------+
   32/ Reserved                                                      /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
   48| Header-Digest (optional)                                      |
     +---------------+---------------+---------------+---------------+
     / DataSegment (Text)                                            /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
     | Data-Digest (optional)                                        |
     +---------------+---------------+---------------+---------------+

   An initiator MUST NOT have more than one outstanding Text Request on
   a connection at any given time.

   On a connection failure, an initiator must either explicitly abort
   any active allegiant text negotiation task or cause such a task to be
   implicitly terminated by the target.

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11.10.1.  F (Final) Bit

   When set to 1, this bit indicates that this is the last or only Text
   Request in a sequence of Text Requests; otherwise, it indicates that
   more Text Requests will follow.

11.10.2.  C (Continue) Bit

   When set to 1, this bit indicates that the text (set of key=value
   pairs) in this Text Request is not complete (it will be continued on
   subsequent Text Requests); otherwise, it indicates that this Text
   Request ends a set of key=value pairs.  A Text Request with the C bit
   set to 1 MUST have the F bit set to 0.

11.10.3.  Initiator Task Tag

   This is the initiator-assigned identifier for this Text Request.  If
   the command is sent as part of a sequence of Text Requests and
   responses, the Initiator Task Tag MUST be the same for all the
   requests within the sequence (similar to linked SCSI commands).  The
   I bit for all requests in a sequence also MUST be the same.

11.10.4.  Target Transfer Tag

   When the Target Transfer Tag is set to the reserved value 0xffffffff,
   it tells the target that this is a new request, and the target resets
   any internal state associated with the Initiator Task Tag (resets the
   current negotiation state).

   The target sets the Target Transfer Tag in a Text Response to a value
   other than the reserved value 0xffffffff whenever it indicates that
   it has more data to send or more operations to perform that are
   associated with the specified Initiator Task Tag.  It MUST do so
   whenever it sets the F bit to 0 in the response.  By copying the
   Target Transfer Tag from the response to the next Text Request, the
   initiator tells the target to continue the operation for the specific
   Initiator Task Tag.  The initiator MUST ignore the Target Transfer
   Tag in the Text Response when the F bit is set to 1.

   This mechanism allows the initiator and target to transfer a large
   amount of textual data over a sequence of text-command/text-response
   exchanges or to perform extended negotiation sequences.

   If the Target Transfer Tag is not 0xffffffff, the LUN field MUST be
   sent by the target in the Text Response.

Top      Up      ToC       Page 193 
   A target MAY reset its internal negotiation state if an exchange is
   stalled by the initiator for a long time or if it is running out of
   resources.

   Long Text Responses are handled as shown in the following example:

      I->T Text SendTargets=All (F = 1, TTT = 0xffffffff)

      T->I Text <part 1> (F = 0, TTT = 0x12345678)

      I->T Text <empty> (F = 1, TTT = 0x12345678)

      T->I Text <part 2> (F = 0, TTT = 0x12345678)

      I->T Text <empty> (F = 1, TTT = 0x12345678)

      ...

      T->I Text <part n> (F = 1, TTT = 0xffffffff)

11.10.5.  Text

   The data lengths of a Text Request MUST NOT exceed the iSCSI target
   MaxRecvDataSegmentLength (a parameter that is negotiated per
   connection and per direction).  The text format is specified in
   Section 6.2.

   Sections 12 and 13 list some basic Text key=value pairs, some of
   which can be used in Login Requests/Responses and some in Text
   Requests/Responses.

   A key=value pair can span Text Request or Text Response boundaries.
   A key=value pair can start in one PDU and continue on the next.  In
   other words, the end of a PDU does not necessarily signal the end of
   a key=value pair.

   The target responds by sending its response back to the initiator.
   The response text format is similar to the request text format.  The
   Text Response MAY refer to key=value pairs presented in an earlier
   Text Request, and the text in the request may refer to earlier
   responses.

   Section 6.2 details the rules for the Text Requests and Responses.

   Text operations are usually meant for parameter setting/negotiations
   but can also be used to perform some long-lasting operations.

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   Text operations that take a long time should be placed in their own
   Text Request.

11.11.  Text Response

   The Text Response PDU contains the target's responses to the
   initiator's Text Request.  The format of the Text field matches that
   of the Text Request.

   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|.|.| 0x24      |F|C| Reserved                                  |
     +---------------+---------------+---------------+---------------+
    4|TotalAHSLength | DataSegmentLength                             |
     +---------------+---------------+---------------+---------------+
    8| LUN or Reserved                                               |
     +                                                               +
   12|                                                               |
     +---------------+---------------+---------------+---------------+
   16| Initiator Task Tag                                            |
     +---------------+---------------+---------------+---------------+
   20| Target Transfer Tag or 0xffffffff                             |
     +---------------+---------------+---------------+---------------+
   24| StatSN                                                        |
     +---------------+---------------+---------------+---------------+
   28| ExpCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   32| MaxCmdSN                                                      |
     +---------------+---------------+---------------+---------------+
   36/ Reserved                                                      /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
   48| Header-Digest (optional)                                      |
     +---------------+---------------+---------------+---------------+
     / DataSegment (Text)                                            /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
     | Data-Digest (optional)                                        |
     +---------------+---------------+---------------+---------------+

11.11.1.  F (Final) Bit

   When set to 1, in response to a Text Request with the Final bit set
   to 1, the F bit indicates that the target has finished the whole
   operation.  Otherwise, if set to 0 in response to a Text Request with
   the Final Bit set to 1, it indicates that the target has more work to

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   do (invites a follow-on Text Request).  A Text Response with the
   F bit set to 1 in response to a Text Request with the F bit set to 0
   is a protocol error.

   A Text Response with the F bit set to 1 MUST NOT contain key=value
   pairs that may require additional answers from the initiator.

   A Text Response with the F bit set to 1 MUST have a Target Transfer
   Tag field set to the reserved value 0xffffffff.

   A Text Response with the F bit set to 0 MUST have a Target Transfer
   Tag field set to a value other than the reserved value 0xffffffff.

11.11.2.  C (Continue) Bit

   When set to 1, this bit indicates that the text (set of key=value
   pairs) in this Text Response is not complete (it will be continued on
   subsequent Text Responses); otherwise, it indicates that this Text
   Response ends a set of key=value pairs.  A Text Response with the
   C bit set to 1 MUST have the F bit set to 0.

11.11.3.  Initiator Task Tag

   The Initiator Task Tag matches the tag used in the initial Text
   Request.

11.11.4.  Target Transfer Tag

   When a target has more work to do (e.g., cannot transfer all the
   remaining text data in a single Text Response or has to continue the
   negotiation) and has enough resources to proceed, it MUST set the
   Target Transfer Tag to a value other than the reserved value
   0xffffffff.  Otherwise, the Target Transfer Tag MUST be set to
   0xffffffff.

   When the Target Transfer Tag is not 0xffffffff, the LUN field may be
   significant.

   The initiator MUST copy the Target Transfer Tag and LUN in its next
   request to indicate that it wants the rest of the data.

   When the target receives a Text Request with the Target Transfer Tag
   set to the reserved value 0xffffffff, it resets its internal
   information (resets state) associated with the given Initiator Task
   Tag (restarts the negotiation).

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   When a target cannot finish the operation in a single Text Response
   and does not have enough resources to continue, it rejects the Text
   Request with the appropriate Reject code.

   A target may reset its internal state associated with an Initiator
   Task Tag (the current negotiation state) as expressed through the
   Target Transfer Tag if the initiator fails to continue the exchange
   for some time.  The target may reject subsequent Text Requests with
   the Target Transfer Tag set to the "stale" value.

11.11.5.  StatSN

   The target StatSN variable is advanced by each Text Response sent.

11.11.6.  Text Response Data

   The data lengths of a Text Response MUST NOT exceed the iSCSI
   initiator MaxRecvDataSegmentLength (a parameter that is negotiated
   per connection and per direction).

   The text in the Text Response Data is governed by the same rules as
   the text in the Text Request Data (see Section 11.11.2).

   Although the initiator is the requesting party and controls the
   request-response initiation and termination, the target can offer
   key=value pairs of its own as part of a sequence and not only in
   response to the initiator.

11.12.  Login Request

   After establishing a TCP connection between an initiator and a
   target, the initiator MUST start a Login Phase to gain further access
   to the target's resources.

   The Login Phase (see Section 6.3) consists of a sequence of Login
   Requests and Login Responses that carry the same Initiator Task Tag.

   Login Requests are always considered as immediate.

Top      Up      ToC       Page 197 
   Byte/     0       |       1       |       2       |       3       |
      /              |               |               |               |
     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
     +---------------+---------------+---------------+---------------+
    0|.|1| 0x03      |T|C|.|.|CSG|NSG| Version-max   | Version-min   |
     +---------------+---------------+---------------+---------------+
    4|TotalAHSLength | DataSegmentLength                             |
     +---------------+---------------+---------------+---------------+
    8| ISID                                                          |
     +                               +---------------+---------------+
   12|                               | TSIH                          |
     +---------------+---------------+---------------+---------------+
   16| Initiator Task Tag                                            |
     +---------------+---------------+---------------+---------------+
   20| CID                           | Reserved                      |
     +---------------+---------------+---------------+---------------+
   24| CmdSN                                                         |
     +---------------+---------------+---------------+---------------+
   28| ExpStatSN or Reserved                                         |
     +---------------+---------------+---------------+---------------+
   32| Reserved                                                      |
     +---------------+---------------+---------------+---------------+
   36| Reserved                                                      |
     +---------------+---------------+---------------+---------------+
   40/ Reserved                                                      /
    +/                                                               /
     +---------------+---------------+---------------+---------------+
   48/ DataSegment - Login Parameters in Text Request Format         /
    +/                                                               /
     +---------------+---------------+---------------+---------------+

11.12.1.  T (Transit) Bit

   When set to 1, this bit indicates that the initiator is ready to
   transit to the next stage.

   If the T bit is set to 1 and the NSG is set to FullFeaturePhase, then
   this also indicates that the initiator is ready for the Login
   Final-Response (see Section 6.3).

11.12.2.  C (Continue) Bit

   When set to 1, this bit indicates that the text (set of key=value
   pairs) in this Login Request is not complete (it will be continued on
   subsequent Login Requests); otherwise, it indicates that this Login
   Request ends a set of key=value pairs.  A Login Request with the
   C bit set to 1 MUST have the T bit set to 0.

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11.12.3.  CSG and NSG

   Through these fields -- Current Stage (CSG) and Next Stage (NSG) --
   the Login negotiation requests and responses are associated with a
   specific stage in the session (SecurityNegotiation,
   LoginOperationalNegotiation, FullFeaturePhase) and may indicate the
   next stage to which they want to move (see Section 6.3).  The Next
   Stage value is only valid when the T bit is 1; otherwise, it is
   reserved.

   The stage codes are:

      0 - SecurityNegotiation

      1 - LoginOperationalNegotiation

      3 - FullFeaturePhase

   All other codes are reserved.

11.12.4.  Version

   The version number for this document is 0x00.  Therefore, both
   Version-min and Version-max MUST be set to 0x00.

11.12.4.1.  Version-max

   Version-max indicates the maximum version number supported.

   All Login Requests within the Login Phase MUST carry the same
   Version-max.

   The target MUST use the value presented with the first Login Request.

11.12.4.2.  Version-min

   All Login Requests within the Login Phase MUST carry the same
   Version-min.  The target MUST use the value presented with the first
   Login Request.


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