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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 7144

Storage Maintenance (StorM) Working Group            Frederick Knight
Internet Draft                                                 NetApp
Intended status: Standards Track                       M. Chadalapaka
Expires: February 2012                                      Microsoft
                                                          August 2011


Internet Small Computer Systems Interface (iSCSI) SCSI Architecture
                          Features Update
                 draft-ietf-storm-iscsi-sam-04.txt

Abstract

   Internet Small Computer Systems Interface (iSCSI) is a SCSI
   transport protocol that maps the SCSI family of protocols onto
   TCP/IP. The iSCSI protocol as specified in [draft-ietf-storm-
   iscsi-cons-xx] (and as previously specified by the combination
   of RFC 3720 and RFC 5048) is based on the SAM-2 (SCSI
   Architecture Model - 2) version of the SCSI family of
   protocols. This document defines enhancements to the iSCSI
   protocol to support certain additional features of the SCSI
   protocol that were defined in SAM-3, SAM-4, and SAM-5.

   This document is a companion document to [draft-ietf-storm-
   iscsi-cons-xx].

      --------------------------------------------------------
      RFC EDITORS NOTE: The above references to [draft-ietf-storm-
      iscsi-cons-xx] should reference the RFC number assigned to
      that document, and this note should be removed.
      --------------------------------------------------------

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other
   documents at any time. It is inappropriate to use Internet-
   Drafts as reference material or to cite them other than as "work
   in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire February, 2012.

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Copyright Notice

    Copyright (c) 2011 IETF Trust and the persons identified as the
    document authors. All rights reserved.

    This document is subject to BCP 78 and the IETF Trust's Legal
    Provisions Relating to IETF Documents
    (http://trustee.ietf.org/license-info) in effect on the date of
    publication of this document. Please review these documents
    carefully, as they describe your rights and restrictions with
    respect to this document. Code Components extracted from this
    document must include Simplified BSD License text as described in
    Section 4.e of the Trust Legal Provisions and are provided
    without warranty as described in the Simplified BSD License.

Table of Contents

1   Introduction.................................................. 3
2   Definitions, Acronyms, and Document Summary................... 3
  2.1     Definitions ............................................ 3
  2.2     Acronyms ............................................... 3
  2.3     New Semantics .......................................... 3
3   Terminology Mapping........................................... 4
4   Negotiation of New Feature Use................................ 7
5   SCSI Commands................................................. 8
  5.1     SCSI Command Additions ................................. 8
    5.1.1     Command Priority (byte 2) .......................... 8
  5.2     SCSI Response Additions ................................ 9
    5.2.1     Status Qualifier .................................. 10
    5.2.2     Data Segment - Sense and Response Data Segment .... 10
6   Task Management Functions.................................... 10
  6.1     Existing Task Management Functions .................... 10
  6.2     Task Management Function Additions .................... 10
    6.2.1     LUN field ......................................... 12
    6.2.2     Referenced Task Tag ............................... 12
    6.2.3     RefCmdSN .......................................... 12
  6.3     Task Management Function Responses .................... 13
    6.3.1     Task Management Function Response Additions ....... 14
  6.4     Task Management Requests Affecting Multiple Tasks ..... 14
7   Login/Text Operational Text Keys............................. 15
  7.1     New Operational Text Keys ............................. 15
    7.1.1     iSCSIProtocolLevel ................................ 15
8   Security Considerations...................................... 16
9   IANA Considerations.......................................... 16
10 References.................................................... 18
11 Acknowledgements.............................................. 19




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1.      Introduction

     The original [RFC3720] was built based on the [SAM2] model for
     SCSI. Several new features and capabilities have been added to
     the SCSI Architecture Model in the intervening years (at the time
     of publication of this document, SAM-5 was the current version of
     the SCSI Architecture Model). This document is not a complete
     revision of [RFC3720]. Instead, this document is intended as a
     companion document to [draft-ietf-storm-iscsi-cons-xx]; this
     document may also be used as a companion document to the
     combination of [RFC3720] and [RFC5048], although both of those
     RFCs have been obsolete by [draft-ietf-storm-iscsi-cons-xx].

        --------------------------------------------------------
        RFC EDITORS NOTE: The above references to [draft-ietf-storm-
        iscsi-cons-xx] should reference the RFC number assigned to
        that document, and this note should be removed.
        --------------------------------------------------------

2.      Definitions, Acronyms, and Document Summary

2.1     Definitions

     The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
     "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
     this document are to be interpreted as described in [RFC2119].

2.2     Acronyms

     ISID     Initiator Session Identifier
     LU       Logical Unit
     PDU      Protocol Data Unit
     SAM-4    SCSI Architecture Model - 4 (see [SAM4])
     SAM-5    SCSI Architecture Model - 5 (see [SAM5])
     TMF      Task Management Function

2.3     New Semantics

      This document specifies new iSCSI semantics.    This section
      summarizes the contents of the document.

        Section 3: The mapping of iSCSI objects to SAM-5 objects
                   The iSCSI node may contain both initiator and
                   target capabilities.

        Section 4: The protocol used to negotiate the use of the new
                   capabilities described in this document.

        Section 5: New Command operations
                   The PRI field for SCSI command priority has been
                   added to the SCSI command PDU (see 5.1.1).


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                   The Status Qualifier field has been added to the
                   SCSI response PDU (see 5.2.1).
                   Sense data may be returned (via autosense) for any
                   SCSI status, not just CHECK CONDITION (see 5.2.2).

       Section 6: New Task Management Functions
                  Four new task management functions (QUERY TASK,
                  QUERY TASK SET, I_T NEXUS RESET, and QUERY
                  ASYNCHRONOUS EVENT have been added (see 6.2).
                  A new "function succeeded" response has been added
                  (see 6.3.1).

       Section 7: New Negotiation key
                  A new negotiation key has been added to enable the
                  use of the new features in section 5 and section 6.

3.      Terminology Mapping

     The iSCSI model (defined in [RFC3720]) uses different terminology
     than the SCSI Architecture Model. In some cases, iSCSI uses
     multiple terms to describe what in the SCSI Architecture Model is
     described with a single term. The iSCSI terms and SAM-5 terms
     are not necessarily equivalent, but rather, the iSCSI terms
     represent examples of the objects or classes described in SAM-5
     as follows:




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  +-----------------------------+---------------------------+
  | RFCxxx Terminology          | SAM-5 Terminology         |
  +-----------------------------+---------------------------+
  | Network Entity              | none                      |
  +-----------------------------+---------------------------+
  | iSCSI Node                  | SCSI Device               |
  +-----------------------------+---------------------------+
  | iSCSI Name                  | SCSI Device Name          |
  +-----------------------------+---------------------------+
  | iSCSI Node Name             | SCSI Device Name          |
  +-----------------------------+---------------------------+
  | iSCSI Initiator Node        | SCSI Initiator Device     |
  +-----------------------------+---------------------------+
  | iSCSI Initiator Name        | SCSI Device Name          |
  +-----------------------------+---------------------------+
  | iSCSI Initiator Port Name   | SCSI Initiator Port Name  |
  | iSCSI Node Name + ',i,' + |                             |
  | ISID                        |                           |
  +-----------------------------+---------------------------+
  | iSCSI Target Node           | SCSI Target Device        |
  +-----------------------------+---------------------------+
  | iSCSI Target Name           | SCSI Device Name          |
  +-----------------------------+---------------------------+
  | iSCSI Target Port Name      | SCSI Target Port Name     |
  | iSCSI Node Name + ',t,' + |                             |
  | Target Portal Group Tag     |                           |
  +-----------------------------+---------------------------+
  | iSCSI Target Portal Group   | SCSI Target Port          |
  +-----------------------------+---------------------------+
  | iSCSI Initiator Node +      | SCSI Initiator Port       |
  | active ISID                 |                           |
  +-----------------------------+---------------------------+
  | iSCSI Initiator Name +      | I_T Nexus                 |
  | ',i,' + ISID, iSCSI Target |                            |
  |   Name + ',t,' + Portal     |                           |
  |   Group Tag                 |                           |
  +-----------------------------+---------------------------+
  | Target Portal Group Tag     | Relative Port ID          |
  +-----------------------------+---------------------------+

      --------------------------------------------------------
      RFC EDITORS NOTE: The above reference (in row 1) to [RFCxxx]
      should reference this RFC, and this note should be removed.
      --------------------------------------------------------




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  The following diagram shows an example of a combination target
  device and initiator device. Such a configuration may exist in a
  target device that implements a SCSI Copy Manager. This example
  shows how a session that shares Network Portals within a Portal
  Group may be established (see Target Portal Group 1). In
  addition, this example shows the Initiator using a different
  Portal Group than the Target Portal Group, but the Initiator
  Portal group sharing Network Portal A with the Target Portal
  Group.


   ----------------------------IP Network---------------------
           |               |                    |
      +----|---------------|-------+       +----|------------+
      | +----------+ +----------+  |       | +----------+    |
      | | Network  | | Network  |  |       | | Network  |    |
      | | Portal A | | Portal B |  |       | | Portal A |    |
      | +----------+ +----------+  |       | +----------+    |
      |    |    Target     |       |       |    | Initiator  |
      |    |    Portal     |       |       |    | Portal     |
      |    |    Group 1    |       |       |    | Group 2    |
      +----|---------------|-------+       +----|------------+
           |               |                    |
+----------|---------------|--------------------|--------------------+
| +--------|---------------|----+ +-------------|------------------+ |
| |+-------|---------------|---+| |+------------|-----------------+| |
| ||iSCSI Session (Target side)|| ||iSCSI Session (Initiator side)|| |
| ||                           || ||                              || |
| ||       (TSIH = 56)         || ||         (SSID = 48)          || |
| |+---------------------------+| |+------------------------------+| |
| |                             | |                                | |
| |     iSCSI Target Node       | |      iSCSI Initiator Node      | |
| +-----------------------------+ +--------------------------------+ |
|                          iSCSI Node                                |
|              (within Network Entity, not shown)                    |
+--------------------------------------------------------------------+




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4.      New Feature Use

4.1   Negotiation of New Feature Use

     The iSCSIProtocolLevel operational text key (see 7.1.1)
     containing a value of "2" or higher MUST be negotiated to enable
     the use of features described in this RFC.

     Note that an operational value of "2" or higher for this key on
     an iSCSI session does not influence the SCSI level features in
     any way on that I_T nexus. An operational value of "2" or higher
     for this key permits the iSCSI-related features defined in this
     document to be used on all connections on this iSCSI session.
     SCSI level hand-shakes (e.g. commands, mode pages) eventually
     determine the existence or lack of various SAM-5 features
     available for the I_T nexus between the two SCSI end points). To
     summarize, negotiation of this key to "2" or higher is a
     necessary but not a sufficient condition of SAM-5 compliant
     feature usage at the SCSI protocol level.

     For example, an iSCSI implementation may negotiate this new key
     to "2" but respond to the new task management functions (see 6.2)
     with a "Task management function not supported" (which indicates
     a SCSI error that prevents the function from being performed).
     In contrast, if the key is negotiated to "2", an iSCSI
     implementation MUST NOT reject a task management function request
     PDU that requests one of the new task management functions (such
     a reject would report an iSCSI protocol error).

4.2   Impact on standard INQUIRY data

     The negotiated value of the iSCSIProtocolLevel key is an
     increment from the base iSCSI version descriptor value
     (0960h)(see [SPC4]). If the SCSI device server returns an iSCSI
     version descriptor in the standard INQUIRY data, then the value
     returned in that iSCSI version descriptor MUST be set to the sum
     of the base value (0960h) plus the negotiated value of the
     iSCSIProtocolLevel key (for example, if the negotiated
     iSCSIProtocolLevel=2, then if an iSCSI version descriptor is
     returned in the standard INQUIRY data it is set to 0962h).




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5.     SCSI Commands

5.1    SCSI Command Additions

     The format of the SCSI Command PDU is:

 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| 0x01      |F|R|W|. .|ATTR | PRI   | Reserved              |
   +---------------+---------------+---------------+---------------+
  4|TotalAHSLength | DataSegmentLength                             |
   +---------------+---------------+---------------+---------------+
  8| Logical Unit Number (LUN)                                     |
   +                                                               +
 12|                                                               |
   +---------------+---------------+---------------+---------------+
 16| Initiator Task Tag                                            |
   +---------------+---------------+---------------+---------------+
 20| Expected Data Transfer Length                                 |
   +---------------+---------------+---------------+---------------+
 24| CmdSN                                                         |
   +---------------+---------------+---------------+---------------+
 28| ExpStatSN                                                     |
   +---------------+---------------+---------------+---------------+
 32/ SCSI Command Descriptor Block (CDB)                           /
  +/                                                               /
   +---------------+---------------+---------------+---------------+
 48/ AHS (Optional)                                                /
   +---------------+---------------+---------------+---------------+
  x/ Header Digest (Optional)                                      /
   +---------------+---------------+---------------+---------------+
  y/ (DataSegment, Command Data) (Optional)                        /
  +/                                                               /
  +---------------+---------------+---------------+----------------+
  z/ Data Digest (Optional)                                        /
  +---------------+---------------+---------------+----------------+

5.1.1 Command Priority (byte 2)

     The Command Priority (PRI) specifies the relative scheduling
     importance of this task in relation to other SIMPLE tasks already
     in the task set (see [SAM4]).

     Section 10, iSCSI PDU Formats of [RFC3720], requires that senders
     set this field to zero. A sender MUST NOT set this field to a
     value other than zero unless the iSCSIProtocolLevel text key
     defined in section 7.1.1 has been negotiated on the session with
     a value of "2" or higher.



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  This field MUST be ignored by iSCSI targets unless the
  iSCSIProtocolLevel text key with a value of "2" or higher as
  defined in section 7.1.1 was negotiated on the session.

5.2   SCSI Response Additions

  The format of the SCSI Response PDU is:

  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|.|.| 0x21      |1|. .|o|u|O|U|.| Response      | Status        |
    +---------------+---------------+---------------+---------------+
   4|TotalAHSLength | DataSegmentLength                             |
    +---------------+---------------+---------------+---------------+
   8| Status Qualifier              | Reserved                      |
    +---------------+---------------+---------------+---------------+
  12| Reserved                                                      |
    +---------------+---------------+---------------+---------------+
  16| Initiator Task Tag                                            |
    +---------------+---------------+---------------+---------------+
  20| SNACK Tag or Reserved                                         |
    +---------------+---------------+---------------+---------------+
  24| StatSN                                                        |
    +---------------+---------------+---------------+---------------+
  28| ExpCmdSN                                                      |
    +---------------+---------------+---------------+---------------+
  32| MaxCmdSN                                                      |
    +---------------+---------------+---------------+---------------+
  36| ExpDataSN or Reserved                                         |
    +---------------+---------------+---------------+---------------+
  40| Bidirectional Read Residual Count or Reserved                 |
    +---------------+---------------+---------------+---------------+
  44| Residual Count or Reserved                                    |
    +---------------+---------------+---------------+---------------+
  48| Header-Digest (Optional)                                      |
    +---------------+---------------+---------------+---------------+
    / Data Segment (Optional)                                       /
   +/                                                               /
    +---------------+---------------+---------------+---------------+
    | Data-Digest (Optional)                                        |
    +---------------+---------------+---------------+---------------+




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5.2.1 Status Qualifier

     The Status Qualifier provides additional status information (see
     [SAM4]).

     As defined in Section 10, iSCSI PDU Formats of [RFC3720],
     compliant senders already set this field to zero. Compliant
     senders MUST NOT set this field to a value other than zero unless
     the iSCSIProtocolLevel text key with a value of "2" or higher as
     defined in section 7.1.1 was negotiated on the session.

     This field MUST be ignored by receivers unless the
     iSCSIProtocolLevel text key with a value of "2" or higher as
     defined in section 7.1.1 was negotiated on the session.

5.2.2 Data Segment - Sense and Response Data Segment

     Section 10.4.7 of [RFC3720] specifies that iSCSI targets MUST
     support and enable autosense. If Status is CHECK CONDITION
     (0x02), then the Data Segment MUST contain sense data for the
     failed command. While [RFC3720] does not make any statements
     about the state of the Data Segment when the Status is not CHECK
     CONDITION (0x02)(i.e., the Data Segment is not prohibited from
     containing sense data when the Status is not CHECK CONDITION),
     negotiation of the iSCSIProtocolLevel text key with a value of
     "2" or higher as defined in section 7.1.1 explicitly indicates
     that the Data Segment MAY contain sense data at any time, no
     matter what value is set in the Status field.

6.         Task Management Functions

6.1        Existing Task Management Functions

     Section 10.5 of [RFC3720] defines the semantics used to request
     SCSI Task Management Functions be performed. The following task
     management functions are defined:

       1   -   ABORT TASK
       2   -   ABORT TASK SET
       3   -   CLEAR ACA
       4   -   CLEAR TASK SET
       5   -   LOGICAL UNIT RESET
       6   -   TARGET WARM RESET
       7   -   TARGET COLD RESET
       8   -   TASK REASSIGN

6.2        Task Management Function Additions

      Additional task Management function codes are listed below. For
      a more detailed description of SCSI task management, see [SAM5].



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     9 - QUERY TASK - determines if the task identified by the
     Referenced Task Tag field is present in the task set.

      10 - QUERY TASK SET - determine if any task is present in the
      task set for the I_T_L Nexus on which the task management
      function was received.

      11 - I_T NEXUS RESET - perform an I_T nexus loss function for
      the I_T nexus of each logical unit accessible through the I_T
      Nexus on which the task management function was received.

      12 - QUERY ASYNCHRONOUS EVENT - determine if there is a unit
      attention condition or a deferred error pending for the I_T_L
      nexus on which the task management function was received.

  These task management function requests MUST NOT be sent unless
  the iSCSIProtocolLevel text key with a value of "2" or higher as
  defined in section 7.1.1 was negotiated on the session.

  Any compliant initiator that sends any of the new task management
  functions defined in this section MUST also support all new task
  management function responses (as specified in section 6.3.1).

  For all of the task management functions detailed in this
  section, the Task Management function response MUST be returned
  as detailed in section 6.3 Task Management Function Response.

  The iSCSI target MUST ensure that no responses for the tasks
  covered by a task management function are sent to the iSCSI
  initiator after the Task Management response except for a task
  covered by a TASK REASSIGN, QUERY TASK, or QUERY TASK SET.

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

  If the connection is still active (it is not undergoing an
  implicit or explicit logout), QUERY TASK MUST be issued on the
  same connection to which the task to be queried 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 a
  QUERY TASK function request may be issued on another connection.
  This Task Management request will then establish a new allegiance
  for the command being queried.

  At the target a QUERY TASK function MUST NOT be executed on a
  Task Management request; such a request MUST result in Task
  Management response of "Function rejected".


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  For the I_T NEXUS RESET function, the target device MUST respond
  to the function as defined in [SAM4]. Each logical unit
  accessible via the receiving I_T NEXUS MUST behave as dictated by
  the I_T nexus loss function in [SAM4] for the I_T nexus on which
  the task management function was received. The target device
  MUST drop all connections in the session over which this function
  is received. Independent of the DefaultTime2Wait and
  DefaultTime2Retain value applicable to the session over which
  this function is received, the target device MUST consider each
  participating connection in the session to have immediately timed
  out, leading to FREE state. The resulting timeouts cause the
  session timeout event defined in [RFC3720], which in turn
  triggers the I_T nexus loss notification to the SCSI layer as
  described in [RFC3720].

6.2.1 LUN field

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

6.2.2 Referenced Task Tag

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

6.2.3 RefCmdSN

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

   For a QUERY TASK of a task created by non-immediate command
   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 10.6.1 of [RFC3720] when the task identified
   by the Referenced Task Tag field is not in the task set.




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6.3     Task Management Function Responses

 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| Additional Response Information               | Reserved      |
   +-----------------------------------------------+---------------+
 12| Reserved                                                      |
   +---------------+---------------+---------------+---------------+
 16| Initiator Task Tag                                            |
   +---------------+---------------+---------------+---------------+
 20| Reserved                                                      |
   +---------------+---------------+---------------+---------------+
 24| StatSN                                                        |
   +---------------+---------------+---------------+---------------+
 28| ExpCmdSN                                                      |
   +---------------+---------------+---------------+---------------+
 32| MaxCmdSN                                                      |
   +---------------+---------------+---------------+---------------+
 36/ Reserved                                                      /
  +/                                                               /
   +---------------+---------------+---------------+---------------+
 48| Header-Digest (Optional)                                      |
   +---------------+---------------+---------------+---------------+

      Section 10.6 of [RFC3720] defines the semantics used for
      responses to SCSI Task Management Functions. The following
      responses are defined in [RFC3720]:

        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.

      Responses to new task management functions (see 6.3.1) are listed
      below. In addition, a new task Management response is listed
      below. For a more detailed description of SCSI task management
      responses, see [SAM5].

      For the functions QUERY TASK, QUERY TASK SET, I_T NEXUS RESET,
      and QUERY ASYNCHRONOUS EVENT, the target performs the requested
      Task Management function and sends a Task Management response
      back to the initiator.

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6.3.1 Task Management Function Response Additions

  The new response is listed below:

      7 - Function succeeded.

  In symbolic terms Response value 7 maps to the SCSI service
  response of FUNCTION SUCCEEDED in [SAM4].

  The task management function response of "Function succeeded"
  MUST be supported by an initiator that sends any of the new task
  management functions (see 6.2).

  For the QUERY TASK function, if the specified task is in the task
  set, then the logical unit returns a Response value of Function
  succeeded and additional response information is returned as
  specified in [SAM5]. If the specified task is not in the task
  set, then the logical unit returns a Response value of Function
  complete.

  For the QUERY TASK SET function, if there is any command present
  in the task set from the specified I_T_L nexus, then the logical
  unit returns a Response value of Function succeeded. If there
  are no commands present in the task set from the specified I_T_L
  nexus, then the logical unit returns a Response value of Function
  complete.

  For the I_T NEXUS RESET function, after completion of the events
  described in section 6.2 for this function, the logical unit
  returns a Response value of Function complete. However, because
  the target drops all connections, the Service Response (defined
  by [SAM4]) for this SCSI task management function may not be
  reliably delivered to the issuing initiator port.

  For the QUERY ASYNCHRONOUS EVENT, if there is a unit attention
  condition or deferred error pending for the specified I_T_L
  nexus, then the logical unit returns a Response value of Function
  succeeded and additional response information is returned as
  specified in [SAM5]. If there is no unit attention or deferred
  error pending for the specified I_T_L nexus then the logical unit
  returns a Response value of Function complete.

6.4   Task Management Requests Affecting Multiple Tasks

  Section 4.1 of [RFC5048] defines the notion of "affected tasks"
  in multi-task abort scenarios. This section adds to the list
  include in that section by defining the tasks affected by the I_T
  NEXUS RESET function.




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         I_T NEXUS RESET: All outstanding tasks received on the I_T
            nexus on which the function request was received for all
            logical units accessible to the I_T nexus.

     Section 4.1.2 of [RFC5048] and section 4.1.3 of [RFC5048]
     identify semantics for task management functions that involve
     multi-task abort operations. If an iSCSI implementation supports
     the I_T NEXUS RESET function, it MUST also support the protocol
     behavior as defined in those sections and follow the sequence of
     actions as described in those sections when processing the I_T
     NEXUS RESET function.

7.       Login/Text Operational Text Keys

7.1      New Operational Text Keys

7.1.1 iSCSIProtocolLevel

     Use: LO, IO
     Irrelevant when: SessionType = Discovery
     Senders: Initiator and Target
     Scope: SW

     iSCSIProtocolLevel=<numerical-value-from-0-to-31>

     Default is 1.
     Result function is Minimum.

     This key is used to negotiate the use of iSCSI features that
     require different levels of protocol support (e.g., PDU formats,
     end node semantics) for proper operation.

     Negotiation of the iSCSIProtocolLevel key to a value
     corresponding to an RFC indicates that both negotiating parties
     are compliant to the RFC in question, and agree to support the
     corresponding PDU formats and semantics on that iSCSI session.
     An operational value of iSCSI ProtocolLevel = "x" on an iSCSI
     session requires that the iSCSI protocol semantics on that iSCSI
     session be a logical superset of the capabilities in all RFCs
     that have claimed values of an iSCSIProtocolLevel less than "x".

      An iSCSIProtocolLevel key negotiated to "0" indicates that the
      implementation does not claim a specific iSCSI protocol level.

      An iSCSIProtocolLevel key negotiated to "2" or higher is required
      to enable use of features defined in this RFC.

      If the negotiation answer is ignored by the acceptor, or the
      answer from the remote iSCSI end point is key=NotUnderstood, then
      the features defined in this RFC, and the features defined in any
      RFC requiring a key value greater than "2" MUST NOT be used.


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8.      Security Considerations

     At the time of writing this document does not introduce any new
     security considerations other than those described in [RFC3720].
     Consequently, all the iSCSI-related security text in [RFC3723] is
     also directly applicable to this document.

9.      IANA Considerations

     This document modifies or creates a number of iSCSI-related
     registries. The following iSCSI-related registries are modified:

     1. iSCSI Task Management Functions Codes

       Name of the existing registry: "iSCSI TMF Codes"

        Additional entries:

        9, QUERY TASK, [RFCxxx]

        10, QUERY TASK SET, [RFCxxx]

        11, I_T NEXUS RESET, [RFCxxx]

        12, QUERY ASYNCHRONOUS EVENT, [RFCxxx]

        ---------------------------------------------------------
        RFC EDITORS NOTE: The above reference to [RFCxxx] should
        reference this RFC, and this note should be removed.
        ---------------------------------------------------------

     2. iSCSI Login/Text Keys

        Name of the existing registry: "iSCSI Text Keys"

        Fields to record in the registry: Assigned value and its
        associated RFC reference:

        iSCSIProtocolLevel, [RFCxxx]

       ---------------------------------------------------------
       RFC EDITORS NOTE: The above references to [RFCxxx] should
       reference this RFC, and this note should be removed.
       ---------------------------------------------------------

     This document creates the following iSCSI-related registries for
     IANA to manage.

     3. iSCSI Protocol Level

       Name of new registry: "iSCSI Protocol Level"



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     Namespace details: Numerical values from 0 to 31

     Information that must be provided to assign a new value: An
     IESG-approved standards track specification defining the
     semantics and interoperability requirements of the proposed
     new value and the fields to be recorded in the registry.

     Assignment policy:

     The assignments of these values must be coordinated with the
     ANSI/INCITS T10 committee; therefore review by an expert that
     maintains an association with that committee is required prior
     to IESG approval of the associated specification. After
     creation of the registry, values are to be assigned
     sequentially (for example, any value greater than 4 will not
     be assigned until after the value 4 has been assigned).

     1 and 3-31: range reserved by IANA for assignment in this
     registry.

     Fields to record in the registry: Assigned value, and its
     associated RFC reference.

     0, [RFCxxx]

     2, [RFCxxx]

     ---------------------------------------------------------
     RFC EDITORS NOTE: The above references to [RFCxxx] should
     reference this RFC, and this note should be removed.
     ---------------------------------------------------------

     Allocation Policy:

     Expert review ([IANA]) and Standards Action ([IANA])

  4. iSCSI Task Management Response Codes

     Name of new registry: "iSCSI TMF Response Codes"

     Namespace details: Numerical values that can fit in 8 bits.

     Information that must be provided to assign a new value: An
     IESG-approved specification defining the semantics and
     interoperability requirements of the proposed new value and
     the fields to be recorded in the registry.

     Assignment policy:

     If the requested value is not already assigned, it may be
     assigned to the requester.



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       8-254: Range reserved by iANA for assignment in this registry.

       Fields to record in the registry: Assigned value, Operation
       Name, and its associated RFC reference.

       0x0, Function complete, [RFC3720]

       0x1, Task does not exist, [RFC3720]

       0x2, LUN does not exist, [RFC3720]

       0x3, Task still allegiant, [RFC3720]

       0x4, Task allegiance reassignment not supported, [RFC3720]

       0x5, Task management function not supported, [RFC3720]

       0x6, Function authorization failed, [RFC3720]

       0x7, Function succeeded, [RFCxxx]

       255, Function rejected, [RFC3720]

       ------------------------------------------------------------
       RFC EDITORS NOTE: The above reference to [RFCxxx] should
       reference this RFC, and this note should be removed.
       ------------------------------------------------------------

       Allocation Policy:

       Standards Action ([IANA])

10.    References

10.1   Normative References

  [RFC2119]      Bradner, S. "Key Words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.

  [RFC3720]      Satran, J., Meth, K., Sapuntzakis, C., Chadalapaka,
                 M., and E. Zeidner, "Internet Small Computer Systems
                 Interface (iSCSI)", RFC 3720, April 2004.

  [RFC3723]      Aboba, B., Tseng, J., Walker, J., Rangan, V., and
                 Travostino, F., "Securing Block Storage Protocols
                 over IP", RFC 3723, April 2004.

  [RFC5048]      Chadalapaka, M., "Internet Small Computer System
                 Interface (iSCSI) Corrections and Clarifications",
                 RFC 5048, October 2007.




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  [draft-ietf-storm-iscsi-cons-xx]   Chadalapaka, M., Satran, J.,
              Kalman, M., "iSCSI Protocol (consolidated)", RFC xxx,
              Date 2011.

       ------------------------------------------------------------
       RFC EDITORS NOTE: The above references to [draft-ietf-storm-
       iscsi-cons-xx] and [RFCxxx] should reference the RFC number
       assigned to that draft, and this note should be removed.
       ------------------------------------------------------------

   [IANA]        Narten, T. and H. Alvestrand, "Guidelines for Writing
                 an IANA Considerations Section in RFCs", BCP 26, RFC
                 5226, May 2008.

   [SAM2]        T10/1157D, SCSI Architecture Model - 2 (SAM-2).

   [SAM4]        ISO/IEC 14776-414, SCSI Architecture Model - 4 (SAM-
                 4).

   [SAM5]        T10/2104D rev r04, SCSI Architecture Model - 5 (SAM-
                 5), Committee Draft.

   [SPC4]        T10/1731D rev r23, SCSI Primary Commands - 4 (SPC-4),
                 Committee Draft.

10.2   Additional Reference Sources

   For more information on the SCSI Architecture Model, contact the
   T10 group at http://www.t10.org.

11.    Acknowledgements

  The Storage Maintenance (STORM) Working Group in the Transport
  Area of the IETF has been responsible for defining these
  additions to the iSCSI protocol (apart from other relevant IP
  Storage protocols). The editor acknowledges the contributions of
  the entire working group.
  The following individuals directly contributed to identifying
  [RFCxxx] issues and/or suggesting resolutions to the issues
  clarified in this document: David Black, Rob Elliott. This
  document benefited from all of these contributions.
       ------------------------------------------------------------
       RFC EDITORS NOTE: The above reference to [RFCxxx] should
       reference this RFC, and this note should be removed.
       ------------------------------------------------------------




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  Author's Addresses


  Frederick Knight
  7301 Kit Creek Road
  P.O. Box 13917
  Research Triangle Park, NC 27709, USA
  Phone: +1-919-476-5362
  Email: knight@netapp.com


  Mallikarjun Chadalapaka
  Microsoft
  One Microsoft Way
  Redmond, WA 98052 USA
  Email: cbm@chadalapaka.com




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