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rfc:rfc7144

Internet Engineering Task Force (IETF) F. Knight Request for Comments: 7144 NetApp Category: Standards Track M. Chadalapaka ISSN: 2070-1721 Microsoft

                                                            April 2014
          Internet Small Computer System Interface (iSCSI)
                        SCSI Features Update

Abstract

 Internet Small Computer System Interface (iSCSI) is a SCSI
 transport protocol that maps the SCSI family of protocols onto
 TCP/IP.  The iSCSI protocol as specified in RFC 7143 (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 RFC 7143.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by
 the Internet Engineering Steering Group (IESG).  Further
 information on Internet Standards is available in Section 2 of
 RFC 5741.
 Information about the current status of this document, any
 errata, and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7144.

Knight & Chadalapaka Standards Track [Page 1] RFC 7144 iSCSI SCSI Features Update April 2014

Copyright Notice

 Copyright (c) 2014 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.

Knight & Chadalapaka Standards Track [Page 2] RFC 7144 iSCSI SCSI Features Update April 2014

Table of Contents

 1. Introduction ....................................................4
 2. Definitions, Acronyms, and Document Summary .....................4
    2.1. Definitions ................................................4
    2.2. Acronyms ...................................................4
    2.3. New Semantics ..............................................4
 3. Terminology Mapping .............................................5
 4. New Feature Use .................................................7
    4.1. Negotiation of New Feature Use .............................7
    4.2. Impact on Standard INQUIRY Data - iSCSI Version
         Descriptors ................................................8
 5. SCSI Commands ...................................................9
    5.1. SCSI Command Additions .....................................9
         5.1.1. Command Priority (Byte 2) ..........................10
    5.2. SCSI Response Additions ...................................11
         5.2.1. Status Qualifier ...................................12
         5.2.2. Data Segment - Sense and Response Data Segment .....12
 6. Task Management Functions ......................................13
    6.1. Task Management Function Request PDU ......................13
    6.2. Existing Task Management Functions ........................14
    6.3. Task Management Function Additions ........................14
         6.3.1. LUN Field ..........................................15
         6.3.2. Referenced Task Tag ................................16
         6.3.3. RefCmdSN ...........................................16
    6.4. Task Management Function Responses ........................17
         6.4.1. Task Management Function Response PDU ..............17
         6.4.2. Task Management Function Response Additions ........18
    6.5. Task Management Requests Affecting Multiple Tasks .........19
 7. Login/Text Operational Text Keys ...............................19
    7.1. New Operational Text Keys .................................19
         7.1.1. iSCSIProtocolLevel .................................19
 8. Security Considerations ........................................20
 9. IANA Considerations ............................................21
 10. References ....................................................24
    10.1. Normative References .....................................24
    10.2. Informative References ...................................24
 11. Acknowledgements ..............................................24

Knight & Chadalapaka Standards Track [Page 3] RFC 7144 iSCSI SCSI Features Update April 2014

1. Introduction

 The original iSCSI protocol [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 RFC 7143; this document may also be used as a
 companion document to the combination of [RFC3720] and [RFC5048],
 although both of those RFCs have been obsoleted by [RFC7143].
 For more information on the SCSI Architecture Model and SCSI Primary
 Commands - 4, contact the INCITS T10 Technical Committee for SCSI
 Storage Interfaces at <http://www.t10.org>.

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

 ACA      Auto Contingent Allegiance
 AHS      Additional Header Segment
 ISID     Initiator Session Identifier
 LU       Logical Unit
 PDU      Protocol Data Unit
 SAM-5    SCSI Architecture Model - 5 (see [SAM5])
 TSIH     Target Session Identifying Handle

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:  New feature use
                New features need negotiation for use.  The
                negotiation may have an impact on standard INQUIRY
                data.

Knight & Chadalapaka Standards Track [Page 4] RFC 7144 iSCSI SCSI Features Update April 2014

    Section 5:  New command operations
                The PRI field for SCSI command priority has been added
                to the SCSI Command PDU (see Section 5.1.1).  The
                Status Qualifier field has been added to the SCSI
                Response PDU (see Section 5.2.1).  Sense data may be
                returned (via Autosense) for any SCSI status, not just
                CHECK CONDITION (see Section 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 Section 6.3).  A new
                "Function succeeded" response has been added (see
                Section 6.4.2).
    Section 7:  New negotiation key
                A new negotiation key has been added to enable the use
                of the new features in Sections 5 and 6.

3. Terminology Mapping

 The iSCSI model (defined in [RFC7143]) 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:

Knight & Chadalapaka Standards Track [Page 5] RFC 7144 iSCSI SCSI Features Update April 2014

     Terminology in RFC 7143     | Terminology in SAM-5
   +-----------------------------+---------------------------+
   | 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        | SCSI Initiator Port       |
   | Identifier; (i.e., iSCSI    | Identifier                |
   | Node Name + ,,,i, + ISID)** |                           |
   +-----------------------------+---------------------------+
   | iSCSI Initiator Port Name;  | SCSI Initiator Port Name  |
   | (i.e., iSCSI Node Name +    |                           |
   | ,,,i, + ISID)**             |                           |
   +-----------------------------+---------------------------+
   | iSCSI Target Node           | SCSI Target Device        |
   +-----------------------------+---------------------------+
   | iSCSI Target Name           | SCSI Device Name          |
   +-----------------------------+---------------------------+
   | iSCSI Target Port           | SCSI Target Port          |
   | Identifier; (i.e., iSCSI    | Identifier                |
   | Node Name + ,,,t, +         |                           |
   | Target Portal Group Tag)**  |                           |
   +-----------------------------+---------------------------+
   | iSCSI Target Port Name;     | SCSI Target Port Name     |
   | (i.e., iSCSI Node Name +    |                           |
   | ,,,t, + Target Portal       |                           |
   | Group Tag)**                |                           |
   +-----------------------------+---------------------------+
   | iSCSI Target Portal Group   | SCSI Target Port          |
   +-----------------------------+---------------------------+
   | iSCSI Initiator Name +      | I_T Nexus Identifier      |
   | ',i,' + ISID + iSCSI        |                           |
   | Target Name + ',t,' +       |                           |
   | Target Portal Group Tag     |                           |
   +-----------------------------+---------------------------+
   | Target Portal Group Tag     | Relative Port ID          |
   +-----------------------------+---------------------------+
  • * The text encoding of the ISID value and the Target Portal Group

Tag value includes an initial ,,0X or ,,0x (see [RFC7143]).

Knight & Chadalapaka Standards Track [Page 6] RFC 7144 iSCSI SCSI Features Update April 2014

 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.
  1. —————————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)                    |
+--------------------------------------------------------------------+

4. New Feature Use

4.1. Negotiation of New Feature Use

 The iSCSIProtocolLevel operational text key (see Section 7.1.1)
 containing a value of "2" MUST be negotiated to enable the use of
 features described in this RFC.
 This is an iSCSI negotiation mechanism that enabled iSCSI support for
 corresponding SCSI capabilities (see [SAM5] and [SPC4]).  For this
 reason, negotiation of this key to a value of "2" is necessary but
 not sufficient for use of the SCSI capabilities enabled by the iSCSI
 features in this RFC.

Knight & Chadalapaka Standards Track [Page 7] RFC 7144 iSCSI SCSI Features Update April 2014

 For example, an iSCSI implementation may negotiate this new key to
 "2" but respond to the new task management functions (see Section
 6.3) with "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 (as such a reject would
 report an iSCSI protocol error).

4.2. Impact on Standard INQUIRY Data - iSCSI Version Descriptors

 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.)
 In support of this functionality, INCITS Technical Committee T10,
 which is responsible for SCSI standards, has assigned SCSI version
 descriptor codes 0961h-097Fh to RFC 7144 for IANA to manage via the
 values 1-31 of the iSCSIProtocolLevel key; see Section 9.  The "No
 version claimed" description for the value 0 of the
 iSCSIProtocolLevel key corresponds to the existing T10 assignment of
 the 0960h SCSI version descriptor code to "iSCSI (no version
 claimed)" -- for this reason, the assignment of the value 0 in the
 IANA registry for the iSCSIProtocolLevel key must not be changed.

Knight & Chadalapaka Standards Track [Page 8] RFC 7144 iSCSI SCSI Features Update April 2014

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)                                        /
   +---------------+---------------+---------------+---------------+
 The SCSI Command PDU above is duplicated from [RFC7143] for reference
 to show the PRI field.  For any field other than the PRI field, the
 text in [RFC7143] supersedes the text in Section 5.1 of this document
 in the event the two documents conflict.

Knight & Chadalapaka Standards Track [Page 9] RFC 7144 iSCSI SCSI Features Update April 2014

5.1.1. Command Priority (Byte 2)

 The Command Priority (PRI) is a four-bit field that specifies the
 relative scheduling importance of this command in relation to other
 commands already in the task set with SIMPLE task attributes (see
 [SAM5]).
 Section 11 ("iSCSI PDU Formats") of [RFC7143] 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".
 This field MUST be ignored by iSCSI targets unless the
 iSCSIProtocolLevel text key with a value of "2" as defined in Section
 7.1.1 was negotiated on the session.
 See [SAM5] for additional considerations on the use of the Command
 Priority field.

Knight & Chadalapaka Standards Track [Page 10] RFC 7144 iSCSI SCSI Features Update April 2014

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)                                        |
    +---------------+---------------+---------------+---------------+
 The SCSI Response PDU above is duplicated from [RFC7143] for
 reference to show the Status Qualifier field.  For any field other
 than the Status field, the Status Qualifier field, and the Data
 Segment - Sense and Response Data Segment field, the text in
 [RFC7143] supersedes the text in Section 5.2 of this document in the
 event the two documents conflict.

Knight & Chadalapaka Standards Track [Page 11] RFC 7144 iSCSI SCSI Features Update April 2014

5.2.1. Status Qualifier

 The Status Qualifier provides additional status information (see
 [SAM5]).
 As defined in Section 11 ("iSCSI PDU Formats") of [RFC7143],
 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" 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" as defined in Section 7.1.1 was
 negotiated on the session.

5.2.2. Data Segment - Sense and Response Data Segment

 Section 11.4.7 of [RFC7143] 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
 [RFC7143] 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" 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.

Knight & Chadalapaka Standards Track [Page 12] RFC 7144 iSCSI SCSI Features Update April 2014

6. Task Management Functions

6.1. Task Management Function Request PDU

  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)                                     |
    +                                                               +
  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)                                      |
    +---------------+---------------+---------------+---------------+
 The Task Management Function Request PDU above is duplicated from
 [RFC7143] for reference only.  [RFC7143] supersedes the text in
 Sections 6.1 and 6.2 of this document in the event the two documents
 conflict.

Knight & Chadalapaka Standards Track [Page 13] RFC 7144 iSCSI SCSI Features Update April 2014

6.2. Existing Task Management Functions

 Section 11.5 of [RFC7143] defines the semantics used to request that
 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

6.3. Task Management Function Additions

 Additional task management function codes are listed below.  For a
 more detailed description of SCSI task management, see [SAM5].
    9  - QUERY TASK - determine if the command identified by the
       Referenced Task Tag field is present in the task set.
    10 - QUERY TASK SET - determine if any command 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 (see
       [SAM5]) for 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" 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 6.4.2).
 For all of the task management functions detailed in this section,
 the Task Management Function Response MUST be returned as detailed in
 Section 6.4.

Knight & Chadalapaka Standards Track [Page 14] RFC 7144 iSCSI SCSI Features Update April 2014

 The iSCSI target MUST ensure that no responses for the commands
 covered by a task management function are sent to the iSCSI initiator
 port after the Task Management response except for commands 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".
 For the I_T NEXUS RESET function, the target device MUST respond to
 the function as defined in [SAM5].  Each logical unit accessible via
 the receiving I_T NEXUS MUST behave as dictated by the I_T nexus loss
 function in [SAM5] 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 values 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 [RFC7143], which in turn
 triggers the I_T nexus loss notification to the SCSI layer as
 described in [RFC7143].

6.3.1. 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.

Knight & Chadalapaka Standards Track [Page 15] RFC 7144 iSCSI SCSI Features Update April 2014

6.3.2. Referenced Task Tag

 The Reference Task Tag is 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.

6.3.3. 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
 11.6.1 of [RFC7143] when the task identified by the Referenced Task
 Tag field is not in the task set.

Knight & Chadalapaka Standards Track [Page 16] RFC 7144 iSCSI SCSI Features Update April 2014

6.4. Task Management Function Responses

6.4.1. Task Management Function Response PDU

  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 11.6 of [RFC7143] defines the semantics used for responses to
 SCSI task management functions.  The following responses are defined
 in [RFC7143]:
    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

Knight & Chadalapaka Standards Track [Page 17] RFC 7144 iSCSI SCSI Features Update April 2014

 The Task Management Function Response PDU above and the list of task
 management function responses above are duplicated from [RFC7143] for
 reference only.  [RFC7143] supersedes the text in section 6.4.1 of
 this document in the event the two documents conflict.
 Responses to new task management functions (see Section 6.4.2) 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.

6.4.2. 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 [SAM5].
 The Task Management Function Response of "Function succeeded" MUST be
 supported by an initiator that sends any of the new task management
 functions (see Section 6.3).
 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 6.3 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 [SAM5]) for
 this SCSI task management function may not be reliably delivered to
 the issuing initiator port.

Knight & Chadalapaka Standards Track [Page 18] RFC 7144 iSCSI SCSI Features Update April 2014

 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".

6.5. 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 included
 in that section by defining the tasks affected by the I_T NEXUS RESET
 function.
    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.
 Sections 4.1.2 and 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.

Knight & Chadalapaka Standards Track [Page 19] RFC 7144 iSCSI SCSI Features Update April 2014

 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.  Features using this key are
 expected to be cumulative.
 An iSCSIProtocolLevel key negotiated to "0" indicates that the
 implementation does not claim a specific iSCSI protocol level.
 An iSCSIProtocolLevel key negotiated to "1" indicates that the
 implementation claims compliance with [RFC7143].
 An iSCSIProtocolLevel key negotiated to "2" 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.

8. Security Considerations

 Command priorities are relative values, not absolute values (see
 [SAM5], and affect collections of commands, not necessarily
 individual commands (see [SAM5]).  If command priority is supported,
 it should be implemented in a fashion that avoids unwanted reduction
 or denial of service.
 All the iSCSI-related security text in [RFC3723] is directly
 applicable to this document.  The security text in [RFC7143] is
 directly applicable as well.

Knight & Chadalapaka Standards Track [Page 20] RFC 7144 iSCSI SCSI Features Update April 2014

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 Task Management Function
    Codes"
    The following entries have been added:
       9  - QUERY TASK, RFC 7144
       10 - QUERY TASK SET, RFC 7144
       11 - I_T NEXUS RESET, RFC 7144
       12 - QUERY ASYNCHRONOUS EVENT, RFC 7144
       13-127 - Unassigned
 2. iSCSI Login/Text Keys
    Name of the existing registry: "iSCSI Login/Text Keys"
    Fields to record in the registry: Assigned value and its
    associated RFC reference.
    The following entry has been added:
       iSCSIProtocolLevel,  RFC 7144
 IANA has created the following iSCSI-related registries.
 3.  iSCSI Protocol Level
    Name of new registry: "iSCSI Protocol Level"
    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.

Knight & Chadalapaka Standards Track [Page 21] RFC 7144 iSCSI SCSI Features Update April 2014

    Assignment policy:
    The assignments of these values must be coordinated with the
    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).
    Special care must be taken in the assignment of new values in this
    registry.  Compatibility and interoperability will be adversely
    impacted if proper care is not exercised.  Features using this key
    are expected to be cumulative.  For example, since this document
    explicitly lists only value 2 for the features listed in this
    document, it is expected that a new RFC assigning value 3 will
    also have the features listed in this RFC, and therefore such an
    RFC is expected to either revise or replace this RFC.  Assignments
    that do not follow this policy should be reviewed and approved by
    the INCITS T10 committee.
    3-31: range available to IANA for assignment in this registry.
    Fields to record in the registry: Assigned value, description, and
    its associated RFC reference.
    The following entries have been added:
       Value  Description         Reference
        0     No version claimed  RFC 7144
        1     RFC 7143            [RFC7143]
        2     RFC 7144            RFC 7144
        3-31  Unassigned
    Allocation Policy: Expert Review and Standards Action [RFC5226]
 4.  iSCSI Task Management Function Response Codes
    Name of new registry: "iSCSI Task Management Function Response
    Codes"
    Namespace details: Numerical values that can fit in 8 bits.

Knight & Chadalapaka Standards Track [Page 22] RFC 7144 iSCSI SCSI Features Update April 2014

    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.
    8-254: Range available to IANA for assignment in this registry.
    Fields to record in the registry: Assigned value, Operation Name,
    and its associated RFC reference.
    The following entries have been added:
       0 - Function complete, [RFC7143]
       1 - Task does not exist, [RFC7143]
       2 - LUN does not exist, [RFC7143]
       3 - Task still allegiant, [RFC7143]
       4 - Task allegiance reassignment not supported, [RFC7143]
       5 - Task management function not supported, [RFC7143]
       6 - Function authorization failed, [RFC7143]
       7 - Function succeeded, RFC 7144
       8-254 - Unassigned
       255 - Function rejected, [RFC7143]
    Allocation Policy: Standards Action [RFC5226]

Knight & Chadalapaka Standards Track [Page 23] RFC 7144 iSCSI SCSI Features Update April 2014

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.
 [RFC3723]  Aboba, B., Tseng, J., Walker, J., Rangan, V., and F.
            Travostino, "Securing Block Storage Protocols over IP",
            RFC 3723, April 2004.
 [RFC5048]  Chadalapaka, M., Ed., "Internet Small Computer System
            Interface (iSCSI) Corrections and Clarifications", RFC
            5048, October 2007.
 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            May 2008.
 [RFC7143]  Chadalapaka, M., Satran, J., Meth, K., and D. Black,
            "Internet Small Computer System Interface (iSCSI) Protocol
            (Consolidated)", RFC 7143, April 2014.
 [SAM2]     INCITS Technical Committee T10, "SCSI Architecture Model -
            2 (SAM-2)", ANSI INCITS 366-2003, ISO/IEC 14776-412, 2003.
 [SAM5]     INCITS Technical Committee T10, "SCSI Architecture Model -
            5 (SAM-5)", T10/BSR INCITS 515 rev 04, Committee Draft.
 [SPC4]     INCITS Technical Committee T10, "SCSI Primary Commands -
            4", ANSI INCITS 513-201x.

10.2. Informative References

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

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
 authors acknowledge the contributions of the entire working group and
 other IETF reviewers.

Knight & Chadalapaka Standards Track [Page 24] RFC 7144 iSCSI SCSI Features Update April 2014

 The following individuals directly contributed to identifying issues
 and/or suggesting resolutions to the issues clarified in this
 document: David Black, Rob Elliott.  This document benefited from all
 of these contributions.

Authors' 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

Knight & Chadalapaka Standards Track [Page 25]

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