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rfc:rfc5048

Network Working Group M. Chadalapaka, Ed. Request for Comments: 5048 Hewlett-Packard Co. Updates: 3720 October 2007 Category: Standards Track

         Internet Small Computer System Interface (iSCSI)
                   Corrections and Clarifications

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 The Internet Small Computer System Interface (iSCSI) is a SCSI
 transport protocol and maps the SCSI architecture and command sets
 onto TCP/IP.  RFC 3720 defines the iSCSI protocol.  This document
 compiles the clarifications to the original protocol definition in
 RFC 3720 to serve as a companion document for the iSCSI implementers.
 This document updates RFC 3720 and the text in this document
 supersedes the text in RFC 3720 when the two differ.

Table of Contents

 1. Introduction ....................................................3
 2. Definitions, Acronyms, and Document Summary .....................3
    2.1. Definitions ................................................3
    2.2. Acronyms ...................................................4
    2.3. Clarifications, Changes, and New Semantics .................5
 3. iSCSI Semantics for SCSI Tasks ..................................7
    3.1. Residual Handling ..........................................7
         3.1.1. Overview ............................................7
         3.1.2. SCSI REPORT LUNS and Residual Overflow ..............7
    3.2. R2T Ordering ...............................................9
    3.3. Model Assumptions for Response Ordering ....................9
         3.3.1. Model Description ..................................10
         3.3.2. iSCSI Semantics with the Interface Model ...........10
         3.3.3. Current List of Fenced Response Use Cases ..........11
 4. Task Management ................................................12
    4.1. Requests Affecting Multiple Tasks .........................12
         4.1.1. Scope of Affected Tasks ............................12
         4.1.2. Clarified Multi-Task Abort Semantics ...............13
         4.1.3. Updated Multi-Task Abort Semantics .................14

Chadalapaka Standards Track [Page 1] RFC 5048 iSCSI Corrections and Clarifications October 2007

         4.1.4. Affected Tasks Shared across RFC 3720 and
                FastAbort Sessions .................................16
         4.1.5. Implementation Considerations ......................17
         4.1.6. Rationale behind the New Semantics .................17
 5. Discovery Semantics ............................................19
    5.1. Error Recovery for Discovery Sessions .....................19
    5.2. Reinstatement Semantics of Discovery Sessions .............19
         5.2.1. Unnamed Discovery Sessions .........................20
         5.2.2. Named Discovery Sessions ...........................20
    5.3. Target PDUs during Discovery ..............................20
 6. Negotiation and Others .........................................21
    6.1. TPGT Values ...............................................21
    6.2. SessionType Negotiation ...................................21
    6.3. Understanding NotUnderstood ...............................21
    6.4. Outstanding Negotiation Exchanges .........................22
 7. iSCSI Error Handling and Recovery ..............................22
    7.1. ITT .......................................................22
    7.2. Format Errors .............................................22
    7.3. Digest Errors .............................................22
    7.4. Message Error Checking ....................................23
 8. iSCSI PDUs .....................................................23
    8.1. Asynchronous Message ......................................23
    8.2. Reject ....................................................24
 9. Login/Text Operational Text Keys ...............................24
    9.1. TaskReporting .............................................24
 10. Security Considerations .......................................25
 11. IANA Considerations ...........................................26
    11.1. iSCSI-Related IANA Registries ............................26
    11.2. iSCSI Opcodes ............................................26
    11.3. iSCSI Login/Text Keys ....................................28
    11.4. iSCSI Asynchronous Events ................................30
    11.5. iSCSI Task Management Function Codes .....................31
    11.6. iSCSI Login Response Status Codes ........................32
    11.7. iSCSI Reject Reason Codes ................................34
    11.8. iSER Opcodes .............................................35
 12. References ....................................................36
    12.1. Normative References .....................................36
    12.2. Informative References ...................................36
 Acknowledgements ..................................................37

Chadalapaka Standards Track [Page 2] RFC 5048 iSCSI Corrections and Clarifications October 2007

1. Introduction

 Several iSCSI implementations have been built since [RFC3720] was
 published and the iSCSI community is now richer by the resulting
 implementation expertise.  The goal of this document is to leverage
 this expertise both to offer clarifications to the [RFC3720]
 semantics and to address defects in [RFC3720] as appropriate.  This
 document intends to offer critical guidance to implementers with
 regard to non-obvious iSCSI implementation aspects so as to improve
 interoperability and accelerate iSCSI adoption.  This document,
 however, does not purport to be an all-encompassing iSCSI how-to
 guide for implementers, nor a complete revision of [RFC3720].
 Instead, this document is intended as a companion document to
 [RFC3720] for the iSCSI implementers.
 iSCSI implementers are required to reference [RFC3722] and [RFC3723]
 in addition to [RFC3720] for mandatory requirements.  In addition,
 [RFC3721] also contains useful information for iSCSI implementers.
 The text in this document, however, updates and supersedes the text
 in [RFC3720] whenever there is such a question.

2. Definitions, Acronyms, and Document Summary

2.1. Definitions

 I/O Buffer
    A buffer that is used in a SCSI Read or Write operation so SCSI
    data may be sent from or received into that buffer.  For a read or
    write data transfer to take place for a task, an I/O Buffer is
    required on the initiator and at least one is required on the
    target.
 SCSI-Presented Data Transfer Length (SPDTL)
    SPDTL is the aggregate data length of the data that the SCSI layer
    logically "presents" to the iSCSI layer for a Data-In or Data-Out
    transfer in the context of a SCSI task.  For a bidirectional task,
    there are two SPDTL values -- one for Data-In and one for Data-
    Out.  Note that the notion of "presenting" includes immediate data
    per the data transfer model in [SAM2], and excludes overlapping
    data transfers, if any, requested by the SCSI layer.
 Third-party
    A term used in this document to denote nexus objects (I_T or
    I_T_L) and iSCSI sessions that reap the side effects of actions
    that take place in the context of a separate iSCSI session, while
    being third parties to the action that caused the side effects.
    One example of a third-party session is an iSCSI session hosting

Chadalapaka Standards Track [Page 3] RFC 5048 iSCSI Corrections and Clarifications October 2007

    an I_T_L nexus to an LU that is reset with an LU Reset TMF via a
    separate I_T nexus.
 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

 Acronym        Definition
 -------------------------------------------------------------
 EDTL           Expected Data Transfer Length
 IANA           Internet Assigned Numbers Authority
 IETF           Internet Engineering Task Force
 I/O            Input - Output
 IP             Internet Protocol
 iSCSI          Internet SCSI
 iSER           iSCSI Extensions for RDMA
 ITT            Initiator Task Tag
 LO             Leading Only
 LU             Logical Unit
 LUN            Logical Unit Number
 PDU            Protocol Data Unit
 RDMA           Remote Direct Memory Access
 R2T            Ready To Transfer
 R2TSN          Ready To Transfer Sequence Number
 RFC            Request For Comments
 SAM            SCSI Architecture Model
 SCSI           Small Computer Systems Interface

Chadalapaka Standards Track [Page 4] RFC 5048 iSCSI Corrections and Clarifications October 2007

 SN             Sequence Number
 SNACK          Selective Negative Acknowledgment - also
                Sequence Number Acknowledgement for data
 TCP            Transmission Control Protocol
 TMF            Task Management Function
 TTT            Target Transfer Tag
 UA             Unit Attention

2.3. Clarifications, Changes, and New Semantics

 This document specifies certain changes to [RFC3720] semantics as
 well as defines new iSCSI semantics.  In addition, this document also
 clarifies the [RFC3720] semantics.  This section summarizes the
 contents of the document, categorizing each section into one or more
 of a clarification, change, or new semantic.
    Section 3.1.1: Clarification on iSCSI residuals computation
    general principles
    Section 3.1.2: Clarification on iSCSI residuals computation with
    an example
    Section 3.2: Clarification on R2T ordering requirements
    Section 3.3: New Semantics for Response Ordering in multi-
    connection iSCSI sessions
    Section 4.1.2: Clarifications, changes, and new semantics on
    multi-task abort semantics that all implementations must comply
    with
    Section 4.1.3: Changes and new semantics (FastAbort semantics) on
    multi-task abort semantics that implementations should use for
    faster error recovery
    Section 4.1.3.1: Changes in iSCSI clearing effects semantics
    resulting from new FastAbort semantics
    Section 4.1.4: New Semantics on third-party session interactions
    with the new FastAbort semantics

Chadalapaka Standards Track [Page 5] RFC 5048 iSCSI Corrections and Clarifications October 2007

    Section 4.1.5: Clarification on implementation considerations
    related to outstanding data transfers in order to realize correct
    iSCSI protocol behavior
    Section 4.1.6: Clarification on the intent behind FastAbort
    semantics (not clarifications to [RFC3720] semantics)
    Section 5.1: Clarification on error recovery semantics as
    applicable to Discovery sessions
    Section 5.2.1: Clarification and new semantics on applying the
    Initiator Session Identifier (ISID) RULE ([RFC3720]) to Unnamed
    Discovery Sessions
    Section 5.2.2: Clarification on applying the ISID RULE to Named
    Discovery Sessions
    Section 5.3: Clarification on allowed PDU types and target Logout
    notification behavior on a Discovery session
    Section 6.1: Clarification on the legality of the Target Portal
    Group Tag (TPGT) value of zero
    Section 6.2: Clarification on the negotiating order of SessionType
    with respect to other keys
    Section 6.3: Clarification on the NotUnderstood negotiation
    response on declarative keys and the implied semantics
    Section 6.4: Clarification on the number of legal outstanding
    negotiation PDUs (Text or Login-related)
    Section 7.1: Clarification on usage of the ITT value of 0xffffffff
    Section 7.2: Clarification on what constitutes format errors for
    the purpose of error recovery defined in [RFC3720]
    Section 7.3: Change in error recovery semantics for the case of
    discarding unsolicited PDUs
    Section 7.4: Clarification on the intended level of error checking
    on inbound PDUs
    Section 8.1: New semantics for a new AsyncEvent code
    Section 8.2: Change of legal status for Reject reason code 0x0b;
    it is now deprecated

Chadalapaka Standards Track [Page 6] RFC 5048 iSCSI Corrections and Clarifications October 2007

    Section 9.1: New semantics for a new text key TaskReporting

3. iSCSI Semantics for SCSI Tasks

3.1. Residual Handling

 Section 10.4.1 of [RFC3720] defines the notion of "residuals" and
 specifies how the residual information should be encoded into the
 SCSI Response PDU in the Counts and Flags fields.  Section 3.1.1
 clarifies the intent of [RFC3720] and explains the general
 principles.  Section 3.1.2 describes the residual handling in the
 REPORT LUNS scenario.

3.1.1. Overview

 SCSI-Presented Data Transfer Length (SPDTL) is the term this document
 uses (see Section 1.1 for definition) to represent the aggregate data
 length that the target SCSI layer attempts to transfer using the
 local iSCSI layer for a task.  Expected Data Transfer Length (EDTL)
 is the iSCSI term that represents the length of data that the iSCSI
 layer expects to transfer for a task.  EDTL is specified in the SCSI
 Command PDU.
 When SPDTL = EDTL for a task, the target iSCSI layer completes the
 task with no residuals.  Whenever SPDTL differs from EDTL for a task,
 that task is said to have a residual.
 If SPDTL > EDTL for a task, iSCSI Overflow MUST be signaled in the
 SCSI Response PDU as specified in [RFC3720].  The Residual Count MUST
 be set to the numerical value of (SPDTL - EDTL).
 If SPDTL < EDTL for a task, iSCSI Underflow MUST be signaled in the
 SCSI Response PDU as specified in [RFC3720].  The Residual Count MUST
 be set to the numerical value of (EDTL - SPDTL).
 Note that the Overflow and Underflow scenarios are independent of
 Data-In and Data-Out.  Either scenario is logically possible in
 either direction of data transfer.

3.1.2. SCSI REPORT LUNS and Residual Overflow

 This section discusses the residual overflow issues citing the
 example of the SCSI REPORT LUNS command.  Note however that there are
 several SCSI commands (e.g., INQUIRY) with ALLOCATION LENGTH fields
 following the same underlying rules.  The semantics in the rest of
 the section apply to all such SCSI commands.

Chadalapaka Standards Track [Page 7] RFC 5048 iSCSI Corrections and Clarifications October 2007

 The specification of the SCSI REPORT LUNS command requires that the
 SCSI target limit the amount of data transferred to a maximum size
 (ALLOCATION LENGTH) provided by the initiator in the REPORT LUNS CDB.
 If the Expected Data Transfer Length (EDTL) in the iSCSI header of
 the SCSI Command PDU for a REPORT LUNS command is set to at least as
 large as that ALLOCATION LENGTH, the SCSI layer truncation prevents
 an iSCSI Residual Overflow from occurring.  A SCSI initiator can
 detect that such truncation has occurred via other information at the
 SCSI layer.  The rest of the section elaborates this required
 behavior.
 iSCSI uses the (O) bit (bit 5) in the Flags field of the SCSI
 Response and the last SCSI Data-In PDUs to indicate that an iSCSI
 target was unable to transfer all of the SCSI data for a command to
 the initiator because the amount of data to be transferred exceeded
 the EDTL in the corresponding SCSI Command PDU (see Section 10.4.1 of
 [RFC3720]).
 The SCSI REPORT LUNS command requests a target SCSI layer to return a
 logical unit inventory (LUN list) to the initiator SCSI layer (see
 Section 6.21 of SPC-3 [SPC3]).  The size of this LUN list may not be
 known to the initiator SCSI layer when it issues the REPORT LUNS
 command; to avoid transferring more LUN list data than the initiator
 is prepared for, the REPORT LUNS CDB contains an ALLOCATION LENGTH
 field to specify the maximum amount of data to be transferred to the
 initiator for this command.  If the initiator SCSI layer has under-
 estimated the number of logical units at the target, it is possible
 that the complete logical unit inventory does not fit in the
 specified ALLOCATION LENGTH.  In this situation, Section 4.3.3.6 in
 [SPC3] requires that the target SCSI layer "shall terminate transfers
 to the Data-In Buffer" when the number of bytes specified by the
 ALLOCATION LENGTH field have been transferred.
 Therefore, in response to a REPORT LUNS command, the SCSI layer at
 the target presents at most ALLOCATION LENGTH bytes of data (logical
 unit inventory) to iSCSI for transfer to the initiator.  For a REPORT
 LUNS command, if the iSCSI EDTL is at least as large as the
 ALLOCATION LENGTH, the SCSI truncation ensures that the EDTL will
 accommodate all of the data to be transferred.  If all of the logical
 unit inventory data presented to the iSCSI layer -- i.e., the data
 remaining after any SCSI truncation -- is transferred to the
 initiator by the iSCSI layer, an iSCSI Residual Overflow has not
 occurred and the iSCSI (O) bit MUST NOT be set in the SCSI Response
 or final SCSI Data-Out PDU.  This is not a new requirement but is
 already required by the combination of [RFC3720] with the
 specification of the REPORT LUNS command in [SPC3].  However, if the
 iSCSI EDTL is larger than the ALLOCATION LENGTH in this scenario,
 note that the iSCSI Underflow MUST be signaled in the SCSI Response

Chadalapaka Standards Track [Page 8] RFC 5048 iSCSI Corrections and Clarifications October 2007

 PDU.  An iSCSI Underflow MUST also be signaled when the iSCSI EDTL is
 equal to the ALLOCATION LENGTH but the logical unit inventory data
 presented to the iSCSI layer is smaller than the ALLOCATION LENGTH.
 The LUN LIST LENGTH field in the logical unit inventory (the first
 field in the inventory) is not affected by truncation of the
 inventory to fit in ALLOCATION LENGTH; this enables a SCSI initiator
 to determine that the received inventory is incomplete by noticing
 that the LUN LIST LENGTH in the inventory is larger than the
 ALLOCATION LENGTH that was sent in the REPORT LUNS CDB.  A common
 initiator behavior in this situation is to re-issue the REPORT LUNS
 command with a larger ALLOCATION LENGTH.

3.2. R2T Ordering

 Section 10.8 in [RFC3720] says the following:
    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 connection, outstanding R2Ts MUST be
    fulfilled by the initiator in the order in which they were
    received.
 The quoted [RFC3720] text was unclear on the scope of applicability
 -- either per task, or across all tasks on a connection -- and may be
 interpreted as either.  This section is intended to clarify that the
 scope of applicability of the quoted text is a task.  No R2T ordering
 relationship -- either in generation at the target or in fulfilling
 at the initiator -- across tasks is implied.  That is, outstanding
 R2Ts within a task MUST be fulfilled by the initiator in the order in
 which they were received on a connection.

3.3. Model Assumptions for Response Ordering

 Whenever an iSCSI session is composed of multiple connections, the
 Response PDUs (task responses or TMF responses) originating in the
 target SCSI layer are distributed onto the multiple connections by
 the target iSCSI layer according to iSCSI connection allegiance
 rules.  This process generally may not preserve the ordering of the
 responses by the time they are delivered to the initiator SCSI layer.
 Since ordering is not expected across SCSI responses anyway, this
 approach works fine in the general case.  However, to address the
 special cases where some ordering is desired by the SCSI layer, the
 following "Response Fence" semantics are defined with respect to
 handling SCSI response messages as they are handed off from the SCSI
 protocol layer to the iSCSI layer.

Chadalapaka Standards Track [Page 9] RFC 5048 iSCSI Corrections and Clarifications October 2007

3.3.1. Model Description

 The target SCSI protocol layer hands off the SCSI response messages
 to the target iSCSI layer by invoking the "Send Command Complete"
 protocol data service ([SAM2], clause 5.4.2) and "Task Management
 Function Executed" ([SAM2], clause 6.9) service.  On receiving the
 SCSI response message, the iSCSI layer exhibits the Response Fence
 behavior for certain SCSI response messages (Section 3.3.3 describes
 the specific instances where the semantics must be realized).
 Whenever the Response Fence behavior is required for a SCSI response
 message, the target iSCSI layer MUST ensure that the following
 conditions are met in delivering the response message to the
 initiator iSCSI layer:
 (1) Response with Response Fence MUST be delivered chronologically
     after all the "preceding" responses on the I_T_L nexus, if the
     preceding responses are delivered at all, to the initiator iSCSI
     layer.
 (2) Response with Response Fence MUST be delivered chronologically
     prior to all the "following" responses on the I_T_L nexus.
 The "preceding" and "following" notions refer to the order of handoff
 of a response message from the target SCSI protocol layer to the
 target iSCSI layer.

3.3.2. iSCSI Semantics with the Interface Model

 Whenever the TaskReporting key (Section 9.1) is negotiated to
 ResponseFence or FastAbort for an iSCSI session and the Response
 Fence behavior is required for a SCSI response message, the target
 iSCSI layer MUST perform the actions described in this section for
 that session.
    a) If it is a single-connection session, no special processing is
       required.  The standard SCSI Response PDU build and dispatch
       process happens.
    b) If it is a multi-connection session, the target iSCSI layer
       takes note of the last-sent and unacknowledged StatSN on each
       of the connections in the iSCSI session, and waits for an
       acknowledgement (NOP-In PDUs MAY be used to solicit
       acknowledgements as needed in order to accelerate this process)
       of each such StatSN to clear the fence.  The SCSI response
       requiring Response Fence behavior MUST NOT be sent to the
       initiator before acknowledgements are received for each of the
       unacknowledged StatSNs.

Chadalapaka Standards Track [Page 10] RFC 5048 iSCSI Corrections and Clarifications October 2007

    c) The target iSCSI layer must wait for an acknowledgement of the
       SCSI Response PDU that carried the SCSI response requiring the
       Response Fence behavior.  The fence MUST be considered cleared
       only after receiving the acknowledgement.
    d) All further status processing for the LU is resumed only after
       clearing the fence.  If any new responses for the I_T_L nexus
       are received from the SCSI layer before the fence is cleared,
       those Response PDUs MUST be held and queued at the iSCSI layer
       until the fence is cleared.

3.3.3. Current List of Fenced Response Use Cases

 This section lists the fenced response use cases that iSCSI
 implementations MUST comply with.  However, this is not an exhaustive
 enumeration.  It is expected that as SCSI protocol specifications
 evolve, the specifications will specify when response fencing is
 required on a case-by-case basis.
 Whenever the TaskReporting key (Section 9.1) is negotiated to
 ResponseFence or FastAbort for an iSCSI session, the target iSCSI
 layer MUST assume that the Response Fence is required for the
 following SCSI completion messages:
    1. The first completion message carrying the UA after the multi-
       task abort on issuing and third-party sessions.  See Section
       4.1.1 for related TMF discussion.
    2. The TMF Response carrying the multi-task TMF Response on the
       issuing session.
    3. The completion message indicating ACA establishment on the
       issuing session.
    4. The first completion message carrying the ACA ACTIVE status
       after ACA establishment on issuing and third-party sessions.
    5. The TMF Response carrying the Clear ACA response on the issuing
       session.
    6. The response to a PERSISTENT RESERVE OUT/PREEMPT AND ABORT
       command.
 Note: Due to the absence of ACA-related fencing requirements in
 [RFC3720], initiator implementations SHOULD NOT use ACA on multi-
 connection iSCSI sessions to targets complying only with [RFC3720].
 Initiators that want to employ ACA on multi-connection iSCSI sessions

Chadalapaka Standards Track [Page 11] RFC 5048 iSCSI Corrections and Clarifications October 2007

 SHOULD first assess response-fencing behavior via negotiating for
 ResponseFence or FastAbort values for the TaskReporting (Section 9.1)
 key.

4. Task Management

4.1. Requests Affecting Multiple Tasks

 This section clarifies and updates the original text in Section
 10.6.2 of [RFC3720].  The clarified semantics (Section 4.1.2) are a
 superset of the protocol behavior required in the original text and
 all iSCSI implementations MUST support the new behavior.  The updated
 semantics (Section 4.1.3) on the other hand are mandatory only when
 the new key TaskReporting (Section 9.1) is negotiated to "FastAbort".

4.1.1. Scope of Affected Tasks

 This section defines the notion of "affected tasks" in multi-task
 abort scenarios.  Scope definitions in this section apply to both the
 clarified protocol behavior (Section 4.1.2) and the updated protocol
 behavior (Section 4.1.3).
    ABORT TASK SET: All outstanding tasks for the I_T_L nexus
       identified by the LUN field in the ABORT TASK SET TMF Request
       PDU.
    CLEAR TASK SET: All outstanding tasks in the task set for the LU
       identified by the LUN field in the CLEAR TASK SET TMF Request
       PDU.  See [SPC3] for the definition of a "task set".
    LOGICAL UNIT RESET: All outstanding tasks from all initiators for
       the LU identified by the LUN field in the LOGICAL UNIT RESET
       Request PDU.
    TARGET WARM RESET/TARGET COLD RESET: All outstanding tasks from
       all initiators across all LUs to which the TMF-issuing session
       has access on the SCSI target device hosting the iSCSI session.
 Usage: An "ABORT TASK SET TMF Request PDU" in the preceding text is
 an iSCSI TMF Request PDU with the "Function" field set to "ABORT TASK
 SET" as defined in [RFC3720].  Similar usage is employed for other
 scope descriptions.

Chadalapaka Standards Track [Page 12] RFC 5048 iSCSI Corrections and Clarifications October 2007

4.1.2. Clarified Multi-Task Abort Semantics

 All iSCSI implementations MUST support the protocol behavior defined
 in this section as the default behavior.  The execution of ABORT TASK
 SET, CLEAR TASK SET, LOGICAL UNIT RESET, TARGET WARM RESET, and
 TARGET COLD RESET TMF Requests consists of the following sequence of
 actions in the specified order on the specified party.
 The initiator iSCSI layer:
    a. MUST continue to respond to each TTT received for the affected
       tasks.
    b. SHOULD process any responses received for affected tasks in the
       normal fashion.  This is acceptable because the responses are
       guaranteed to have been sent prior to the TMF response.
    c. SHOULD receive the TMF Response concluding all the tasks in the
       set of affected tasks unless the initiator has done something
       (e.g., LU reset, connection drop) that may prevent the TMF
       Response from being sent or received.  The initiator MUST thus
       conclude all affected tasks as part of this step in either
       case, and MUST discard any TMF Response received after the
       affected tasks are concluded.
 The target iSCSI layer:
    a. MUST wait for responses on currently valid target-transfer tags
       of the affected tasks from the issuing initiator.  MAY wait for
       responses on currently valid target-transfer tags of the
       affected tasks from third-party initiators.
    b. MUST wait (concurrent with the wait in Step a) for all commands
       of the affected tasks to be received based on the CmdSN
       ordering.  SHOULD NOT wait for new commands on third-party
       affected sessions -- only the instantiated tasks have to be
       considered for the purpose of determining the affected tasks.
       In the case of target-scoped requests (i.e., TARGET WARM RESET
       and TARGET COLD RESET), all of the commands that are not yet
       received on the issuing session in the command stream however
       can be considered to have been received with no command waiting
       period -- i.e., the entire CmdSN space up to the CmdSN of the
       task management function can be "plugged".
    c. MUST propagate the TMF request to and receive the response from
       the target SCSI layer.

Chadalapaka Standards Track [Page 13] RFC 5048 iSCSI Corrections and Clarifications October 2007

    d. MUST provide the Response Fence behavior for the TMF Response
       on the issuing session as specified in Section 3.3.2.
    e. MUST provide the Response Fence behavior on the first post-TMF
       Response on third-party sessions as specified in Section 3.3.2.
       If some tasks originate from non-iSCSI I_T_L nexuses, then the
       means by which the target ensures that all affected tasks have
       returned their status to the initiator are defined by the
       specific non-iSCSI transport protocol(s).
 Technically, the TMF servicing is complete in Step d.  Data transfers
 corresponding to terminated tasks may however still be in progress on
 third-party iSCSI sessions even at the end of Step e.  The TMF
 Response MUST NOT be sent by the target iSCSI layer before the end of
 Step d, and MAY be sent at the end of Step d despite these
 outstanding data transfers until after Step e.

4.1.3. Updated Multi-Task Abort Semantics

 Protocol behavior defined in this section MUST be implemented by all
 iSCSI implementations complying with this document.  Protocol
 behavior defined in this section MUST be exhibited by iSCSI
 implementations on an iSCSI session when they negotiate the
 TaskReporting (Section 9.1) key to "FastAbort" on that session.  The
 execution of ABORT TASK SET, CLEAR TASK SET, LOGICAL UNIT RESET,
 TARGET WARM RESET, and TARGET COLD RESET TMF Requests consists of the
 following sequence of actions in the specified order on the specified
 party.
 The initiator iSCSI layer:
    a. MUST NOT send any more Data-Out PDUs for affected tasks on the
       issuing connection of the issuing iSCSI session once the TMF is
       sent to the target.
    b. SHOULD process any responses received for affected tasks in the
       normal fashion.  This is acceptable because the responses are
       guaranteed to have been sent prior to the TMF response.
    c. MUST respond to each Async Message PDU with AsyncEvent=5 as
       defined in Section 8.1.
    d. MUST treat the TMF response as terminating all affected tasks
       for which responses have not been received, and MUST discard
       any responses for affected tasks received after the TMF
       response is passed to the SCSI layer (although the semantics

Chadalapaka Standards Track [Page 14] RFC 5048 iSCSI Corrections and Clarifications October 2007

       defined in this section ensure that such an out-of-order
       scenario will never happen with a compliant target
       implementation).
 The target iSCSI layer:
    a. MUST wait for all commands of the affected tasks to be received
       based on the CmdSN ordering on the issuing session.  SHOULD NOT
       wait for new commands on third-party affected sessions -- only
       the instantiated tasks have to be considered for the purpose of
       determining the affected tasks.  In the case of target-scoped
       requests (i.e., TARGET WARM RESET and TARGET COLD RESET), all
       the commands that are not yet received on the issuing session
       in the command stream can be considered to have been received
       with no command waiting period -- i.e., the entire CmdSN space
       up to the CmdSN of the task management function can be
       "plugged".
    b. MUST propagate the TMF request to and receive the response from
       the target SCSI layer.
    c. MUST leave all active "affected TTTs" (i.e., active TTTs
       associated with affected tasks) valid.
    d. MUST send an Asynchronous Message PDU with AsyncEvent=5
       (Section 8.1) on:
        i) each connection of each third-party session to which at
           least one affected task is allegiant if
           TaskReporting=FastAbort is operational on that third-party
           session, and
       ii) each connection except the issuing connection of the
           issuing session that has at least one allegiant affected
           task.
    If there are multiple affected LUs (say, due to a target reset),
    then one Async Message PDU MUST be sent for each such LU on each
    connection that has at least one allegiant affected task.  The LUN
    field in the Asynchronous Message PDU MUST be set to match the LUN
    for each such LU.
    e. MUST address the Response Fence flag on the TMF Response on the
       issuing session as defined in Section 3.3.2.
    f. MUST address the Response Fence flag on the first post-TMF
       Response on third-party sessions as defined in Section 3.3.2.
       If some tasks originate from non-iSCSI I_T_L nexuses, then the

Chadalapaka Standards Track [Page 15] RFC 5048 iSCSI Corrections and Clarifications October 2007

       means by which the target ensures that all affected tasks have
       returned their status to the initiator are defined by the
       specific non-iSCSI transport protocol(s).
    g. MUST free up the affected TTTs (and STags, if applicable) and
       the corresponding buffers, if any, once it receives each
       associated NOP-Out acknowledgement that the initiator generated
       in response to each Async Message.
 Technically, the TMF servicing is complete in Step e.  Data transfers
 corresponding to terminated tasks may however still be in progress
 even at the end of Step f.  A TMF Response MUST NOT be sent by the
 target iSCSI layer before the end of Step e, and MAY be sent at the
 end of Step e despite these outstanding Data transfers until Step g.
 Step g specifies an event to free up any such resources that may have
 been reserved to support outstanding data transfers.

4.1.3.1. Clearing Effects Update

 Appendix F.1 of [RFC3720] specifies the clearing effects of target
 and LU resets on "Incomplete TTTs" as "Y".  This meant that a target
 warm reset or a target cold reset or an LU reset would clear the
 active TTTs upon completion.  However, the TaskReporting=FastAbort
 (Section 9.1) semantics defined by this section do not guarantee that
 the active TTTs are cleared by the end of the reset operations.  In
 fact, the new semantics are designed to allow clearing the TTTs in a
 "lazy" fashion after the TMF Response is delivered.  Thus, when
 TaskReporting=FastAbort is operational on a session, the clearing
 effects of reset operations on "Incomplete TTTs" is "N".

4.1.4. Affected Tasks Shared across RFC 3720 and FastAbort Sessions

 If an iSCSI target implementation is capable of supporting
 TaskReporting=FastAbort functionality (Section 9.1), it may end up in
 a situation where some sessions have TaskReporting=RFC3720
 operational (RFC 3720 sessions) while some other sessions have
 TaskReporting=FastAbort operational (FastAbort sessions) even while
 accessing a shared set of affected tasks (Section 4.1.1).
 If the issuing session is an RFC 3720 session, the iSCSI target
 implementation is FastAbort-capable, and the third-party affected
 session is a FastAbort session, the following behavior SHOULD be
 exhibited by the iSCSI target layer:
    a. Between Steps c and d of the target behavior in Section 4.1.2,
       send an Asynchronous Message PDU with AsyncEvent=5 (Section
       8.1) on each connection of each third-party session to which at
       least one affected task is allegiant.  If there are multiple

Chadalapaka Standards Track [Page 16] RFC 5048 iSCSI Corrections and Clarifications October 2007

       affected LUs, then send one Async Message PDU for each such LU
       on each connection that has at least one allegiant affected
       task.  When sent, the LUN field in the Asynchronous Message PDU
       MUST be set to match the LUN for each such LU.
    b. After Step e of the target behavior in Section 4.1.2, free up
       the affected TTTs (and STags, if applicable) and the
       corresponding buffers, if any, once each associated NOP-Out
       acknowledgement is received that the third-party initiator
       generated in response to each Async Message sent in Step a.
 If the issuing session is a FastAbort session, the iSCSI target
 implementation is FastAbort-capable, and the third-party affected
 session is an RFC 3720 session, the following behavior MUST be
 exhibited by the iSCSI target layer: Asynchronous Message PDUs MUST
 NOT be sent on the third-party session to prompt the FastAbort
 behavior.
 If the third-party affected session is a FastAbort session and the
 issuing session is a FastAbort session, the initiator in the third-
 party role MUST respond to each Async Message PDU with AsyncEvent=5
 as defined in Section 8.1.  Note that an initiator MAY thus receive
 these Async Messages on a third-party affected session even if the
 session is a single-connection session.

4.1.5. Implementation Considerations

 Both in clarified semantics (Section 4.1.2) and updated semantics
 (Section 4.1.3), there may be outstanding data transfers even after
 the TMF completion is reported on the issuing session.  In the case
 of iSCSI/iSER [iSER], these would be tagged data transfers for STags
 not owned by any active tasks.  Whether or not real buffers support
 these data transfers is implementation-dependent.  However, the data
 transfers logically MUST be silently discarded by the target iSCSI
 layer in all cases.  A target MAY, on an implementation-defined
 internal timeout, also choose to drop the connections on which it did
 not receive the expected Data-Out sequences (Section 4.1.2) or NOP-
 Out acknowledgements (Section 4.1.3) so as to reclaim the associated
 buffer, STag, and TTT resources as appropriate.

4.1.6. Rationale behind the New Semantics

 There are fundamentally three basic objectives behind the semantics
 specified in Sections 4.1.2 and 4.1.3.
    1. Maintaining an ordered command flow I_T nexus abstraction to
       the target SCSI layer even with multi-connection sessions.

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       o  Target iSCSI processing of a TMF request must maintain the
          single flow illusion.  Target behavior in Step b of Section
          4.1.2 and Step a of Section 4.1.3 correspond to this
          objective.
    2. Maintaining a single ordered response flow I_T nexus
       abstraction to the initiator SCSI layer even with multi-
       connection sessions when one response (i.e., TMF response)
       could imply the status of other unfinished tasks from the
       initiator's perspective.
       o  The target must ensure that the initiator does not see "old"
          task responses (that were placed on the wire chronologically
          earlier than the TMF Response) after seeing the TMF
          response.  The target behavior in Step d of Section 4.1.2
          and Step e of Section 4.1.3 correspond to this objective.
       o  Whenever the result of a TMF action is visible across
          multiple I_T_L nexuses, [SAM2] requires the SCSI device
          server to trigger a UA on each of the other I_T_L nexuses.
          Once an initiator is notified of such an UA, the application
          client on the receiving initiator is required to clear its
          task state (clause 5.5 in [SAM2]) for the affected tasks.
          It would thus be inappropriate to deliver a SCSI Response
          for a task after the task state is cleared on the initiator,
          i.e., after the UA is notified.  The UA notification
          contained in the first SCSI Response PDU on each affected
          Third-party I_T_L nexus after the TMF action thus MUST NOT
          pass the affected task responses on any of the iSCSI
          sessions accessing the LU.  The target behavior in Step e of
          Section 4.1.2 and Step f of Section 4.1.3 correspond to this
          objective.
    3. Draining all active TTTs corresponding to affected tasks in a
       deterministic fashion.
       o  Data-Out PDUs with stale TTTs arriving after the tasks are
          terminated can create a buffer management problem even for
          traditional iSCSI implementations, and is fatal for the
          connection for iSCSI/iSER implementations.  Either the
          termination of affected tasks should be postponed until the
          TTTs are retired (as in Step a of Section 4.1.2), or the
          TTTs and the buffers should stay allocated beyond task
          termination to be deterministically freed up later (as in
          Steps c and g of Section 4.1.3).
 The only other notable optimization is the plugging.  If all tasks on
 an I_T nexus will be aborted anyway (as with a target reset), there

Chadalapaka Standards Track [Page 18] RFC 5048 iSCSI Corrections and Clarifications October 2007

 is no need to wait to receive all commands to plug the CmdSN holes.
 The target iSCSI layer can simply plug all missing CmdSN slots and
 move on with TMF processing.  The first objective (maintaining a
 single ordered command flow) is still met with this optimization
 because the target SCSI layer only sees ordered commands.

5. Discovery Semantics

5.1. Error Recovery for Discovery Sessions

 The negotiation of the key ErrorRecoveryLevel is not required for
 Discovery sessions -- i.e., for sessions that negotiated
 "SessionType=Discovery" -- because the default value of 0 is
 necessary and sufficient for Discovery sessions.  It is however
 possible that some legacy iSCSI implementations might attempt to
 negotiate the ErrorRecoveryLevel key on Discovery sessions.  When
 such a negotiation attempt is made by the remote side, a compliant
 iSCSI implementation MUST propose a value of 0 (zero) in response.
 The operational ErrorRecoveryLevel for Discovery sessions thus MUST
 be 0.  This naturally follows from the functionality constraints that
 [RFC3720] imposes on Discovery sessions.

5.2. Reinstatement Semantics of Discovery Sessions

 Discovery sessions are intended to be relatively short-lived.
 Initiators are not expected to establish multiple Discovery sessions
 to the same iSCSI Network Portal (see [RFC3720]).  An initiator may
 use the same iSCSI Initiator Name and ISID when establishing
 different unique sessions with different targets and/or different
 portal groups.  This behavior is discussed in Section 9.1.1 of
 [RFC3720] and is, in fact, encouraged as conservative reuse of ISIDs.
 The ISID RULE in [RFC3720] states that there must not be more than
 one session with a matching 4-tuple: <InitiatorName, ISID,
 TargetName, TargetPortalGroupTag>.  While the spirit of the ISID RULE
 applies to Discovery sessions the same as it does for Normal
 sessions, note that some Discovery sessions differ from the Normal
 sessions in two important aspects:
    Because [RFC3720] allows a Discovery session to be established
    without specifying a TargetName key in the Login Request PDU (let
    us call such a session an "Unnamed" Discovery session), there is
    no Target Node context to enforce the ISID RULE.
    Portal Groups are defined only in the context of a Target Node.
    When the TargetName key is NULL-valued (i.e., not specified), the
    TargetPortalGroupTag thus cannot be ascertained to enforce the
    ISID RULE.

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 The following sections describe the two scenarios -- Named Discovery
 sessions and Unnamed Discovery sessions -- separately.

5.2.1. Unnamed Discovery Sessions

 For Unnamed Discovery sessions, neither the TargetName nor the
 TargetPortalGroupTag is available to the targets in order to enforce
 the ISID RULE.  So the following rule applies.
 UNNAMED ISID RULE: Targets MUST enforce the uniqueness of the
 following 4-tuple for Unnamed Discovery sessions: <InitiatorName,
 ISID, NULL, TargetAddress>.  The following semantics are implied by
 this uniqueness requirement.
 Targets SHOULD allow concurrent establishment of one Discovery
 session with each of its Network Portals by the same initiator port
 with a given iSCSI Node Name and an ISID.  Each of the concurrent
 Discovery sessions, if established by the same initiator port to
 other Network Portals, MUST be treated as independent sessions --
 i.e., one session MUST NOT reinstate the other.
 A new Unnamed Discovery session that has a matching <InitiatorName,
 ISID, NULL, TargetAddress> to an existing Discovery session MUST
 reinstate the existing Unnamed Discovery session.  Note thus that
 only an Unnamed Discovery session may reinstate an Unnamed Discovery
 session.

5.2.2. Named Discovery Sessions

 For a Named Discovery session, the TargetName key is specified by the
 initiator and thus the target can unambiguously ascertain the
 TargetPortalGroupTag as well.  Since all the four elements of the 4-
 tuple are known, the ISID RULE MUST be enforced by targets with no
 changes from [RFC3720] semantics.  A new session with a matching
 <InitiatorName, ISID, TargetName, TargetPortalGroupTag> thus will
 reinstate an existing session.  Note in this case that any new iSCSI
 session (Discovery or Normal) with the matching 4-tuple may reinstate
 an existing Named Discovery iSCSI session.

5.3. Target PDUs during Discovery

 Targets SHOULD NOT send any responses other than a Text Response and
 Logout Response on a Discovery session, once in Full Feature Phase.
 Implementation Note: A target may simply drop the connection in a
 Discovery session when it would have requested a Logout via an Async
 Message on Normal sessions.

Chadalapaka Standards Track [Page 20] RFC 5048 iSCSI Corrections and Clarifications October 2007

6. Negotiation and Others

6.1. TPGT Values

 [SAM2] and [SAM3] specifications incorrectly note in their
 informative text that TPGT value should be non-zero, although
 [RFC3720] allows the value of zero for TPGT.  This section is to
 clarify that a zero value is expressly allowed as a legal value for
 TPGT.  This discrepancy currently stands corrected in [SAM4].

6.2. SessionType Negotiation

 During the Login Phase, the SessionType key is offered by the
 initiator to choose the type of session it wants to create with the
 target.  The target may accept or reject the offer.  Depending on the
 type of the session, a target may decide on resources to allocate and
 the security to enforce, etc. for the session.  If the SessionType
 key is thus going to be offered as "Discovery", it SHOULD be offered
 in the initial Login request by the initiator.

6.3. Understanding NotUnderstood

 [RFC3720] defines NotUnderstood as a valid answer during a
 negotiation text key exchange between two iSCSI nodes.  NotUnderstood
 has the reserved meaning that the sending side did not understand the
 proposed key semantics.  This section seeks to clarify that
 NotUnderstood is a valid answer for both declarative and negotiated
 keys.  The general iSCSI philosophy is that comprehension precedes
 processing for any iSCSI key.  A proposer of an iSCSI key, negotiated
 or declarative, in a text key exchange MUST thus be able to properly
 handle a NotUnderstood response.
 The proper way to handle a NotUnderstood response depends on where
 the key is specified and whether the key is declarative vs.
 negotiated.  All keys defined in [RFC3720] MUST be supported by all
 compliant implementations; a NotUnderstood answer on any of the
 [RFC3720] keys therefore MUST be considered a protocol error and
 handled accordingly.  For all other later keys, a NotUnderstood
 answer concludes the negotiation for a negotiated key whereas for a
 declarative key, a NotUnderstood answer simply informs the declarer
 of a lack of comprehension by the receiver.
 In either case, a NotUnderstood answer always requires that the
 protocol behavior associated with that key not be used within the
 scope of the key (connection/session) by either side.

Chadalapaka Standards Track [Page 21] RFC 5048 iSCSI Corrections and Clarifications October 2007

6.4. Outstanding Negotiation Exchanges

 There was some uncertainty around the number of outstanding Login
 Response PDUs on a connection.  [RFC3720] offers the analogy of SCSI
 linked commands to Login and Text negotiations in Sections 5.3 and
 10.10.3, respectively, but does not make it fully explicit.  This
 section is to offer a clarification in this regard.
 There MUST NOT be more than one outstanding Login Request, Login
 Response, Text Request, or Text Response PDU on an iSCSI connection.
 An outstanding PDU in this context is one that has not been
 acknowledged by the remote iSCSI side.

7. iSCSI Error Handling and Recovery

7.1. ITT

 An ITT value of 0xffffffff is reserved and MUST NOT be assigned for a
 task by the initiator.  The only instance in which it may be seen on
 the wire is in a target-initiated NOP-In PDU (and in the initiator
 response to that PDU, if necessary).  Section 10.19 in [RFC3720]
 mentions this in passing but is noted here again to make it obvious
 since the semantics apply to the initiators in general.

7.2. Format Errors

 Section 6.6 of [RFC3720] discusses format error handling.  This
 section elaborates on the "inconsistent" PDU field contents noted in
 [RFC3720].
 All initiator-detected PDU construction errors MUST be considered as
 format errors.  Some examples of such errors are:
  1. NOP-In with a valid TTT but an invalid LUN
  1. NOP-In with a valid ITT (i.e., a NOP-In response) and also a

valid TTT

  1. SCSI Response PDU with Status=CHECK CONDITION, but

DataSegmentLength = 0

7.3. Digest Errors

 Section 6.7 of [RFC3720] discusses digest error handling.  It states
 that "No further action is necessary for initiators if the discarded
 PDU is an unsolicited PDU (e.g., Async, Reject)" on detecting a
 payload digest error.  This is incorrect.

Chadalapaka Standards Track [Page 22] RFC 5048 iSCSI Corrections and Clarifications October 2007

 An Asynchronous Message PDU or a Reject PDU carries the next StatSN
 value on an iSCSI connection, advancing the StatSN.  When an
 initiator discards one of these PDUs due to a payload digest error,
 the entire PDU including the header MUST be discarded.  Consequently,
 the initiator MUST treat the exception like a loss of any other
 solicited response PDU -- i.e., it MUST use one of the following
 options noted in [RFC3720]:
    a) Request PDU retransmission with a status SNACK.
    b) Logout the connection for recovery and continue the tasks on a
       different connection instance.
    c) Logout to close the connection (abort all the commands
       associated with the connection).

7.4. Message Error Checking

 There has been some uncertainty on the extent to which incoming
 messages have to be checked for protocol errors, beyond what is
 strictly required for processing the inbound message.  This section
 addresses this question.
 Unless [RFC3720] or this document requires it, an iSCSI
 implementation is not required to do an exhaustive protocol
 conformance check on an incoming iSCSI PDU.  The iSCSI implementation
 especially is not required to double-check the remote iSCSI
 implementation's conformance to protocol requirements.

8. iSCSI PDUs

8.1. Asynchronous Message

 This section defines additional semantics for the Asynchronous
 Message PDU defined in Section 10.9 of [RFC3720] using the same
 conventions.
 The following new legal value for the AsyncEvent is defined:
 5: all active tasks for 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.
     i) Stop Data-Out transfers on that connection for all active TTTs
        for the affected LUN quoted in the Async Message PDU.

Chadalapaka Standards Track [Page 23] RFC 5048 iSCSI Corrections and Clarifications October 2007

    ii) 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.
 The new AsyncEvent defined in this section however MUST NOT be used
 on an iSCSI session unless the new TaskReporting text key defined in
 Section 9.1 was negotiated to FastAbort on the session.

8.2. Reject

 Section 10.17.1 of [RFC3720] specifies the Reject reason code of 0x0b
 with an explanation of "Negotiation Reset".  At this point, we do not
 see any legitimate iSCSI protocol use case for using this reason
 code.  Thus, reason code 0x0b MUST be considered as deprecated and
 MUST NOT be sent by implementations that comply with the requirements
 of this document.  An implementation receiving reason code 0x0b MUST
 treat it as a negotiation failure that terminates the Login Phase and
 the TCP connection, as specified in Section 6.10 of [RFC3720].
 Section 5.4 of [RFC3720] states:
    Neither the initiator nor the target should attempt to declare or
    negotiate a parameter more than once during any negotiation
    sequence without an intervening operational parameter negotiation
    reset, except for responses to specific keys that explicitly allow
    repeated key declarations (e.g., TargetAddress).
 The deprecation of reason code 0x0b eliminates the possibility of an
 operational parameter negotiation reset, causing the phrase "without
 an intervening operational parameter negotiation reset" in [RFC3720]
 to refer to an impossible event.  The quoted phrase SHOULD be ignored
 by receivers that handle reason code 0x0b in the manner specified in
 this section.

9. Login/Text Operational Text Keys

 This section follows the same conventions as Section 12 of [RFC3720].

9.1. TaskReporting

 Use: LO
 Senders: Initiator and Target
 Scope: SW
 Irrelevant when: SessionType=Discovery
 TaskReporting=<list-of-values>

Chadalapaka Standards Track [Page 24] RFC 5048 iSCSI Corrections and Clarifications October 2007

 Default is RFC3720.
 Result function is AND.
 This key is used to negotiate the task completion reporting semantics
 from the SCSI target.  The following table describes the semantics
 that an iSCSI target MUST support for respective negotiated key
 values.  Whenever this key is negotiated, at least the RFC3720 and
 ResponseFence values MUST be offered as options by the negotiation
 originator.
 +--------------+------------------------------------------+
 | Name         |             Description                  |
 +--------------+------------------------------------------+
 | RFC3720      | RFC 3720-compliant semantics.  Response  |
 |              | fencing is not guaranteed and fast       |
 |              | completion of multi-task aborting is not |
 |              | supported                                |
 +--------------+------------------------------------------+
 | ResponseFence| Response Fence (Section 3.3.1) semantics |
 |              | MUST be supported in reporting task      |
 |              | completions                              |
 +--------------+------------------------------------------+
 | FastAbort    | Updated fast multi-task abort semantics  |
 |              | defined in Section 4.1.3 MUST be         |
 |              | supported.  Support for Response Fence is|
 |              | implied -- i.e., Section 3.3.1 semantics |
 |              | MUST be supported as well                |
 +--------------+------------------------------------------+
 When TaskReporting is not negotiated to FastAbort, the [RFC3720] TMF
 semantics as clarified in Section 4.1.2 MUST be used.

10. Security Considerations

 This document does not introduce any new security considerations
 other than those already noted in [RFC3720].  Consequently, all the
 iSCSI-related security text in [RFC3723] is also directly applicable
 to this document.

Chadalapaka Standards Track [Page 25] RFC 5048 iSCSI Corrections and Clarifications October 2007

11. IANA Considerations

11.1. iSCSI-Related IANA Registries

 This document creates the following iSCSI-related registries for IANA
 to manage.
    1. iSCSI Opcodes
    2. iSCSI Login/Text Keys
    3. iSCSI Asynchronous Events
    4. iSCSI Task Management Function Codes
    5. iSCSI Login Response Status Codes
    6. iSCSI Reject Reason Codes
    7. iSER Opcodes
 Each of the following sections describes a registry, its sub-
 registries if any, and their administration policies in more detail.
 IANA has registered what this document calls the main "registries" as
 sub-registries of a larger iSCSI registry.  However, wherever
 registry-to-sub-registry relationships are specified by this
 document, they have been preserved intact.
 [RFC3720] specifies three iSCSI-related registries -- extended key,
 authentication methods, and digests.  This document recommends that
 these registries be published together with the registries defined by
 this document.  Further, this document recommends that the three
 [RFC3720] registries be listed in between items 6 and 7 in the
 registry list above.

11.2. iSCSI Opcodes

 Name of the registry: "iSCSI Opcodes"
 Namespace details: Numerical values that can fit in one octet with
 the most significant two bits (bits 0 and 1) already designated by
 [RFC3720], bit 0 being reserved and bit 1 for immediate delivery.
 Bit 2 is designated to identify the originator of the opcode.  Bit 2
 = 0 for initiator and Bit 2 = 1 for target.

Chadalapaka Standards Track [Page 26] RFC 5048 iSCSI Corrections and Clarifications October 2007

 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.
 Allocation request guidance to requesters:
    1) If the initiator opcode and target opcode used to identify the
       request and response of a new type of protocol operation are
       requested, assign the same lower five bits (i.e., Bit 3 through
       Bit 7) for both opcodes, e.g., 0x13 and 0x33.
    2) If only the initiator opcode or target opcode is requested to
       identify a one-way protocol message (i.e., request without a
       response or a "response" without a request), assign an unused
       number from the appropriate category (i.e., Bit 2 set to 0 or 1
       for initiator category or target category) and add the other
       pair member (i.e., same opcode with Bit 2 set to 1 or 0,
       respectively) to "no opcode pair is available" list.
    3) If there are no other opcodes available in the appropriate
       "Reserved to IANA" list to assign on a request for a new opcode
       except the reserved opcodes in the "no opcode pair is
       available" list, allocate the opcode from the appropriate
       category (initiator or target) of the "no opcode pair is
       available" list.
 Fields to record in the registry: Assigned value, Who can originate
 (Initiator or Target), Operation Name, and its associated RFC
 reference.
 Initial registry contents:
 0x00, Initiator, NOP-Out, [RFC3720]
 0x01, Initiator, SCSI Command, [RFC3720]
 0x02, Initiator, SCSI Task Management function request, [RFC3720]
 0x03, Initiator, Login Request, [RFC3720]
 0x04, Initiator, Text Request, [RFC3720]
 0x05, Initiator, SCSI Data-Out, [RFC3720]
 0x06, Initiator, Logout Request, [RFC3720]
 0x10, Initiator, SNACK Request, [RFC3720]

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 0x1c-0x1e, Initiator, Vendor specific codes, [RFC3720]
 0x20, Target, NOP-In, [RFC3720]
 0x21, Target, SCSI Response, [RFC3720]
 0x22, Target, SCSI Task Management function response, [RFC3720]
 0x23, Target, Login Response, [RFC3720]
 0x24, Target, Text Response, [RFC3720]
 0x25, Target, SCSI Data-In, [RFC3720]
 0x26, Target, Logout Response, [RFC3720]
 0x31, Target, Ready To Transfer (R2T), [RFC3720]
 0x32, Target, Asynchronous Message, [RFC3720]
 0x3c-0x3e, Target, Vendor specific codes, [RFC3720]
 0x3f, Target, Reject, [RFC3720]
 Reserved to IANA:
     0x07-0x0f, 0x13-0x1b (initiator codes)
     0x27-0x2f, 0x33-0x3b (target codes)
 No opcode pair is available:
     0x11, 0x12, 0x1f (initiator codes)
     0x30 (target codes)
 Allocation Policy:
 Standards Action ([IANA]): This is required for defining the
 semantics of the opcode.
 Expert Review ([IANA]): This is required for selecting the specific
 opcode(s) to allocate in order to ensure compliance with the earlier
 "Allocation request guidance to requesters".

11.3. iSCSI Login/Text Keys

 Name of the registry: "iSCSI Text Keys"
 Namespace details: Key=value pairs with "Key" names in UTF-8 Unicode,
 and the permissible "value" options for the "Key" are Key-dependent.
 [RFC3720] defines the rules on key names and allowed values.

Chadalapaka Standards Track [Page 28] RFC 5048 iSCSI Corrections and Clarifications October 2007

 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 Key per [RFC3720]
 key specification template and the fields to be recorded in the
 registry.
 Assignment policy:
 If the requested Key name is not already assigned and is roughly
 representative of its proposed semantics, it may be assigned to the
 requester.
 Given the arbitrary nature of text strings, there is no maximum
 reserved by IANA for assignment in this registry.
 Fields to record in the registry: Assigned Key Name and its
 associated RFC reference.
 Initial registry contents:
 AuthMethod, [RFC3720]
 HeaderDigest, [RFC3720]
 DataDigest, [RFC3720]
 MaxConnections, [RFC3720]
 SendTargets, [RFC3720]
 TargetName, [RFC3720]
 InitiatorName, [RFC3720]
 TargetAlias, [RFC3720]
 InitiatorAlias, [RFC3720]
 TargetAddress, [RFC3720]
 TargetPortalGroupTag, [RFC3720]
 InitialR2T, [RFC3720]
 ImmediateData, [RFC3720]
 MaxRecvDataSegmentLength, [RFC3720]

Chadalapaka Standards Track [Page 29] RFC 5048 iSCSI Corrections and Clarifications October 2007

 MaxBurstLength, [RFC3720]
 FirstBurstLength, [RFC3720]
 DefaultTime2Wait, [RFC3720]
 DefaultTime2Retain, [RFC3720]
 MaxOutstandingR2T, [RFC3720]
 DataPDUInOrder, [RFC3720]
 DataSequenceInOrder, [RFC3720]
 ErrorRecoveryLevel, [RFC3720]
 SessionType, [RFC3720]
 RDMAExtensions, [iSER]
 TargetRecvDataSegmentLength, [iSER]
 InitiatorRecvDataSegmentLength, [iSER]
 MaxOutstandingUnexpectedPDUs, [iSER]
 TaskReporting, this document
 Allocation Policy:
 Standards Action ([IANA])

11.4. iSCSI Asynchronous Events

 Name of the registry: "iSCSI Asynchronous Events"
 Namespace details: Numerical values that can fit in one octet.
 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 Event 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.

Chadalapaka Standards Track [Page 30] RFC 5048 iSCSI Corrections and Clarifications October 2007

 6-247: range reserved by IANA for assignment in this registry.
 Fields to record in the registry: Assigned Event number, Description
 and its associated RFC reference.
 Initial registry contents:
 0, SCSI Async Event, [RFC3720]
 1, Logout Request, [RFC3720]
 2, Connection drop notification, [RFC3720]
 3, Session drop notification, [RFC3720]
 4, Negotiation Request, [RFC3720]
 5, Task termination, this document
 248-254, Vendor-unique, this document
 255, Vendor-unique, [RFC3720]
 Allocation Policy:
 Standards Action ([IANA])

11.5. iSCSI Task Management Function Codes

 Name of the registry: "iSCSI TMF Codes"
 Namespace details: Numerical values that can fit in 7 bits.
 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 Code 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.
 9-127: range reserved by IANA for assignment in this registry.
 Fields to record in the registry: Assigned Code, Description, and its
 associated RFC reference.

Chadalapaka Standards Track [Page 31] RFC 5048 iSCSI Corrections and Clarifications October 2007

 Initial registry contents:
 1, ABORT TASK, [RFC3720]
 2, ABORT TASK SET, [RFC3720]
 3, CLEAR ACA, [RFC3720]
 4, CLEAR TASK SET, [RFC3720]
 5, LOGICAL UNIT RESET, [RFC3720]
 6, TARGET WARM RESET, [RFC3720]
 7, TARGET COLD RESET, [RFC3720]
 8, TASK REASSIGN, [RFC3720]
 Allocation Policy:
 Standards Action ([IANA])

11.6. iSCSI Login Response Status Codes

 Name of the registry: "iSCSI Login Response Status Codes"
 Namespace details: Numerical values; Status-Class (one octet),
 Status-Detail (one octet) for each possible value of Status-Class
 except for Vendor-Unique Status-Class (0x0f).
 Information that must be provided to assign a new value: An IESG-
 approved specification defining the semantics and interoperability
 requirements of the proposed new Code, its Status-Class affiliation
 (only if a new Status-Detail value is being proposed for a Status-
 Class), Status-Class definition (only if a new Status-Class is being
 proposed), 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.
 4-14 and 16-255: range reserved by IANA for assignment in this
 registry.
 Fields to record in the Status-Class main registry: Assigned Code,
 Description, and its associated RFC reference.

Chadalapaka Standards Track [Page 32] RFC 5048 iSCSI Corrections and Clarifications October 2007

 Fields to record in the Status-Detail sub-registries: Status-Class,
 Assigned Code, Description, and its associated RFC reference.
 Initial registry contents (Status-Class):
 0x00, Success, [RFC3720]
 0x01, Redirection, [RFC3720]
 0x02, Initiator Error, [RFC3720]
 0x03, Target Error, [RFC3720]
 0x0f, Vendor-Unique, this document
 Initial sub-registry contents (Status-Detail for Status-Class=0x00):
 0x00, 0x00, Success, [RFC3720]
 1-255: range reserved by IANA for assignment in Status-Class=0 sub-
 registry.
 Initial sub-registry contents (Status-Detail for Status-Class=0x01):
 0x01, 0x01, Temporary move, [RFC3720]
 0x01, 0x02, Permanent move, [RFC3720]
 3-255: range reserved by IANA for assignment in Status-Class=1 sub-
 registry.
 Initial sub-registry contents (Status-Detail for Status-Class=0x02):
 0x02, 0x00, Miscellaneous, [RFC3720]
 0x02, 0x01, Authentication failure, [RFC3720]
 0x02, 0x02, Authorization failure, [RFC3720]
 0x02, 0x03, Not found, [RFC3720]
 0x02, 0x04, Target removed, [RFC3720]
 0x02, 0x05, Unsupported version, [RFC3720]
 0x02, 0x06, Too many connections, [RFC3720]
 0x02, 0x07, Missing parameter, [RFC3720]

Chadalapaka Standards Track [Page 33] RFC 5048 iSCSI Corrections and Clarifications October 2007

 0x02, 0x08, Can't include in session, [RFC3720]
 0x02, 0x09, Unsupported session type, [RFC3720]
 0x02, 0x0a, Non-existent session, [RFC3720]
 0x02, 0x0b, Invalid during login, [RFC3720]
 12-255: range reserved by IANA for assignment in Status-Class=2 sub-
 registry.
 Initial sub-registry contents (Status-Detail for Status-Class=0x03):
 0x03, 0x00, Target error, [RFC3720]
 0x03, 0x01, Service unavailable, [RFC3720]
 0x03, 0x02, Out of resources, [RFC3720]
 3-255: range reserved by IANA for assignment in Status-Class=3 sub-
 registry.
 Allocation Policy:
 Standards Action ([IANA])

11.7. iSCSI Reject Reason Codes

 Name of the registry: "iSCSI Reject Reason Codes"
 Namespace details: Numerical values that can fit in a single octet.
 Information that must be provided to assign a new value: A published
 specification defining the semantics and interoperability
 requirements of the proposed new Code 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.
 13-255: range reserved by IANA for assignment in this registry.
 Fields to record in the registry: Assigned Code, Description, and its
 associated RFC reference.

Chadalapaka Standards Track [Page 34] RFC 5048 iSCSI Corrections and Clarifications October 2007

 Initial registry contents:
 0x01, Reserved, [RFC3720]
 0x02, Data digest error, [RFC3720]
 0x03, SNACK Reject, [RFC3720]
 0x04, Protocol Error, [RFC3720]
 0x05, Command not supported, [RFC3720]
 0x06, Immediate command reject, [RFC3720]
 0x07, Task in progress, [RFC3720]
 0x08, Invalid data ack, [RFC3720]
 0x09, Invalid PDU field, [RFC3720]
 0x0a, Long op reject, [RFC3720]
 0x0b, "Deprecated reason code", this document
 0x0c, Waiting for Logout, [RFC3720]
 Allocation Policy:
 Standards Action ([IANA])

11.8. iSER Opcodes

 Name of the registry: "iSER Opcodes"
 Namespace details: Numerical values that can fit in 4 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.
 4-15: range reserved by IANA for assignment in this registry.

Chadalapaka Standards Track [Page 35] RFC 5048 iSCSI Corrections and Clarifications October 2007

 Fields to record in the registry: Assigned value, Operation Name, and
 its associated RFC reference.
 Initial registry contents:
 0x1, iSCSI control-type, [iSER]
 0x2, iSER Hello, [iSER]
 0x3, iSER HelloReply, [iSER]
 Allocation Policy:
 Standards Action ([IANA])

12. References

12.1. Normative References

 [RFC3720] Satran, J., Meth, K., Sapuntzakis, C., Chadalapaka, M., and
           E. Zeidner, "Internet Small Computer Systems Interface
           (iSCSI)", RFC 3720, April 2004.
 [SPC3]    ANSI INCITS 408-2005, SCSI Primary Commands-3.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [IANA]    Narten, T. and H. Alvestrand, "Guidelines for Writing an
           IANA Considerations Section in RFCs", BCP 26, RFC 2434,
           October 1998.
 [iSER]    Ko, M., Chadalapaka, M., Hufferd, J., Elzur, U., Shah, H.,
           and P. Thaler, "Internet Small Computer System Interface
           (iSCSI) Extensions for Remote Direct Memory Access (RDMA)",
           RFC 5046, October 2007.

12.2. Informative References

 [RFC3721] Bakke, M., Hafner, J., Hufferd, J., Voruganti, K., and M.
           Krueger, "Internet Small Computer Systems Interface (iSCSI)
           Naming and Discovery", RFC 3721, April 2004.
 [RFC3723] Aboba, B., Tseng, J., Walker, J., Rangan, V., and F.
           Travostino, "Securing Block Storage Protocols over IP", RFC
           3723, April 2004.

Chadalapaka Standards Track [Page 36] RFC 5048 iSCSI Corrections and Clarifications October 2007

 [RFC3722] Bakke, M., "String Profile for Internet Small Computer
           Systems Interface (iSCSI) Names", RFC 3722, April 2004.
 [SAM2]    ANSI INCITS 366-2003, SCSI Architecture Model-2 (SAM-2).
 [SAM3]    ANSI INCITS 402-2005, SCSI Architecture Model-3 (SAM-a3).
 [SAM4]    T10 Project: 1683-D, SCSI Architecture Model-4 (SAM-4),
           Work in Progress.

Acknowledgements

 The IP Storage (IPS) Working Group in the Transport Area of the IETF
 has been responsible for defining the iSCSI protocol (apart from a
 host of other relevant IP Storage protocols).  The editor
 acknowledges the contributions of the entire working group.
 The following individuals directly contributed to identifying
 [RFC3720] issues and/or suggesting resolutions to the issues
 clarified in this document: David Black, Gwendal Grignou, Mike Ko,
 Dmitry Fomichev, Bill Studenmund, Ken Sandars, Bob Russell, Julian
 Satran, Rob Elliott, Joseph Pittman, Somesh Gupta, Eddy Quicksall,
 Paul Koning.  This document benefited from all of these
 contributions.

Editor's Address

 Mallikarjun Chadalapaka
 Hewlett-Packard Company
 8000 Foothills Blvd.
 Roseville, CA 95747-5668, USA
 Phone: +1-916-785-5621
 EMail: cbm@rose.hp.com

Chadalapaka Standards Track [Page 37] RFC 5048 iSCSI Corrections and Clarifications October 2007

Full Copyright Statement

 Copyright (C) The IETF Trust (2007).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
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 attempt made to obtain a general license or permission for the use of
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 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
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Chadalapaka Standards Track [Page 38]

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