💾 Archived View for gemini.bortzmeyer.org › rfc-mirror › rfc7144.txt captured on 2023-06-16 at 17:49:16.
⬅️ Previous capture (2021-11-30)
-=-=-=-=-=-=-
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.
----------------------------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]