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《互联网小型计算机系统接口（iSCSI）协议》 iSCSI，即Internet Small Computer System Interface，是一种在互联网上实现存储区域网络（SAN）的技术，它通过传输控制协议/因特网协议（TCP/IP）来封装并传输小型计算机系统接口（SCSI）命令。SCSI原本是用于本地存储设备的标准，而iSCSI则使其能够跨越网络进行操作，扩展了存储解决方案的可伸缩性和灵活性。 iSCSI协议的设计目标是与标准化的SCSI架构模型（SAM-2）完全兼容，确保在远程位置也能提供与传统SCSI相同的存储服务。RFC 3720首次定义了iSCSI协议，提供了基本的框架和规范。RFC 3721则详细讨论了iSCSI的命名示例和发现技术，这些技术对于在网络中定位和识别存储设备至关重要。随着时间的发展，iSCSI协议不断演进和完善。RFC 3980增加了新的命名格式，使得iSCSI协议支持更多的设备标识方式。接着，RFC 4850引入了一个公共扩展密钥，扩展了iSCSI的功能，增强了安全性和可配置性。而RFC 5048则对原始协议进行了澄清，提出了一些改进和修正，确保了协议的稳定性和效率。本文档将上述RFCs整合为一个单一文档，以消除版本分散带来的困扰，并对整合后的规范进行了额外更新，同时也更新了RFC 3721的内容。这一整合旨在提高iSCSI协议的清晰度，简化其使用和实施，同时保持与IETF社区共识的一致性。 iSCSI协议的实施通常包括以下组件： 1. **发起端（Initiator）**：这通常是服务器或客户端，负责发起SCSI命令。 2. **目标端（Target）**：这是存储设备或存储阵列，接收并响应来自发起端的命令。 3. **TCP/IP网络**：作为数据传输的载体，连接发起端和目标端。 4. **iSCSI名称（IQN）**：每个iSCSI设备都有一个唯一的名称，用于在网络中识别和连接。 iSCSI协议提供了以下关键功能： - **发现服务**：允许设备自动发现网络上的其他iSCSI设备。 - **会话管理**：建立和维护发起端和目标端之间的安全连接。 - **数据块传输**：通过TCP/IP高效地传输大量数据。 - **错误处理**：确保数据的完整性和一致性，通过错误检测和恢复机制。 - **安全特性**：如CHAP（Challenge Handshake Authentication Protocol）用于身份验证，保护存储资源不被未经授权的访问。由于iSCSI基于标准的TCP/IP协议栈，因此可以利用现有的网络基础设施，降低了部署成本。此外，它支持多种服务质量（QoS）策略，可以根据业务需求调整网络带宽和延迟。 iSCSI协议通过将SCSI协议与TCP/IP结合，为分布式环境中的存储管理和数据传输提供了强大且灵活的解决方案，是现代数据中心和云计算环境中不可或缺的一部分。随着技术的持续发展，iSCSI协议将继续优化，以满足日益增长的存储需求和挑战。

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Internet Engineering Task Force (IETF) M. Chadalapaka

Request for Comments: 7143 Microsoft

Obsoletes: 3720, 3980, 4850, 5048 J. Satran

Updates: 3721 Infinidat Ltd.

Category: Standards Track K. Meth

ISSN: 2070-1721 IBM

D. Black

EMC

April 2014

Internet Small Computer System Interface (iSCSI) Protocol

(Consolidated)

Abstract

This document describes a transport protocol for SCSI that works on

top of TCP. The iSCSI protocol aims to be fully compliant with the

standardized SCSI Architecture Model (SAM-2). RFC 3720 defined the

original iSCSI protocol. RFC 3721 discusses iSCSI naming examples

and discovery techniques. Subsequently, RFC 3980 added an additional

naming format to the iSCSI protocol. RFC 4850 followed up by adding

a new public extension key to iSCSI. RFC 5048 offered a number of

clarifications as well as a few improvements and corrections to the

original iSCSI protocol.

This document obsoletes RFCs 3720, 3980, 4850, and 5048 by

consolidating them into a single document and making additional

updates to the consolidated specification. This document also

updates RFC 3721. The text in this document thus supersedes the text

in all the noted RFCs wherever there is a difference in semantics.

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/rfc7143.

Chadalapaka, et al. Standards Track [Page 1]

RFC 7143 iSCSI (Consolidated) April 2014

This document is subject to BCP 78 and the IETF Trust’s Legal

Provisions Relating to IETF Documents

(http://trustee.ietf.org/license-info) in effect on the date of

publication of this document. Please review these documents

carefully, as they describe your rights and restrictions with respect

to this document. Code Components extracted from this document must

include Simplified BSD License text as described in Section 4.e of

the Trust Legal Provisions and are provided without warranty as

described in the Simplified BSD License.

Table of Contents

1. Introduction ...................................................11

2. Acronyms, Definitions, and Document Summary ....................11

2.1. Acronyms ..................................................11

2.2. Definitions ...............................................13

2.3. Summary of Changes ........................................19

2.4. Conventions ...............................................20

3. UML Conventions ................................................20

3.1. UML Conventions Overview ..................................20

3.2. Multiplicity Notion .......................................21

3.3. Class Diagram Conventions .................................22

3.4. Class Diagram Notation for Associations ...................23

3.5. Class Diagram Notation for Aggregations ...................24

3.6. Class Diagram Notation for Generalizations ................25

4. Overview .......................................................25

4.1. SCSI Concepts .............................................25

4.2. iSCSI Concepts and Functional Overview ....................26

4.2.1. Layers and Sessions ................................27

4.2.2. Ordering and iSCSI Numbering .......................28

4.2.2.1. Command Numbering and Acknowledging .......28

4.2.2.2. Response/Status Numbering and

Acknowledging .............................32

4.2.2.3. Response Ordering .........................32

4.2.2.3.1. Need for Response Ordering .....32

4.2.2.3.2. Response Ordering Model

Description ....................33

4.2.2.3.3. iSCSI Semantics with

the Interface Model ............33

4.2.2.3.4. Current List of Fenced

Response Use Cases .............34

4.2.2.4. Data Sequencing ...........................35

Chadalapaka, et al. Standards Track [Page 2]

RFC 7143 iSCSI (Consolidated) April 2014

4.2.3. iSCSI Task Management ..............................36

4.2.3.1. Task Management Overview ..................36

4.2.3.2. Notion of Affected Tasks ..................36

4.2.3.3. Standard Multi-Task Abort Semantics .......37

4.2.3.4. FastAbort Multi-Task Abort Semantics ......38

4.2.3.5. Affected Tasks Shared across

Standard and FastAbort Sessions ...........40

4.2.3.6. Rationale behind the FastAbort Semantics ..41

4.2.4. iSCSI Login ........................................42

4.2.5. iSCSI Full Feature Phase ...........................44

4.2.5.1. Command Connection Allegiance .............44

4.2.5.2. Data Transfer Overview ....................45

4.2.5.3. Tags and Integrity Checks .................46

4.2.5.4. SCSI Task Management during iSCSI

Full Feature Phase ........................47

4.2.6. iSCSI Connection Termination .......................47

4.2.7. iSCSI Names ........................................47

4.2.7.1. iSCSI Name Properties .....................48

4.2.7.2. iSCSI Name Encoding .......................50

4.2.7.3. iSCSI Name Structure ......................51

4.2.7.4. Type "iqn." (iSCSI Qualified Name) ........52

4.2.7.5. Type "eui." (IEEE EUI-64 Format) ..........53

4.2.7.6. Type "naa." (Network Address Authority) ...54

4.2.8. Persistent State ...................................55

4.2.9. Message Synchronization and Steering ...............55

4.2.9.1. Sync/Steering and iSCSI PDU Length ........56

4.3. iSCSI Session Types .......................................56

4.4. SCSI-to-iSCSI Concepts Mapping Model ......................57

4.4.1. iSCSI Architecture Model ...........................58

4.4.2. SCSI Architecture Model ............................59

4.4.3. Consequences of the Model ..........................61

4.4.3.1. I_T Nexus State ...........................62

4.4.3.2. Reservations ..............................63

4.5. iSCSI UML Model ...........................................64

4.6. Request/Response Summary ..................................66

4.6.1. Request/Response Types Carrying SCSI Payload .......66

4.6.1.1. SCSI Command ..............................66

4.6.1.2. SCSI Response .............................66

4.6.1.3. Task Management Function Request ..........67

4.6.1.4. Task Management Function Response .........68

4.6.1.5. SCSI Data-Out and SCSI Data-In ............68

4.6.1.6. Ready To Transfer (R2T) ...................69

4.6.2. Requests/Responses Carrying SCSI and iSCSI

Payload ............................................69

4.6.2.1. Asynchronous Message ......................69

Chadalapaka, et al. Standards Track [Page 3]

RFC 7143 iSCSI (Consolidated) April 2014

4.6.3. Requests/Responses Carrying iSCSI-Only Payload .....69

4.6.3.1. Text Requests and Text Responses ..........69

4.6.3.2. Login Requests and Login Responses ........70

4.6.3.3. Logout Requests and Logout Responses ......71

4.6.3.4. SNACK Request .............................71

4.6.3.5. Reject ....................................71

4.6.3.6. NOP-Out Request and NOP-In Response .......71

5. SCSI Mode Parameters for iSCSI .................................72

6. Login and Full Feature Phase Negotiation .......................72

6.1. Text Format ...............................................73

6.2. Text Mode Negotiation .....................................76

6.2.1. List Negotiations ..................................80

6.2.2. Simple-Value Negotiations ..........................80

6.3. Login Phase ...............................................81

6.3.1. Login Phase Start ..................................84

6.3.2. iSCSI Security Negotiation .........................87

6.3.3. Operational Parameter Negotiation during

the Login Phase ....................................87

6.3.4. Connection Reinstatement ...........................88

6.3.5. Session Reinstatement, Closure, and Timeout ........89

6.3.5.1. Loss of Nexus Notification ................90

6.3.6. Session Continuation and Failure ...................90

6.4. Operational Parameter Negotiation outside the

7. iSCSI Error Handling and Recovery ..............................92

7.1. Overview ..................................................92

7.1.1. Background .........................................92

7.1.2. Goals ..............................................92

7.1.3. Protocol Features and State Expectations ...........93

7.1.4. Recovery Classes ...................................94

7.1.4.1. Recovery Within-command ...................95

7.1.4.2. Recovery Within-connection ................96

7.1.4.3. Connection Recovery .......................96

7.1.4.4. Session Recovery ..........................97

7.1.5. Error Recovery Hierarchy ...........................97

7.2. Retry and Reassign in Recovery ............................99

7.2.1. Usage of Retry .....................................99

7.2.2. Allegiance Reassignment ...........................100

7.3. Usage of Reject PDU in Recovery ..........................101

7.4. Error Recovery Considerations for Discovery Sessions .....102

7.4.1. ErrorRecoveryLevel for Discovery Sessions .........102

7.4.2. Reinstatement Semantics for Discovery Sessions ....102

7.4.2.1. Unnamed Discovery Sessions ...............103

7.4.2.2. Named Discovery Sessions .................103

7.4.3. Target PDUs during Discovery ......................103

Chadalapaka, et al. Standards Track [Page 4]

RFC 7143 iSCSI (Consolidated) April 2014

7.5. Connection Timeout Management ............................104

7.5.1. Timeouts on Transport Exception Events ............104

7.5.2. Timeouts on Planned Decommissioning ...............104

7.6. Implicit Termination of Tasks ............................104

7.7. Format Errors ............................................105

7.8. Digest Errors ............................................106

7.9. Sequence Errors ..........................................107

7.10. Message Error Checking ..................................108

7.11. SCSI Timeouts ...........................................108

7.12. Negotiation Failures ....................................109

7.13. Protocol Errors .........................................110

7.14. Connection Failures .....................................110

7.15. Session Errors ..........................................111

8. State Transitions .............................................112

8.1. Standard Connection State Diagrams .......................112

8.1.1. State Descriptions for Initiators and Targets .....112

8.1.2. State Transition Descriptions for

Initiators and Targets ............................114

8.1.3. Standard Connection State Diagram for an

Initiator .........................................118

8.1.4. Standard Connection State Diagram for a Target ....120

8.2. Connection Cleanup State Diagram for Initiators

and Targets ..............................................122

8.2.1. State Descriptions for Initiators and Targets .....124

8.2.2. State Transition Descriptions for

Initiators and Targets ............................124

8.3. Session State Diagrams ...................................126

8.3.1. Session State Diagram for an Initiator ............126

8.3.2. Session State Diagram for a Target ................127

8.3.3. State Descriptions for Initiators and Targets .....129

8.3.4. State Transition Descriptions for

Initiators and Targets ............................129

9. Security Considerations .......................................131

9.1. iSCSI Security Mechanisms ................................132

9.2. In-Band Initiator-Target Authentication ..................132

9.2.1. CHAP Considerations ...............................134

9.2.2. SRP Considerations ................................136

9.2.3. Kerberos Considerations ...........................136

9.3. IPsec ....................................................137

9.3.1. Data Authentication and Integrity .................137

9.3.2. Confidentiality ...................................138

9.3.3. Policy, Security Associations, and

Cryptographic Key Management ......................139

9.4. Security Considerations for the X#NodeArchitecture Key ...141

9.5. SCSI Access Control Considerations .......................143

Chadalapaka, et al. Standards Track [Page 5]

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